Check if Xcode version is unsupported

Add limited test coverage

.github/workflows/__diagnostics-without-db.yml

@@ -0,0 +1,84 @@
+# Warning: This file is generated automatically, and should not be modified.
+# Instead, please modify the template in the pr-checks directory and run:
+#     pr-checks/sync.sh
+# to regenerate this file.
+
+name: PR Check - Diagnostic export without database
+env:
+  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+  GO111MODULE: auto
+on:
+  push:
+    branches:
+      - main
+      - releases/v*
+  pull_request: {}
+  merge_group:
+    types:
+      - checks_requested
+  schedule:
+    - cron: '0 5 * * *'
+  workflow_dispatch:
+    inputs: {}
+  workflow_call:
+    inputs: {}
+defaults:
+  run:
+    shell: bash
+concurrency:
+  cancel-in-progress: ${{ github.event_name == 'pull_request' || false }}
+  group: diagnostics-without-db-${{github.ref}}
+jobs:
+  diagnostics-without-db:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: ubuntu-latest
+            version: linked
+    name: Diagnostic export without database
+    if: github.triggering_actor != 'dependabot[bot]'
+    permissions:
+      contents: read
+      security-events: read
+    timeout-minutes: 45
+    runs-on: ${{ matrix.os }}
+    steps:
+      # We deliberately need to make this step fail before the database is initialised, but after
+      # some diagnostic has been produced. The simplest way to do that right now is to force the
+      # use of a nightly release and then fail because we are attempting to analyse Swift on
+      # a non-macOS runner.
+      - name: Check out repository
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - name: Install Node.js
+        uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
+        with:
+          node-version: 20.x
+          cache: npm
+      - name: Install newer npm
+        run: npm install -g npm@11.19.1
+      - name: Install dependencies
+        run: npm ci
+      - name: Prepare test
+        id: prepare-test
+        uses: ./.github/actions/prepare-test
+        with:
+          version: ${{ matrix.version }}
+          use-all-platform-bundle: 'false'
+          setup-kotlin: 'true'
+      - name: Initialise failing analysis
+        id: init
+        uses: ./../action/init
+        continue-on-error: true
+        env:
+          CODEQL_ACTION_FORCE_NIGHTLY: true
+        with:
+          languages: swift
+          tools: ${{ steps.prepare-test.outputs.tools-url }}
+
+      - name: Check diagnostics appear on disk
+        env:
+          SARIF_PATH: '${{ runner.temp }}/codeql-action-temp-diagnostics/'
+        run: npx tsx ./pr-checks/diagnostics-without-db.ts
+    env:
+      CODEQL_ACTION_TEST_MODE: true

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 See the [releases page](https://github.com/github/codeql-action/releases) for the relevant changes to the CodeQL CLI and language packs.
 
+## [UNRELEASED]
+
+No user facing changes.
+
 ## 4.38.3 - 08 Oct 2026
 
 - _Upcoming breaking change_: CodeQL version 2.21.2 and earlier were discontinued on 24 September 2026 alongside GitHub Enterprise Server 3.17, and will be unsupported by the next minor release of the CodeQL Action. Added a deprecation warning for customers using these versions of CodeQL. [#4188](https://github.com/github/codeql-action/pull/4188)

ava.setup.mjs

@@ -1,3 +1,4 @@
 import pkg from "./package.json" with { type: "json" };
 
 globalThis.__CODEQL_ACTION_VERSION__ = pkg.version;
+globalThis.__CODEQL_ACTION_TEST_ENV__ = "unit-test";

build.mjs

@@ -78,7 +78,7 @@ const UPLOAD_LIB_SRC = "./src/upload-lib";
  *
  * The virtual module additionally re-exports `upload-lib` under the `uploadLib` namespace so that
  * external consumers can access it via the small `lib/upload-lib.js` stub emitted below.
- * 
+ *
  * A tiny stub file is emitted for each Action entrypoint, and one for `upload-lib`. Each stub
  * imports the shared bundle and calls/re-exports from the respective entry point.
  *
@@ -212,6 +212,7 @@ const context = await esbuild.context({
   target: ["node20"],
   define: {
     __CODEQL_ACTION_VERSION__: JSON.stringify(pkg.version),
+    __CODEQL_ACTION_TEST_ENV__: JSON.stringify(""),
   },
   metafile: true,
 });

eslint.config.mjs

@@ -140,6 +140,17 @@ export default [
       "no-async-foreach/no-async-foreach": "error",
       "no-sequences": "error",
       "no-shadow": "off",
+
+      // A basic check that we don't use `exportVariable` from `@actions/core`.
+      "no-restricted-syntax": [
+        "error",
+        {
+          selector: "MemberExpression[property.name='exportVariable']",
+          message:
+            "Use the `export` method of an `Env` instance or `exportEnvVar` from `environment.ts` instead.",
+        },
+      ],
+
       // This is overly restrictive with unsetting `EnvVar`s
       "@typescript-eslint/no-dynamic-delete": "off",
       "@typescript-eslint/no-shadow": "error",
@@ -157,6 +168,15 @@ export default [
       ],
     },
   },
+  {
+    files: ["src/environment.ts"],
+
+    // We allow `exportVariable` from `@actions/core` to be used in this file
+    // since it defines the wrapper around it that other modules use.
+    rules: {
+      "no-restricted-syntax": "off",
+    },
+  },
   {
     files: ["**/*.ts", "**/*.js"],
 

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "codeql",
-  "version": "4.38.3",
+  "version": "4.38.4",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "codeql",
-      "version": "4.38.3",
+      "version": "4.38.4",
       "license": "MIT",
       "workspaces": [
         "pr-checks"
@@ -58,7 +58,7 @@
         "eslint-import-resolver-typescript": "^4.4.5",
         "eslint-plugin-github": "^6.1.2",
         "eslint-plugin-import-x": "^4.17.1",
-        "eslint-plugin-jsdoc": "^64.5.4",
+        "eslint-plugin-jsdoc": "^65.0.1",
         "eslint-plugin-no-async-foreach": "^0.1.1",
         "glob": "^13.0.6",
         "globals": "^17.12.0",
@@ -5381,15 +5381,15 @@
       }
     },
     "node_modules/eslint-plugin-jsdoc": {
-      "version": "64.5.4",
-      "resolved": "https://registry.npmjs.org/eslint-plugin-jsdoc/-/eslint-plugin-jsdoc-64.5.4.tgz",
-      "integrity": "sha512-xfRhXPSSWT612muJ6XTvxuVJ8zYHv99qNgBqPVqF28aSqoy4s4XbSkrWXnYA2hl5ejC02yEpk6fqkj3BmJ6Xbg==",
+      "version": "65.0.1",
+      "resolved": "https://registry.npmjs.org/eslint-plugin-jsdoc/-/eslint-plugin-jsdoc-65.0.1.tgz",
+      "integrity": "sha512-7IvB+ZS71WCw5tGKh6f6D5k55qtXKdrGTnIpQTBKWdpyZ5IfhGHfh0i6ArWlCJ4JEtz22YRk5Bqu1MvbOlpMKQ==",
       "dev": true,
       "license": "BSD-3-Clause",
       "dependencies": {
         "@es-joy/jsdoccomment": "~0.98.0",
         "@es-joy/resolve.exports": "1.2.0",
-        "@typescript-eslint/utils": "^8.70.0",
+        "@typescript-eslint/utils": "^8.70.1",
         "are-docs-informative": "^0.1.1",
         "comment-parser": "1.4.9",
         "debug": "^4.4.3",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "codeql",
-  "version": "4.38.3",
+  "version": "4.38.4",
   "private": true,
   "description": "CodeQL action",
   "scripts": {
@@ -66,7 +66,7 @@
     "eslint-import-resolver-typescript": "^4.4.5",
     "eslint-plugin-github": "^6.1.2",
     "eslint-plugin-import-x": "^4.17.1",
-    "eslint-plugin-jsdoc": "^64.5.4",
+    "eslint-plugin-jsdoc": "^65.0.1",
     "eslint-plugin-no-async-foreach": "^0.1.1",
     "glob": "^13.0.6",
     "globals": "^17.12.0",

pr-checks/changelog/validate.test.ts

@@ -154,26 +154,6 @@ await describe("isValidChangenoteFile", async () => {
     assert.equal(isValidChangenoteFile("non-existent-file.md"), false);
   });
 
-  await it("rejects invalid filename", async () => {
-    await withTmpFile(
-      "fix-bug.md",
-      "---\ncategory: fix\n---\n- Fixed a bug\n",
-      (filePath) => {
-        assert.equal(isValidChangenoteFile(filePath), false);
-      },
-    );
-  });
-
-  await it("rejects missing frontmatter", async () => {
-    await withTmpFile(
-      "2026-01-01-fix-bug.md",
-      "- Fixed a bug\n",
-      (filePath) => {
-        assert.equal(isValidChangenoteFile(filePath), false);
-      },
-    );
-  });
-
   await it("rejects invalid Markdown", async () => {
     await withTmpFile(
       "2026-01-01-fix-bug.md",

pr-checks/changelog/validate.ts

@@ -1,5 +1,4 @@
 import * as fs from "node:fs";
-import * as path from "node:path";
 
 import { matter } from "lite-matter";
 import type { List, ListItem } from "mdast";
@@ -95,21 +94,7 @@ export function isValidChangenoteFile(filename: string): boolean {
     return false;
   }
 
-  const { data: frontmatter, content } = matter(fileData);
-
-  if (!isValidChangenoteFilename(path.basename(filename))) {
-    isValid = false;
-    console.error(
-      `${filename}: invalid filename; must match pattern YYYY-MM-DD-id.md`,
-    );
-  }
-  if (!hasValidChangenoteCategory(frontmatter)) {
-    isValid = false;
-    const categories = Object.keys(VALID_CHANGE_NOTE_CATEGORIES).join(", ");
-    console.error(
-      `${filename}: invalid category; must be one of: ${categories}`,
-    );
-  }
+  const { content } = matter(fileData);
   if (!isValidChangenoteContent(content)) {
     isValid = false;
     console.error(

pr-checks/checks/diagnostics-without-db.yml

@@ -0,0 +1,25 @@
+name: "Diagnostic export without database"
+description: "Tests that temporary diagnostics are correctly included in the failed SARIF."
+versions:
+  # Overriden by the FF below.
+  - linked
+installNode: true
+steps:
+  # We deliberately need to make this step fail before the database is initialised, but after
+  # some diagnostic has been produced. The simplest way to do that right now is to force the
+  # use of a nightly release and then fail because we are attempting to analyse Swift on
+  # a non-macOS runner.
+  - name: Initialise failing analysis
+    id: init
+    uses: ./../action/init
+    continue-on-error: true
+    env:
+      CODEQL_ACTION_FORCE_NIGHTLY: true
+    with:
+      languages: swift
+      tools: ${{ steps.prepare-test.outputs.tools-url }}
+
+  - name: Check diagnostics appear on disk
+    env:
+      SARIF_PATH: "${{ runner.temp }}/codeql-action-temp-diagnostics/"
+    run: npx tsx ./pr-checks/diagnostics-without-db.ts

pr-checks/diagnostics-without-db.ts

@@ -0,0 +1,40 @@
+import * as fs from "fs";
+import * as path from "path";
+
+import * as core from "@actions/core";
+
+import type * as diagnostics from "../src/diagnostics";
+
+const DIAGNOSTIC_ID = "codeql-action/forced-nightly-cli";
+const sarifDirectory = process.env["SARIF_PATH"];
+
+if (sarifDirectory === undefined) {
+  throw new Error("SARIF_PATH is undefined.");
+}
+
+const paths = fs.readdirSync(sarifDirectory, {
+  recursive: true,
+  encoding: "utf-8",
+});
+
+let found = false;
+for (const diagnosticPath of paths) {
+  if (path.extname(diagnosticPath) !== ".json") {
+    core.info(`Skipping ${diagnosticPath}.`);
+    continue;
+  }
+  core.info(`Found ${diagnosticPath}.`);
+
+  const contents = JSON.parse(
+    fs.readFileSync(path.resolve(sarifDirectory, diagnosticPath), "utf-8"),
+  ) as diagnostics.DiagnosticMessage;
+
+  if (contents.source.id === DIAGNOSTIC_ID) {
+    found = true;
+    break;
+  }
+}
+
+if (!found) {
+  throw new Error(`Didn't find '${DIAGNOSTIC_ID}' diagnostic.`);
+}

queries/default-setup-environment-variables.ql

@@ -23,7 +23,8 @@ predicate isSafeForDefaultSetup(string envVar) {
       "GITHUB_BASE_REF", "GITHUB_EVENT_NAME", "GITHUB_JOB", "GITHUB_RUN_ATTEMPT", "GITHUB_RUN_ID",
       "GITHUB_SHA", "GITHUB_REPOSITORY", "GITHUB_SERVER_URL", "GITHUB_TOKEN", "GITHUB_WORKFLOW",
       "GITHUB_WORKSPACE", "GOFLAGS", "ImageVersion", "JAVA_TOOL_OPTIONS", "RUNNER_ARCH",
-      "RUNNER_ENVIRONMENT", "RUNNER_NAME", "RUNNER_OS", "RUNNER_TEMP", "RUNNER_TOOL_CACHE"
+      "RUNNER_ENVIRONMENT", "RUNNER_NAME", "RUNNER_OS", "RUNNER_TEMP", "RUNNER_TOOL_CACHE",
+      "NODE_ENV"
     ]
 }
 

src/action-common.ts

@@ -1,9 +1,13 @@
+import * as fs from "fs";
+import * as os from "os";
+
 import * as core from "@actions/core";
 
 import { ActionsEnv, getActionsEnv } from "./actions-util";
 import type { ApiClient } from "./api-client";
 import { Env, ReadOnlyEnv } from "./environment";
 import type { FeatureEnablement } from "./feature-flags";
+import type { FileSystem } from "./fs";
 import { getActionsLogger, Logger } from "./logging";
 import {
   ActionName,
@@ -13,6 +17,8 @@ import {
 } from "./status-report";
 import { getEnv, getErrorMessage, wrapError } from "./util";
 
+export type { Logger } from "./logging";
+
 /** Base state that is available to an Action on startup. */
 export interface BaseState {
   /** The name of the Action. */
@@ -23,6 +29,8 @@ export interface BaseState {
   platform: NodeJS.Platform;
   /** The architecture of the host. */
   arch: NodeJS.Architecture;
+  /** The version of the operating system. */
+  osRelease: string;
 }
 
 /** Describes different state features that an Action may have. */
@@ -51,6 +59,10 @@ export interface FeatureState {
     /** Information about enabled feature flags. */
     features: FeatureEnablement;
   };
+  FS: {
+    /** The file system operations to use. */
+    fs: FileSystem;
+  };
 }
 
 /** Identifies a type of state an Action may have. */
@@ -74,7 +86,7 @@ export type ActionState<Fs extends readonly StateFeature[]> = FieldsOf<Fs>;
  * Each Action can then augment the `state` further if additional features are required.
  */
 export type ActionMain = (
-  state: ActionState<["Base", "Logger", "Env", "Actions"]>,
+  state: ActionState<["Base", "FS", "Logger", "Env", "Actions"]>,
 ) => Promise<void>;
 
 /** A specification for a CodeQL Action step. */
@@ -104,6 +116,8 @@ export async function runInActions(action: Action) {
       startedAt,
       platform: process.platform,
       arch: process.arch,
+      osRelease: os.release(),
+      fs,
       logger,
       env,
       actions: actionsEnv,

src/actions-util.ts

@@ -30,7 +30,6 @@ declare const __CODEQL_ACTION_VERSION__: string;
 export interface ActionsEnv {
   getRequiredInput: (name: string) => string;
   getOptionalInput: (name: string) => string | undefined;
-  exportVariable: (name: string, value: string) => void;
 }
 
 /**
@@ -40,7 +39,6 @@ export function getActionsEnv(): ActionsEnv {
   return {
     getRequiredInput,
     getOptionalInput,
-    exportVariable: core.exportVariable,
   };
 }
 
@@ -74,7 +72,7 @@ export const getOptionalInput = function (name: string): string | undefined {
  * directory that has been set in `CODEQL_ACTION_TEMP` by e.g. a previous step, or the
  * value of `RUNNER_TEMP` otherwise.
  */
-export function getTemporaryDirectory(env: Env = getEnv()): string {
+export function getTemporaryDirectory(env: ReadOnlyEnv = getEnv()): string {
   return (
     env.getOptional(EnvVar.TEMP) ?? env.getRequired(ActionsEnvVars.RUNNER_TEMP)
   );

src/analyze-action.ts

@@ -214,9 +214,10 @@ async function runAutobuildIfLegacyGoWorkflow(config: Config, logger: Logger) {
 
 async function run({
   startedAt,
+  env,
   logger,
   actions,
-}: ActionState<["Base", "Logger", "Actions"]>) {
+}: ActionState<["Base", "Env", "Logger", "Actions"]>) {
   // To capture errors appropriately, keep as much code within the try-catch as
   // possible, and only use safe functions outside.
 
@@ -287,7 +288,7 @@ async function run({
 
     const apiDetails = getApiDetails();
     const outputDir = actionsUtil.getRequiredInput("output");
-    core.exportVariable(EnvVar.SARIF_RESULTS_OUTPUT_DIR, outputDir);
+    env.export(EnvVar.SARIF_RESULTS_OUTPUT_DIR, outputDir);
     const threads = util.getThreadsFlag(
       actionsUtil.getOptionalInput("threads") || process.env["CODEQL_THREADS"],
       logger,
@@ -456,7 +457,7 @@ async function run({
         `expect-error input was set to true but no error was thrown.`,
       );
     }
-    core.exportVariable(EnvVar.ANALYZE_DID_COMPLETE_SUCCESSFULLY, "true");
+    env.export(EnvVar.ANALYZE_DID_COMPLETE_SUCCESSFULLY, "true");
   } catch (unwrappedError) {
     const error = util.wrapError(unwrappedError);
     if (

src/api-client.ts

@@ -17,6 +17,7 @@ import {
   ReadOnlyEnv,
   RegistryProxyVars,
   getEnv,
+  exportEnvVar,
 } from "./environment";
 import { Logger } from "./logging";
 import { getRepositoryNwo, RepositoryNwo } from "./repository";
@@ -316,7 +317,7 @@ export async function getAnalysisKey(): Promise<string> {
   const jobName = getRequiredEnvParam("GITHUB_JOB");
 
   analysisKey = `${workflowPath}:${jobName}`;
-  core.exportVariable(EnvVar.ANALYSIS_KEY, analysisKey);
+  exportEnvVar(EnvVar.ANALYSIS_KEY, analysisKey);
   return analysisKey;
 }
 

src/autobuild-action.ts

@@ -68,7 +68,11 @@ async function sendCompletedStatusReport(
   }
 }
 
-async function run({ startedAt, logger }: ActionState<["Base", "Logger"]>) {
+async function run({
+  startedAt,
+  env,
+  logger,
+}: ActionState<["Base", "Env", "Logger"]>) {
   // To capture errors appropriately, keep as much code within the try-catch as
   // possible, and only use safe functions outside.
 
@@ -135,7 +139,7 @@ async function run({ startedAt, logger }: ActionState<["Base", "Logger"]>) {
     return;
   }
 
-  core.exportVariable(EnvVar.AUTOBUILD_DID_COMPLETE_SUCCESSFULLY, "true");
+  env.export(EnvVar.AUTOBUILD_DID_COMPLETE_SUCCESSFULLY, "true");
 
   await sendCompletedStatusReport(config, logger, startedAt, languages ?? []);
 }

src/autobuild.ts

@@ -1,11 +1,9 @@
-import * as core from "@actions/core";
-
 import { getTemporaryDirectory, getWorkflowEventName } from "./actions-util";
 import { getGitHubVersion } from "./api-client";
 import { CodeQL, getCodeQL } from "./codeql";
 import * as configUtils from "./config-utils";
 import { DocUrl } from "./doc-url";
-import { ActionsEnvVars, EnvVar } from "./environment";
+import { ActionsEnvVars, EnvVar, exportEnvVar } from "./environment";
 import { Feature, featureConfig, initFeatures } from "./feature-flags";
 import { BuiltInLanguage, Language } from "./languages";
 import { Logger } from "./logging";
@@ -136,16 +134,16 @@ export async function setupCppAutobuild(codeql: CodeQL, logger: Logger) {
             : ""
         }`,
       );
-      core.exportVariable(envVar, "false");
+      exportEnvVar(envVar, "false");
     } else {
       logger.info(
         `Enabling ${featureName}. This can be disabled by setting the ${envVar} environment variable to 'false'. See ${DocUrl.DEFINE_ENV_VARIABLES} for more information.`,
       );
-      core.exportVariable(envVar, "true");
+      exportEnvVar(envVar, "true");
     }
   } else {
     logger.info(`Disabling ${featureName}.`);
-    core.exportVariable(envVar, "false");
+    exportEnvVar(envVar, "false");
   }
 }
 
@@ -165,7 +163,7 @@ export async function runAutobuild(
     await codeQL.runAutobuild(config, language);
   }
   if (language === BuiltInLanguage.go) {
-    core.exportVariable(EnvVar.DID_AUTOBUILD_GOLANG, "true");
+    exportEnvVar(EnvVar.DID_AUTOBUILD_GOLANG, "true");
   }
   logger.endGroup();
 }

src/cli/output-cache.ts

@@ -2,7 +2,7 @@ import * as fs from "fs";
 import path from "path";
 
 import { getTemporaryDirectory } from "../actions-util";
-import { Env } from "../environment";
+import { ReadOnlyEnv } from "../environment";
 import * as json from "../json";
 import { Logger } from "../logging";
 
@@ -51,7 +51,7 @@ export function resetCachedCodeQlVersion(): void {
  * Returns the path to the temporary file that backs the
  * on-disk cache of CLI responses between workflow steps.
  */
-export function getCommandCacheFilePath(env: Env): string {
+export function getCommandCacheFilePath(env: ReadOnlyEnv): string {
   return path.join(getTemporaryDirectory(env), COMMAND_CACHE_FILENAME);
 }
 

src/codeql.ts

@@ -17,7 +17,7 @@ import type { VersionInfo } from "./cli/types";
 import { CliError, wrapCliConfigurationError } from "./cli-errors";
 import { appendExtraQueryExclusions, type Config } from "./config-utils";
 import { DocUrl } from "./doc-url";
-import { EnvVar, getEnv } from "./environment";
+import { EnvVar, getEnv, exportEnvVar, Env, ReadOnlyEnv } from "./environment";
 import {
   CodeQLDefaultVersionInfo,
   Feature,
@@ -198,6 +198,7 @@ export interface CodeQL {
     sarifFile: string,
     automationDetailsId: string | undefined,
     config: Config,
+    diagnosticDir: string | undefined,
   ): Promise<void>;
   /** Get the location of an extractor for the specified language. */
   resolveExtractor(language: Language): Promise<string>;
@@ -493,8 +494,9 @@ export function createStubCodeQL(partialCodeql: Partial<CodeQL>): CodeQL {
 export async function getCodeQLForTesting(
   cmd = "codeql-for-testing",
   logger: Logger = getRunnerLogger(true),
+  env: Env = getEnv(),
 ): Promise<CodeQL> {
-  return getCodeQLForCmd(logger, cmd, false);
+  return getCodeQLForCmd(logger, cmd, false, env);
 }
 
 /**
@@ -509,13 +511,14 @@ async function getCodeQLForCmd(
   logger: Logger,
   cmd: string,
   checkVersion: boolean,
+  env: Env = getEnv(),
 ): Promise<CodeQL> {
   const codeql: CodeQL = {
     getPath() {
       return cmd;
     },
     async getVersion() {
-      const cacheFilePath = outputCache.getCommandCacheFilePath(getEnv());
+      const cacheFilePath = outputCache.getCommandCacheFilePath(env);
       let result = outputCache.getCachedCodeQlVersion(
         logger,
         cacheFilePath,
@@ -641,7 +644,7 @@ async function getCodeQLForCmd(
       }
     },
     async runAutobuild(config: Config, language: Language) {
-      applyAutobuildAzurePipelinesTimeoutFix();
+      applyAutobuildAzurePipelinesTimeoutFix(env);
 
       const autobuildCmd = path.join(
         await this.resolveExtractor(language),
@@ -651,8 +654,11 @@ async function getCodeQLForCmd(
 
       // Bump the verbosity of the autobuild command if we're in debug mode
       if (config.debugMode) {
-        process.env[EnvVar.CLI_VERBOSITY] =
-          process.env[EnvVar.CLI_VERBOSITY] || EXTRACTION_DEBUG_MODE_VERBOSITY;
+        env.set(
+          EnvVar.CLI_VERBOSITY,
+          env.getOptional(EnvVar.CLI_VERBOSITY) ??
+            EXTRACTION_DEBUG_MODE_VERBOSITY,
+        );
       }
 
       // On macOS, System Integrity Protection (SIP) typically interferes with
@@ -684,7 +690,7 @@ async function getCodeQLForCmd(
     },
     async extractUsingBuildMode(config: Config, language: Language) {
       if (config.buildMode === BuildMode.Autobuild) {
-        applyAutobuildAzurePipelinesTimeoutFix();
+        applyAutobuildAzurePipelinesTimeoutFix(env);
       }
       try {
         await runCli(cmd, [
@@ -816,7 +822,7 @@ async function getCodeQLForCmd(
         "--sarif-group-rules-by-pack",
         "--sarif-include-query-help=always",
         "--sublanguage-file-coverage",
-        ...(await getJobRunUuidSarifOptions()),
+        ...(await getJobRunUuidSarifOptions(env)),
         ...getExtraOptionsFromEnv(["database", "interpret-results"]),
       ];
       if (sarifRunPropertyFlag !== undefined) {
@@ -914,6 +920,7 @@ async function getCodeQLForCmd(
       sarifFile: string,
       automationDetailsId: string | undefined,
       config: Config,
+      diagnosticDir: string | undefined,
     ): Promise<void> {
       const args = [
         "diagnostics",
@@ -923,6 +930,9 @@ async function getCodeQLForCmd(
         `--sarif-codescanning-config=${getGeneratedCodeScanningConfigPath(
           config,
         )}`,
+        ...(diagnosticDir !== undefined
+          ? [`--diagnostic-dir=${diagnosticDir}`]
+          : []),
         ...getExtraOptionsFromEnv(["diagnostics", "export"]),
       ];
       if (automationDetailsId !== undefined) {
@@ -1036,7 +1046,7 @@ async function getCodeQLForCmd(
     );
   } else if (
     checkVersion &&
-    process.env[EnvVar.SUPPRESS_DEPRECATED_SOON_WARNING] !== "true" &&
+    env.getOptional(EnvVar.SUPPRESS_DEPRECATED_SOON_WARNING) !== "true" &&
     !(await util.codeQlVersionAtLeast(codeql, CODEQL_NEXT_MINIMUM_VERSION))
   ) {
     const result = await codeql.getVersion();
@@ -1054,7 +1064,7 @@ async function getCodeQLForCmd(
         }' by 'github/codeql-action/*@v${getActionVersion()}' in your code scanning workflow to ` +
         "continue using this version of the CodeQL Action.",
     );
-    core.exportVariable(EnvVar.SUPPRESS_DEPRECATED_SOON_WARNING, "true");
+    exportEnvVar(EnvVar.SUPPRESS_DEPRECATED_SOON_WARNING, "true");
   }
   return codeql;
 }
@@ -1256,17 +1266,20 @@ function getExtractionVerbosityArguments(
  * Without the fix, long build processes will timeout when pulling down Java packages
  * https://developercommunity.visualstudio.com/content/problem/292284/maven-hosted-agent-connection-timeout.html
  */
-function applyAutobuildAzurePipelinesTimeoutFix() {
-  const javaToolOptions = process.env["JAVA_TOOL_OPTIONS"] || "";
-  process.env["JAVA_TOOL_OPTIONS"] = [
-    ...javaToolOptions.split(/\s+/),
-    "-Dhttp.keepAlive=false",
-    "-Dmaven.wagon.http.pool=false",
-  ].join(" ");
+function applyAutobuildAzurePipelinesTimeoutFix(env: Env) {
+  const javaToolOptions = env.getOptional("JAVA_TOOL_OPTIONS") ?? "";
+  env.set(
+    "JAVA_TOOL_OPTIONS",
+    [
+      ...javaToolOptions.split(/\s+/),
+      "-Dhttp.keepAlive=false",
+      "-Dmaven.wagon.http.pool=false",
+    ].join(" "),
+  );
 }
 
-async function getJobRunUuidSarifOptions() {
-  const jobRunUuid = process.env[EnvVar.JOB_RUN_UUID];
+async function getJobRunUuidSarifOptions(env: ReadOnlyEnv) {
+  const jobRunUuid = env.getOptional(EnvVar.JOB_RUN_UUID);
 
   return jobRunUuid ? [`--sarif-run-property=jobRunUuid=${jobRunUuid}`] : [];
 }

src/config-utils.ts

@@ -2,7 +2,6 @@ import * as fs from "fs";
 import * as path from "path";
 import { performance } from "perf_hooks";
 
-import * as core from "@actions/core";
 import * as yaml from "js-yaml";
 
 import { ActionState } from "./action-common";
@@ -46,7 +45,7 @@ import {
   makeTelemetryDiagnostic,
 } from "./diagnostics";
 import { prepareDiffInformedAnalysis } from "./diff-informed-analysis-utils";
-import { EnvVar } from "./environment";
+import { EnvVar, exportEnvVar } from "./environment";
 import * as errorMessages from "./error-messages";
 import { Feature, FeatureEnablement, FeatureWithoutCLI } from "./feature-flags";
 import {
@@ -965,10 +964,10 @@ async function setCppTrapCachingEnvironmentVariables(
       );
     } else if (config.trapCaches[BuiltInLanguage.cpp]) {
       logger.info("Enabling TRAP caching for C/C++.");
-      core.exportVariable(envVar, "true");
+      exportEnvVar(envVar, "true");
     } else {
       logger.debug(`Disabling TRAP caching for C/C++.`);
-      core.exportVariable(envVar, "false");
+      exportEnvVar(envVar, "false");
     }
   }
 }

src/config/db-config.test.ts

@@ -9,8 +9,9 @@ import {
   LoggedMessage,
   makeMacro,
   RecordingLogger,
+  setupActionsVars,
 } from "../testing-utils";
-import { ConfigurationError, prettyPrintPack } from "../util";
+import { ConfigurationError, prettyPrintPack, withTmpDir } from "../util";
 
 import * as dbConfig from "./db-config";
 
@@ -562,69 +563,84 @@ test("mergeDefaultSetupAndUserConfigs - keeps other properties from user-supplie
   t.deepEqual(result, configFile);
 });
 
-test("mergeDefaultSetupAndUserConfigs - ignores, but warns about, unknown keys from Default Setup", async (t) => {
-  const logger = new RecordingLogger();
-  const configFile: dbConfig.UserConfig = {
-    "query-filters": [{ exclude: { a: "b" } }],
-    "paths-ignore": ["path"],
-  };
+test.serial(
+  "mergeDefaultSetupAndUserConfigs - ignores, but warns about, unknown keys from Default Setup",
+  async (t) => {
+    const logger = new RecordingLogger();
+    const configFile: dbConfig.UserConfig = {
+      "query-filters": [{ exclude: { a: "b" } }],
+      "paths-ignore": ["path"],
+    };
 
-  const result = dbConfig.mergeDefaultSetupAndUserConfigs(
-    logger,
-    {
-      "default-setup": {
-        borg: [],
-        org: {
-          unknown: "foo",
-          "model-packs": [],
+    await withTmpDir(async (tmpDir) => {
+      setupActionsVars(tmpDir, tmpDir);
+      const result = dbConfig.mergeDefaultSetupAndUserConfigs(
+        logger,
+        {
+          "default-setup": {
+            borg: [],
+            org: {
+              unknown: "foo",
+              "model-packs": [],
+            },
+          } as unknown as dbConfig.DefaultSetupConfig,
+          "paths-ignore": ["other-path"],
         },
-      } as unknown as dbConfig.DefaultSetupConfig,
-      "paths-ignore": ["other-path"],
-    },
-    configFile,
-  );
+        configFile,
+      );
 
-  t.deepEqual(result, {
-    ...configFile,
-    "default-setup": { org: { "model-packs": [] } },
-  });
+      t.deepEqual(result, {
+        ...configFile,
+        "default-setup": { org: { "model-packs": [] } },
+      });
 
-  const expectedUnrecognisedKeys = [
-    ".default-setup.org.unknown",
-    ".default-setup.borg",
-    ".paths-ignore",
-  ].join(", ");
-  checkExpectedLogMessages(t, logger.messages, [
-    `Unrecognised keys in Default Setup configuration: ${expectedUnrecognisedKeys}`,
-  ]);
-});
+      const expectedUnrecognisedKeys = [
+        ".default-setup.org.unknown",
+        ".default-setup.borg",
+        ".paths-ignore",
+      ].join(", ");
+      checkExpectedLogMessages(t, logger.messages, [
+        `Unrecognised keys in Default Setup configuration: ${expectedUnrecognisedKeys}`,
+      ]);
+    });
+  },
+);
 
-test("mergeDefaultSetupAndUserConfigs - warns about invalid keys from Default Setup", async (t) => {
-  const logger = new RecordingLogger();
-  const configFile: dbConfig.UserConfig = {};
+test.serial(
+  "mergeDefaultSetupAndUserConfigs - warns about invalid keys from Default Setup",
+  async (t) => {
+    const logger = new RecordingLogger();
+    const configFile: dbConfig.UserConfig = {};
 
-  const result = dbConfig.mergeDefaultSetupAndUserConfigs(
-    logger,
-    {
-      "default-setup": {
-        org: {
-          "model-packs": [123],
+    await withTmpDir(async (tmpDir) => {
+      setupActionsVars(tmpDir, tmpDir);
+
+      const result = dbConfig.mergeDefaultSetupAndUserConfigs(
+        logger,
+        {
+          "default-setup": {
+            org: {
+              "model-packs": [123],
+            },
+          } as unknown as dbConfig.DefaultSetupConfig,
         },
-      } as unknown as dbConfig.DefaultSetupConfig,
-    },
-    configFile,
-  );
+        configFile,
+      );
 
-  t.deepEqual(result, {
-    ...configFile,
-    "default-setup": { org: { "model-packs": [123] } },
-  });
+      t.deepEqual(result, {
+        ...configFile,
+        "default-setup": { org: { "model-packs": [123] } },
+      });
 
-  const expectedInvalidKeys = [".default-setup.org.model-packs[0]"].join(", ");
-  checkExpectedLogMessages(t, logger.messages, [
-    `Invalid keys in Default Setup configuration: ${expectedInvalidKeys}`,
-  ]);
-});
+      const expectedInvalidKeys = [".default-setup.org.model-packs[0]"].join(
+        ", ",
+      );
+      checkExpectedLogMessages(t, logger.messages, [
+        `Invalid keys in Default Setup configuration: ${expectedInvalidKeys}`,
+      ]);
+    });
+  },
+);
 
 /** Parses `contents` as a configuration without validating it. */
 function parseUnvalidatedConfig(contents: string): dbConfig.UserConfig {

src/debug-artifacts.ts

@@ -11,7 +11,7 @@ import { dbIsFinalized } from "./analyze";
 import { scanArtifactsForTokens } from "./artifact-scanner";
 import { type CodeQL } from "./codeql";
 import { Config } from "./config-utils";
-import { EnvVar } from "./environment";
+import { EnvVar, exportEnvVar } from "./environment";
 import * as json from "./json";
 import { Language } from "./languages";
 import { Logger, withGroup } from "./logging";
@@ -330,7 +330,7 @@ export async function uploadArtifacts(
   // some issues early.
   if (isInTestMode()) {
     await scanArtifactsForTokens(toUpload, logger);
-    core.exportVariable("CODEQL_ACTION_ARTIFACT_SCAN_FINISHED", "true");
+    exportEnvVar("CODEQL_ACTION_ARTIFACT_SCAN_FINISHED", "true");
   }
 
   const suffix = getArtifactSuffix(getOptionalInput("matrix"));

src/diagnostics.test.ts

@@ -0,0 +1,123 @@
+import * as fs from "fs";
+import path from "path";
+
+import test from "ava";
+import * as sinon from "sinon";
+
+import * as diagnostics from "./diagnostics";
+import type { FileSystem } from "./fs";
+import { BuiltInLanguage } from "./languages";
+import {
+  checkExpectedLogMessages,
+  createTestConfig,
+  initAllState,
+  RecordingLogger,
+  setupTests,
+} from "./testing-utils";
+
+setupTests(test);
+
+type TestFS = FileSystem<
+  "existsSync" | "mkdirSync" | "writeFileSync" | "readFileSync" | "renameSync"
+>;
+
+function makeStubFS() {
+  // The functions in `fs` cannot be stubbed. Create a new, minimal object
+  // that we can stub.
+  const stubbedFS: TestFS = {
+    existsSync: fs.existsSync,
+    mkdirSync: fs.mkdirSync,
+    writeFileSync: fs.writeFileSync,
+    readFileSync: fs.readFileSync,
+    renameSync: fs.renameSync,
+  };
+
+  const existsSync = sinon.stub(stubbedFS, "existsSync");
+  const mkdirSync = sinon.stub(stubbedFS, "mkdirSync");
+  const writeFileSync = sinon.stub(stubbedFS, "writeFileSync");
+  const readFileSync = sinon.stub(stubbedFS, "readFileSync");
+  const renameSync = sinon.stub(stubbedFS, "renameSync");
+
+  return {
+    stubbedFS,
+    existsSync,
+    mkdirSync,
+    writeFileSync,
+    readFileSync,
+    renameSync,
+  };
+}
+
+const id = "codeql-action/test-diagnostic";
+const name = "Test title";
+
+test("makeDiagnostic - adds expected properties", (t) => {
+  const diagnostic = diagnostics.makeDiagnostic(id, name, {});
+
+  t.truthy(diagnostic.timestamp);
+  t.is(diagnostic.source.id, id);
+  t.is(diagnostic.source.name, name);
+});
+
+test("addDiagnostic writes temporary diagnostics and flushDiagnostics moves them", (t) => {
+  const logger = new RecordingLogger();
+  const { stubbedFS, existsSync, mkdirSync, writeFileSync, renameSync } =
+    makeStubFS();
+
+  let databasePath: fs.PathLike | undefined;
+  existsSync.callsFake((p) => {
+    databasePath = p;
+    return false;
+  });
+
+  const diagnostic = diagnostics.makeDiagnostic(id, name, {});
+  t.notThrows(() => {
+    diagnostics.addDiagnostic(
+      createTestConfig({ tempDir: path.resolve("/temp/") }),
+      BuiltInLanguage.actions,
+      diagnostic,
+      logger,
+      stubbedFS as FileSystem,
+    );
+    diagnostics.flushDiagnostics(
+      initAllState({ logger, fs: stubbedFS as FileSystem }),
+      createTestConfig({
+        tempDir: path.resolve("/temp/"),
+        dbLocation: path.resolve("/test/database/"),
+      }),
+    );
+  });
+
+  t.is(existsSync.callCount, 1);
+  t.is(mkdirSync.callCount, 2);
+  t.is(writeFileSync.callCount, 1);
+  t.is(writeFileSync.args[0].length, 2);
+  t.is(writeFileSync.args[0][1], JSON.stringify(diagnostic));
+
+  // flushDiagnostics
+  t.is(renameSync.callCount, 1);
+  t.is(renameSync.args[0].length, 2);
+
+  const sourcePath = renameSync.args[0][0].toString();
+  const expectedSourcePathPrefix = path.resolve(
+    "/temp/codeql-action-temp-diagnostics/actions/diagnostic/codeql-action/",
+  );
+  t.true(
+    sourcePath.startsWith(expectedSourcePathPrefix),
+    `'${sourcePath}' does not start with '${expectedSourcePathPrefix}`,
+  );
+
+  const destPath = renameSync.args[0][1].toString();
+  const expectedDestPathPrefix = path.resolve(
+    "/test/database/actions/diagnostic/codeql-action/",
+  );
+  t.true(
+    destPath.startsWith(expectedDestPathPrefix),
+    `'${destPath}' does not start with '${expectedDestPathPrefix}`,
+  );
+
+  checkExpectedLogMessages(t, logger.messages, [
+    `but the database at ${databasePath} does not exist yet`,
+    "Moving 1 diagnostic(s) to their respective databases.",
+  ]);
+});

src/diagnostics.ts

@@ -1,10 +1,13 @@
-import { existsSync, mkdirSync, writeFileSync } from "fs";
+import * as nodefs from "fs";
 import path from "path";
 
+import type { ActionState } from "./action-common";
+import { getTemporaryDirectory } from "./actions-util";
 import type { Config } from "./config-utils";
+import type { FileSystem } from "./fs";
 import { Language } from "./languages";
-import { getActionsLogger } from "./logging";
-import { getCodeQLDatabasePath } from "./util";
+import { getActionsLogger, type Logger } from "./logging";
+import { getCodeQLDatabasePath, getErrorMessage } from "./util";
 
 /**
  * Known tags for diagnostics. There is currently only "internal-error",
@@ -84,22 +87,16 @@ export type DiagnosticMessage = DiagnosticMessageOptions & {
   source: DiagnosticSource;
 };
 
-/** Represents a diagnostic message that has not yet been written to the database. */
-interface UnwrittenDiagnostic {
-  /** The diagnostic message that has not yet been written. */
-  diagnostic: DiagnosticMessage;
-  /** The language the diagnostic is for. */
-  language: Language;
+/** Represents a diagnostic message that has not yet been saved to the database. */
+interface TemporaryDiagnostic {
+  /** The path to which the diagnostic has temporarily been written to. */
+  path: string;
+  /** The language the diagnostic is for, if any. */
+  language?: Language;
 }
 
-/** A list of diagnostics which have not yet been written to disk. */
-let unwrittenDiagnostics: UnwrittenDiagnostic[] = [];
-
-/**
- * A list of diagnostics which have not yet been written to disk,
- * and where the language does not matter.
- */
-let unwrittenDefaultLanguageDiagnostics: DiagnosticMessage[] = [];
+/** A list of diagnostics which have not yet been saved to the database. */
+let temporaryDiagnostics: TemporaryDiagnostic[] = [];
 
 /**
  * Counter used to generate a unique suffix for each diagnostic filename, so that
@@ -128,6 +125,29 @@ export function makeDiagnostic(
   };
 }
 
+/**
+ * Gets a path relative to {@link tmpDir} where diagnostics for {@link language}
+ * can temporarily be stored at before the database is initialised. If {@link language}
+ * is `undefined`, then the common base path for all languages relative to {@link tmpDir}
+ * is returned.
+ */
+export function getTempDiagnosticPath(tmpDir: string, language?: Language) {
+  const root = path.join(tmpDir, "codeql-action-temp-diagnostics");
+  return getDiagnosticsPath(root, language);
+}
+
+/**
+ * Gets a path relative to {@link basePath} where diagnostics for {@link language}
+ * should be stored at. If {@link language} is `undefined`, then {@link baseBath}
+ * is returned instead.
+ */
+export function getDiagnosticsPath(basePath: string, language?: Language) {
+  if (language !== undefined) {
+    return path.resolve(basePath, language, "diagnostic", "codeql-action");
+  }
+  return basePath;
+}
+
 /**
  * Adds the given diagnostic to the database. If the database does not yet exist,
  * the diagnostic will be written to it once it has been created.
@@ -140,22 +160,32 @@ export function addDiagnostic(
   config: Config,
   language: Language,
   diagnostic: DiagnosticMessage,
+  logger: Logger = getActionsLogger(),
+  fs: FileSystem = nodefs,
 ) {
-  const logger = getActionsLogger();
   const databasePath = language
     ? getCodeQLDatabasePath(config, language)
     : config.dbLocation;
 
   // Check that the database exists before writing to it. If the database does not yet exist,
   // store the diagnostic in memory and write it later.
-  if (existsSync(databasePath)) {
-    writeDiagnostic(config, language, diagnostic);
+  if (fs.existsSync(databasePath)) {
+    writeDiagnostic({ logger, fs }, config, language, diagnostic);
   } else {
     logger.debug(
       `Writing a diagnostic for ${language}, but the database at ${databasePath} does not exist yet.`,
     );
 
-    unwrittenDiagnostics.push({ diagnostic, language });
+    // Write the diagnostic to a temporary location.
+    const tempDiagnosticsPath = getTempDiagnosticPath(config.tempDir, language);
+    const diagnosticPath = writeDiagnosticFile(
+      fs,
+      tempDiagnosticsPath,
+      diagnostic,
+    );
+
+    // Track the temporary file.
+    temporaryDiagnostics.push({ path: diagnosticPath, language });
   }
 }
 
@@ -163,6 +193,7 @@ export function addDiagnostic(
 export function addNoLanguageDiagnostic(
   config: Config | undefined,
   diagnostic: DiagnosticMessage,
+  fs: FileSystem = nodefs,
 ) {
   if (config !== undefined) {
     addDiagnostic(
@@ -173,10 +204,56 @@ export function addNoLanguageDiagnostic(
       diagnostic,
     );
   } else {
-    unwrittenDefaultLanguageDiagnostics.push(diagnostic);
+    const tempDiagnosticsPath = getTempDiagnosticPath(getTemporaryDirectory());
+    const diagnosticPath = writeDiagnosticFile(
+      fs,
+      tempDiagnosticsPath,
+      diagnostic,
+    );
+
+    // Track the temporary file.
+    temporaryDiagnostics.push({ path: diagnosticPath });
   }
 }
 
+/**
+ * Writes {@link diagnostic} to a file in {@link diagnosticsPath}.
+ */
+function writeDiagnosticFile(
+  fs: FileSystem<"mkdirSync" | "writeFileSync">,
+  diagnosticsPath: string,
+  diagnostic: DiagnosticMessage,
+): string {
+  // Create the directory if it doesn't exist yet.
+  fs.mkdirSync(diagnosticsPath, { recursive: true });
+
+  // Include a monotonically increasing suffix to avoid filename collisions
+  // between diagnostics produced within the same millisecond.
+  const uniqueSuffix = (diagnosticCounter++).toString();
+  // We should only need to remove colons, but to be defensive, only allow a restricted set of
+  // characters.
+  const sanitizedTimestamp = diagnostic.timestamp.replace(
+    /[^a-zA-Z0-9.-]/g,
+    "",
+  );
+  const jsonPath = path.resolve(
+    diagnosticsPath,
+    `codeql-action-${sanitizedTimestamp}-${uniqueSuffix}.json`,
+  );
+
+  fs.writeFileSync(jsonPath, JSON.stringify(diagnostic));
+
+  return jsonPath;
+}
+
+/** Gets the path where diagnostics for {@link language} should be stored in the database. */
+export function getDatabaseDiagnosticsPath(
+  config: Config,
+  language: Language | undefined,
+) {
+  return getDiagnosticsPath(config.dbLocation, language);
+}
+
 /**
  * Writes the given diagnostic to the database.
  *
@@ -185,78 +262,74 @@ export function addNoLanguageDiagnostic(
  * @param diagnostic The diagnostic message to add to the database.
  */
 function writeDiagnostic(
+  action: ActionState<["Logger", "FS"]>,
   config: Config,
   language: Language | undefined,
   diagnostic: DiagnosticMessage,
 ) {
-  const logger = getActionsLogger();
-  const databasePath = language
-    ? getCodeQLDatabasePath(config, language)
-    : config.dbLocation;
-  const diagnosticsPath = path.resolve(
-    databasePath,
-    "diagnostic",
-    "codeql-action",
-  );
+  const diagnosticsPath = getDatabaseDiagnosticsPath(config, language);
 
   try {
-    // Create the directory if it doesn't exist yet.
-    mkdirSync(diagnosticsPath, { recursive: true });
-
-    // Include a monotonically increasing suffix to avoid filename collisions
-    // between diagnostics produced within the same millisecond.
-    const uniqueSuffix = (diagnosticCounter++).toString();
-    // We should only need to remove colons, but to be defensive, only allow a restricted set of
-    // characters.
-    const sanitizedTimestamp = diagnostic.timestamp.replace(
-      /[^a-zA-Z0-9.-]/g,
-      "",
-    );
-    const jsonPath = path.resolve(
-      diagnosticsPath,
-      `codeql-action-${sanitizedTimestamp}-${uniqueSuffix}.json`,
-    );
-
-    writeFileSync(jsonPath, JSON.stringify(diagnostic));
+    writeDiagnosticFile(action.fs, diagnosticsPath, diagnostic);
   } catch (err) {
-    logger.warning(`Unable to write diagnostic message to database: ${err}`);
-    logger.debug(JSON.stringify(diagnostic));
+    action.logger.warning(
+      `Unable to write diagnostic message to database: ${err}`,
+    );
+    action.logger.debug(JSON.stringify(diagnostic));
   }
 }
 
-/** Report if there are unwritten diagnostics and write them to the log. */
-export function logUnwrittenDiagnostics() {
-  const logger = getActionsLogger();
-  const num = unwrittenDiagnostics.length;
+/** Report if there are temporary diagnostics and write them to the log. */
+export function logTemporaryDiagnostics(action: ActionState<["Logger", "FS"]>) {
+  const num = temporaryDiagnostics.length;
+
   if (num > 0) {
-    logger.warning(
+    action.logger.warning(
       `${num} diagnostic(s) could not be written to the database and will not appear on the Tool Status Page.`,
     );
 
-    for (const unwritten of unwrittenDiagnostics) {
-      logger.debug(JSON.stringify(unwritten.diagnostic));
+    for (const temporary of temporaryDiagnostics) {
+      action.logger.debug(action.fs.readFileSync(temporary.path, "utf-8"));
     }
   }
 }
 
-/** Writes all unwritten diagnostics to disk. */
-export function flushDiagnostics(config: Config) {
-  const logger = getActionsLogger();
+/** Relocates all temporary diagnostics to the respective databases. */
+export function flushDiagnostics(
+  action: ActionState<["Logger", "FS"]>,
+  config: Config,
+) {
+  const diagnosticsCount = temporaryDiagnostics.length;
+  action.logger.debug(
+    `Moving ${diagnosticsCount} diagnostic(s) to their respective databases.`,
+  );
 
-  const diagnosticsCount =
-    unwrittenDiagnostics.length + unwrittenDefaultLanguageDiagnostics.length;
-  logger.debug(`Writing ${diagnosticsCount} diagnostic(s) to database.`);
+  const failedFlushDiagnostics: TemporaryDiagnostic[] = [];
+  for (const temporary of temporaryDiagnostics) {
+    // If `temporary.language` is `undefined`, then we didn't have a `config` at the time that
+    // `addNoLanguageDiagnostic` was called. In that case, we arbitrarily choose the first
+    // configured language here like we would have done in `addNoLanguageDiagnostic`.
+    const directory = getDatabaseDiagnosticsPath(
+      config,
+      temporary.language ?? config.languages[0],
+    );
+    const filename = path.basename(temporary.path);
+    const destination = path.join(directory, filename);
 
-  for (const unwritten of unwrittenDiagnostics) {
-    writeDiagnostic(config, unwritten.language, unwritten.diagnostic);
-  }
-  for (const unwritten of unwrittenDefaultLanguageDiagnostics) {
-    addNoLanguageDiagnostic(config, unwritten);
+    try {
+      action.fs.mkdirSync(directory, { recursive: true });
+      action.fs.renameSync(temporary.path, destination);
+    } catch (err) {
+      action.logger.warning(
+        `Failed to rename '${temporary.path}' to '${destination}': ${getErrorMessage(err)}`,
+      );
+
+      failedFlushDiagnostics.push(temporary);
+    }
   }
 
-  // Reset the unwritten diagnostics arrays.
-  unwrittenDiagnostics = [];
-  unwrittenDefaultLanguageDiagnostics = [];
+  // Reset the temporary diagnostics arrays.
+  temporaryDiagnostics = failedFlushDiagnostics;
 }
 
 /**

src/environment.test.ts

@@ -0,0 +1,12 @@
+import test from "ava";
+
+import { Env, ReadOnlyEnv } from "./environment";
+import { getTestEnv, setupTests } from "./testing-utils";
+
+setupTests(test);
+
+test("isTestingEnv() is true", (t) => {
+  t.true(new ReadOnlyEnv(process.env).isTestingEnv());
+  t.true(new Env(process.env).isTestingEnv());
+  t.true(getTestEnv().isTestingEnv());
+});

src/environment.ts

@@ -1,3 +1,10 @@
+import * as core from "@actions/core";
+
+/**
+ * This constant is set in `ava.setup.mjs` for tests.
+ */
+declare const __CODEQL_ACTION_TEST_ENV__: string | undefined;
+
 /**
  * Environment variables used by Default Setup to communicate the private registry proxy configuration.
  */
@@ -211,8 +218,20 @@ export enum ActionsEnvVars {
   RUNNER_TOOL_CACHE = "RUNNER_TOOL_CACHE",
 }
 
+/** Environment variables which are not specific to CodeQL. */
+export enum SystemEnvVar {
+  /**
+   * Used by Node and related tools to indicate what kind of environment we are running in.
+   */
+  NODE_ENV = "NODE_ENV",
+}
+
 /** A type representing all known environment variables. */
-export type KnownEnvVar = EnvVar | ActionsEnvVars | RegistryProxyVars;
+export type KnownEnvVar =
+  | EnvVar
+  | ActionsEnvVars
+  | RegistryProxyVars
+  | SystemEnvVar;
 
 /**
  * Gets an environment variable, but throws an error if it is not set.
@@ -289,6 +308,26 @@ export class ReadOnlyEnv<T extends string | undefined = string | undefined> {
   public entries(): Array<[string, T]> {
     return Object.entries(this.vars);
   }
+
+  /**
+   * Gets a value indicating whether we should skip uploads of
+   * all kinds (SARIF results, status reports, DBs, ...).
+   *
+   * This is not guaranteed to be set in all test environments.
+   */
+  public isSkippingUploadsInTests(): boolean {
+    return this.getOptional(EnvVar.TEST_MODE) === "true";
+  }
+
+  /**
+   * Gets a value indicative of whether we are in a testing environment
+   * by testing whether the value of the `NODE_ENV` variable is "test".
+   * This is expected to be the case if e.g. `ava` is running the tests
+   * or if this instance was constructed by `getTestEnv`.
+   */
+  public isTestingEnv(): boolean {
+    return __CODEQL_ACTION_TEST_ENV__ === "unit-test";
+  }
 }
 
 /**
@@ -307,6 +346,26 @@ export class Env<
     this.changed = true;
   }
 
+  /**
+   * Wrapper around `core.exportVariable` which does not call `core.exportVariable`
+   * when running unit tests. This is important, because otherwise `core.exportVariable`
+   * sets environment variables for other steps in a workflow when we run unit tests in CI.
+   *
+   * @param name The name of the environment variable to set and export.
+   * @param val The value to set and export for the environment variable.
+   */
+  public export(name: string, val: T): void {
+    // Setting the environment variable for this instance is always OK, including
+    // in tests, since we use fresh `Env` instances whenever needed. This allows
+    // tests to pass that rely on that part of the `core.exportVariable` behaviour.
+    this.set(name, val);
+
+    // Call `core.exportVariable` whenever we are not in a test environment.
+    if (!this.isTestingEnv()) {
+      core.exportVariable(name, val);
+    }
+  }
+
   /** Gets a value indicating whether `set` was called at least once. */
   public hasChanged(): boolean {
     return this.changed;
@@ -317,3 +376,34 @@ export class Env<
 export function getEnv(env: NodeJS.ProcessEnv = process.env): Env {
   return new Env(env);
 }
+
+/**
+ * Returns whether we are in test mode. This is used by CodeQL Action PR checks.
+ *
+ * In test mode, we skip several uploads (SARIF results, status reports, DBs, ...).
+ *
+ * @deprecated
+ *  The purpose of this function is ambiguous. Use `isSkippingUploadsInTests` on
+ *  a `ReadOnlyEnv` instance instead for equivalent behaviour. Use `isTestingEnv`
+ *  to determine if we are running in a unit test.
+ */
+export function isInTestMode(): boolean {
+  return getEnv().isSkippingUploadsInTests();
+}
+
+/**
+ * Wrapper around `core.exportVariable` which does not call `core.exportVariable`
+ * when running unit tests. This is important, because otherwise `core.exportVariable`
+ * sets environment variables for other steps in a workflow when we run unit tests in CI.
+ *
+ * @deprecated Use `export` on an `Env` instance instead.
+ */
+export function exportEnvVar(name: string, val: any): void {
+  const env = getEnv();
+
+  if (typeof val === "string") {
+    env.export(name, val);
+  } else {
+    env.export(name, JSON.stringify(val));
+  }
+}

src/feature-flags.ts

@@ -170,6 +170,8 @@ export enum Feature {
    */
   PerLanguageBundles = "per_language_bundles_v2",
   QaTelemetryEnabled = "qa_telemetry_enabled",
+  /** Whether we should fail early if we detect that traced Swift analysis is unsupported. */
+  SwiftSkipUnsupportedTracedAnalysis = "swift_skip_unsupported_traced_analysis",
   /** Routes (some) API requests through the registry proxy. */
   ProxyApiRequests = "proxy_api_requests",
   /** Note that this currently only disables baseline file coverage information. */
@@ -466,6 +468,11 @@ export const featureConfig = {
     envVar: "CODEQL_ACTION_START_PROXY_USE_FEATURES_RELEASE",
     minimumVersion: undefined,
   },
+  [Feature.SwiftSkipUnsupportedTracedAnalysis]: {
+    defaultValue: false,
+    envVar: "CODEQL_ACTION_SWIFT_SKIP_UNSUPPORTED_TRACED_ANALYSIS",
+    minimumVersion: undefined,
+  },
   [Feature.ToolsRepositoryProperty]: {
     defaultValue: false,
     envVar: "CODEQL_ACTION_TOOLS_REPOSITORY_PROPERTY",

src/fs.ts

@@ -0,0 +1,35 @@
+/**
+ * This module exports a `FileSystem` type which corresponds to the interface of the "fs" module.
+ *
+ * Functions which are parameterised over this type can then be passed a different implementation in tests:
+ *
+ * ```typescript
+ * import * as nodefs from "fs";
+ *
+ * function foo(fs: FileSystem = nodefs) {
+ *   // Uses the real "fs" module by default, but can be given a different implementation.
+ * }
+ * ```
+ *
+ * The type can also be constrained to a subset of available operations. For example, in the following
+ * case we have a function that only needs `statSync`:
+ *
+ * ```
+ * function bar(fs: FileSystem<"statSync"> = nodefs) {
+ *   // This function can only use `statSync`.
+ * }
+ * ```
+ *
+ * This is useful to define a clearer interface for what the function does and also only requires stubbing
+ * of the relevant functions.
+ */
+
+import * as fs from "fs";
+
+/** Represents the names of operations exported from "fs". */
+export type FileOperation = keyof typeof fs;
+
+/** Represents the type of "fs", optionally filtered down to just `Ops`. */
+export type FileSystem<Ops extends FileOperation = keyof typeof fs> = {
+  [Key in Ops]: (typeof fs)[Key];
+};

src/init-action-post-helper.ts

@@ -18,6 +18,7 @@ import {
   sanitizeArtifactName,
 } from "./debug-artifacts";
 import * as dependencyCaching from "./dependency-caching";
+import { getTempDiagnosticPath } from "./diagnostics";
 import { EnvVar, ReadOnlyEnv } from "./environment";
 import { Feature, FeatureEnablement } from "./feature-flags";
 import { Logger } from "./logging";
@@ -178,7 +179,19 @@ async function generateFailedSarif(
     databasePath === undefined ||
     !(await features.getValue(Feature.ExportDiagnosticsEnabled, codeql))
   ) {
-    await codeql.diagnosticsExport(sarifFile, category, config);
+    // If we don't have a database path, then we may have diagnostics that were written to a
+    // temporary location. Get the path that they would have been written to and check whether
+    // it exists. If so, pass it on to the CLI. The CLI will not complain if we give it a
+    // path that doesn't exist, so we are just being extra defensive here.
+    let diagnosticDir: string | undefined = getTempDiagnosticPath(
+      config.tempDir,
+    );
+
+    if (!fs.existsSync(diagnosticDir)) {
+      diagnosticDir = undefined;
+    }
+
+    await codeql.diagnosticsExport(sarifFile, category, config, diagnosticDir);
   } else {
     // We call 'database export-diagnostics' to find any per-database diagnostics.
     await codeql.databaseExportDiagnostics(databasePath, sarifFile, category);

src/init-action-post.ts

@@ -21,7 +21,7 @@ import {
   DependencyCachingUsageReport,
   getDependencyCacheUsage,
 } from "./dependency-caching";
-import { EnvVar, getEnv } from "./environment";
+import { EnvVar, getEnv, exportEnvVar } from "./environment";
 import { initFeatures } from "./feature-flags";
 import * as gitUtils from "./git-utils";
 import * as initActionPostHelper from "./init-action-post-helper";
@@ -166,7 +166,7 @@ function getFinalJobStatus(config: Config | undefined): JobStatus {
   let jobStatus: JobStatus;
 
   if (process.env[EnvVar.ANALYZE_DID_COMPLETE_SUCCESSFULLY] === "true") {
-    core.exportVariable(EnvVar.JOB_STATUS, JobStatus.SuccessStatus);
+    exportEnvVar(EnvVar.JOB_STATUS, JobStatus.SuccessStatus);
     jobStatus = JobStatus.SuccessStatus;
   } else if (config !== undefined) {
     // - We have computed a CodeQL config
@@ -191,7 +191,7 @@ function getFinalJobStatus(config: Config | undefined): JobStatus {
 
   // This shouldn't be necessary, but in the odd case that we run more than one
   // `init` post step, ensure the job status is consistent between them.
-  core.exportVariable(EnvVar.JOB_STATUS, jobStatus);
+  exportEnvVar(EnvVar.JOB_STATUS, jobStatus);
   return jobStatus;
 }
 

src/init-action.ts

@@ -35,7 +35,7 @@ import {
   addDiagnostic,
   addNoLanguageDiagnostic,
   flushDiagnostics,
-  logUnwrittenDiagnostics,
+  logTemporaryDiagnostics,
   makeDiagnostic,
   makeTelemetryDiagnostic,
 } from "./diagnostics";
@@ -56,6 +56,7 @@ import {
   runDatabaseInitCluster,
 } from "./init";
 import { JavaEnvVars, BuiltInLanguage } from "./languages";
+import { isSwiftCompatible } from "./languages/swift";
 import { Logger, withGroupAsync } from "./logging";
 import {
   downloadOverlayBaseDatabaseFromCache,
@@ -93,7 +94,6 @@ import {
   checkActionVersion,
   getErrorMessage,
   BuildMode,
-  getOptionalEnvVar,
 } from "./util";
 import { checkWorkflow } from "./workflow";
 
@@ -200,7 +200,7 @@ async function sendCompletedStatusReport(
 }
 
 async function run(
-  actionState: ActionState<["Base", "Logger", "Env", "Actions"]>,
+  actionState: ActionState<["Base", "Logger", "Env", "Actions", "FS"]>,
 ) {
   // To capture errors appropriately, keep as much code within the try-catch as
   // possible, and only use safe functions outside.
@@ -253,7 +253,7 @@ async function run(
     );
     const repositoryProperties = repositoryPropertiesResult.orElse({});
 
-    core.exportVariable(EnvVar.INIT_ACTION_HAS_RUN, "true");
+    actionState.env.export(EnvVar.INIT_ACTION_HAS_RUN, "true");
 
     // path.resolve() respects the intended semantics of source-root. If
     // source-root is relative, it is relative to the GITHUB_WORKSPACE. If
@@ -369,7 +369,7 @@ async function run(
         );
       }
       if (semver.lt(actualVer, publicPreview)) {
-        core.exportVariable(EnvVar.EXPERIMENTAL_FEATURES, "true");
+        actionState.env.export(EnvVar.EXPERIMENTAL_FEATURES, "true");
         logger.info("Experimental Rust analysis enabled");
       }
     }
@@ -418,14 +418,7 @@ async function run(
       logger,
     });
 
-    if (
-      config.languages.includes(BuiltInLanguage.swift) &&
-      process.platform !== "darwin"
-    ) {
-      throw new ConfigurationError(
-        `Swift analysis is only supported on macOS runner images. Please migrate to a macOS runner.`,
-      );
-    }
+    await isSwiftCompatible(actionStateWithFeatures, config, codeql);
 
     if (repositoryPropertiesResult.isFailure()) {
       addNoLanguageDiagnostic(
@@ -472,6 +465,7 @@ async function run(
     if (statusReportBase !== undefined) {
       await sendStatusReport(statusReportBase);
     }
+    logTemporaryDiagnostics(actionState);
     return;
   }
 
@@ -517,9 +511,9 @@ async function run(
     }
 
     // Forward Go flags
-    const goFlags = process.env["GOFLAGS"];
+    const goFlags = actionState.env.getOptional("GOFLAGS");
     if (goFlags) {
-      core.exportVariable("GOFLAGS", goFlags);
+      actionState.env.export("GOFLAGS", goFlags);
       core.warning(
         "Passing the GOFLAGS env parameter to the init action is deprecated. Please move this to the analyze action.",
       );
@@ -565,7 +559,7 @@ async function run(
 
             // Store the original location of our wrapper script somewhere where we can
             // later retrieve it from and cross-check that it hasn't been changed.
-            core.exportVariable(EnvVar.GO_BINARY_LOCATION, goWrapperPath);
+            actionState.env.export(EnvVar.GO_BINARY_LOCATION, goWrapperPath);
           } catch (e) {
             logger.warning(
               `Analyzing Go on Linux, but failed to install wrapper script. Tracing custom builds may fail: ${e}`,
@@ -574,7 +568,7 @@ async function run(
         } else {
           // Store the location of the original Go binary, so we can check that no setup tasks were performed after the
           // `init` Action ran.
-          core.exportVariable(EnvVar.GO_BINARY_LOCATION, goBinaryPath);
+          actionState.env.export(EnvVar.GO_BINARY_LOCATION, goBinaryPath);
         }
       } catch (e) {
         logger.warning(
@@ -609,12 +603,12 @@ async function run(
     // threads it would ask extractors to use. See help text for the "--ram" and "--threads"
     // options at https://codeql.github.com/docs/codeql-cli/manual/database-trace-command/
     // for details.
-    core.exportVariable(
+    actionState.env.export(
       "CODEQL_RAM",
       process.env["CODEQL_RAM"] ||
         getCodeQLMemoryLimit(getOptionalInput("ram"), logger).toString(),
     );
-    core.exportVariable(
+    actionState.env.export(
       "CODEQL_THREADS",
       process.env["CODEQL_THREADS"] ||
         getThreadsFlagValue(getOptionalInput("threads"), logger).toString(),
@@ -622,12 +616,15 @@ async function run(
 
     // Disable Kotlin extractor if feature flag set
     if (await features.getValue(Feature.DisableKotlinAnalysisEnabled)) {
-      core.exportVariable("CODEQL_EXTRACTOR_JAVA_AGENT_DISABLE_KOTLIN", "true");
+      actionState.env.export(
+        "CODEQL_EXTRACTOR_JAVA_AGENT_DISABLE_KOTLIN",
+        "true",
+      );
     }
 
     // Emergency override to force the CodeQL CLI back to the JGit-based Git backend.
     if (await features.getValue(Feature.ForceJGit)) {
-      core.exportVariable("CODEQL_GIT_BACKEND", "jgit");
+      actionState.env.export("CODEQL_GIT_BACKEND", "jgit");
     }
 
     const kotlinLimitVar =
@@ -636,7 +633,7 @@ async function run(
       (await codeQlVersionAtLeast(codeql, "2.20.3")) &&
       !(await codeQlVersionAtLeast(codeql, "2.20.4"))
     ) {
-      core.exportVariable(kotlinLimitVar, "2.1.20");
+      actionState.env.export(kotlinLimitVar, "2.1.20");
     }
 
     // Restore dependency cache(s), if they exist.
@@ -685,7 +682,7 @@ async function run(
       config.buildMode === BuildMode.None &&
       config.languages.includes(BuiltInLanguage.java)
     ) {
-      core.exportVariable(
+      actionState.env.export(
         EnvVar.JAVA_EXTRACTOR_MINIMIZE_DEPENDENCY_JARS,
         "true",
       );
@@ -743,7 +740,7 @@ async function run(
     const tracerConfig = await getCombinedTracerConfig(logger, codeql, config);
     if (tracerConfig !== undefined) {
       for (const [key, value] of Object.entries(tracerConfig.env)) {
-        core.exportVariable(key, value);
+        actionState.env.export(key, value);
       }
     }
 
@@ -751,18 +748,18 @@ async function run(
     if (await features.getValue(Feature.JavaNetworkDebugging)) {
       // Get the existing value of `JAVA_TOOL_OPTIONS`, if any.
       const existingJavaToolOptions =
-        getOptionalEnvVar(JavaEnvVars.JAVA_TOOL_OPTIONS) || "";
+        actionState.env.getOptional(JavaEnvVars.JAVA_TOOL_OPTIONS) ?? "";
 
       // Add the network debugging options.
-      core.exportVariable(
+      actionState.env.export(
         JavaEnvVars.JAVA_TOOL_OPTIONS,
         `${existingJavaToolOptions} -Djavax.net.debug=all`,
       );
     }
 
-    // Write diagnostics to the database that we previously stored in memory because the database
-    // did not exist until now.
-    flushDiagnostics(config);
+    // Move diagnostics to the database that we previously kept in a temporary location
+    // because the database did not exist until now
+    flushDiagnostics(actionState, config);
 
     // We save the config here instead of at the end of `initConfig` because we
     // may have updated the config returned from `initConfig`, e.g. to revert to
@@ -791,7 +788,7 @@ async function run(
     );
     return;
   } finally {
-    logUnwrittenDiagnostics();
+    logTemporaryDiagnostics(actionState);
   }
   await sendCompletedStatusReport(
     startedAt,

src/init.test.ts

@@ -1,14 +1,13 @@
 import * as fs from "fs";
 import path from "path";
 
-import * as core from "@actions/core";
 import * as github from "@actions/github";
 import test, { ExecutionContext } from "ava";
 import * as sinon from "sinon";
 
 import * as actionsUtil from "./actions-util";
 import { createStubCodeQL } from "./codeql";
-import { ActionsEnvVars } from "./environment";
+import * as environment from "./environment";
 import { Feature } from "./feature-flags";
 import {
   checkPacksForOverlayCompatibility,
@@ -85,7 +84,7 @@ for (const { runnerEnv, ErrorConstructor, message } of [
     `cleanupDatabaseClusterDirectory throws a ${ErrorConstructor.name} when cleanup fails on ${runnerEnv} runner`,
     async (t) => {
       await withTmpDir(async (tmpDir: string) => {
-        process.env[ActionsEnvVars.RUNNER_ENVIRONMENT] = runnerEnv;
+        process.env[environment.ActionsEnvVars.RUNNER_ENVIRONMENT] = runnerEnv;
 
         const dbLocation = path.resolve(tmpDir, "dbs");
         fs.mkdirSync(dbLocation, { recursive: true });
@@ -546,7 +545,7 @@ test.serial(
 test.serial(
   "file coverage deprecation warning for org-owned repo with default setup recommends repo property",
   (t) => {
-    const exportVariableStub = sinon.stub(core, "exportVariable");
+    const exportEnvVarStub = sinon.stub(environment, "exportEnvVar");
     sinon.stub(actionsUtil, "isDefaultSetup").returns(true);
     github.context.payload = {
       repository: {
@@ -566,14 +565,14 @@ test.serial(
         'with the name `github-codeql-file-coverage-on-prs` and the type "True/false", then set this property to ' +
         "`true` in the repository's settings.",
     );
-    t.true(exportVariableStub.calledOnce);
+    t.true(exportEnvVarStub.calledOnce);
   },
 );
 
 test.serial(
   "file coverage deprecation warning for org-owned repo with advanced setup recommends env var and repo property",
   (t) => {
-    const exportVariableStub = sinon.stub(core, "exportVariable");
+    const exportEnvVarStub = sinon.stub(environment, "exportEnvVar");
     sinon.stub(actionsUtil, "isDefaultSetup").returns(false);
     github.context.payload = {
       repository: {
@@ -594,14 +593,14 @@ test.serial(
         'with the name `github-codeql-file-coverage-on-prs` and the type "True/false", then set this property to ' +
         "`true` in the repository's settings.",
     );
-    t.true(exportVariableStub.calledOnce);
+    t.true(exportEnvVarStub.calledOnce);
   },
 );
 
 test.serial(
   "file coverage deprecation warning for user-owned repo with default setup recommends advanced setup",
   (t) => {
-    const exportVariableStub = sinon.stub(core, "exportVariable");
+    const exportEnvVarStub = sinon.stub(environment, "exportEnvVar");
     sinon.stub(actionsUtil, "isDefaultSetup").returns(true);
     github.context.payload = {
       repository: {
@@ -620,14 +619,14 @@ test.serial(
         "To opt out of this change, switch to an advanced setup workflow and " +
         "set the `CODEQL_ACTION_FILE_COVERAGE_ON_PRS` environment variable to `true`.",
     );
-    t.true(exportVariableStub.calledOnce);
+    t.true(exportEnvVarStub.calledOnce);
   },
 );
 
 test.serial(
   "file coverage deprecation warning for user-owned repo with advanced setup recommends env var",
   (t) => {
-    const exportVariableStub = sinon.stub(core, "exportVariable");
+    const exportEnvVarStub = sinon.stub(environment, "exportEnvVar");
     sinon.stub(actionsUtil, "isDefaultSetup").returns(false);
     github.context.payload = {
       repository: {
@@ -645,14 +644,14 @@ test.serial(
         "to improve analysis performance. File coverage information will still be computed on non-PR analyses.\n\n" +
         "To opt out of this change, set the `CODEQL_ACTION_FILE_COVERAGE_ON_PRS` environment variable to `true`.",
     );
-    t.true(exportVariableStub.calledOnce);
+    t.true(exportEnvVarStub.calledOnce);
   },
 );
 
 test.serial(
   "file coverage deprecation warning for unknown owner type with default setup recommends advanced setup",
   (t) => {
-    const exportVariableStub = sinon.stub(core, "exportVariable");
+    const exportEnvVarStub = sinon.stub(environment, "exportEnvVar");
     sinon.stub(actionsUtil, "isDefaultSetup").returns(true);
     github.context.payload = { repository: undefined };
     const messages: LoggedMessage[] = [];
@@ -666,14 +665,14 @@ test.serial(
         "To opt out of this change, switch to an advanced setup workflow and " +
         "set the `CODEQL_ACTION_FILE_COVERAGE_ON_PRS` environment variable to `true`.",
     );
-    t.true(exportVariableStub.calledOnce);
+    t.true(exportEnvVarStub.calledOnce);
   },
 );
 
 test.serial(
   "file coverage deprecation warning for unknown owner type with advanced setup recommends env var",
   (t) => {
-    const exportVariableStub = sinon.stub(core, "exportVariable");
+    const exportEnvVarStub = sinon.stub(environment, "exportEnvVar");
     sinon.stub(actionsUtil, "isDefaultSetup").returns(false);
     github.context.payload = { repository: undefined };
     const messages: LoggedMessage[] = [];
@@ -686,7 +685,7 @@ test.serial(
         "to improve analysis performance. File coverage information will still be computed on non-PR analyses.\n\n" +
         "To opt out of this change, set the `CODEQL_ACTION_FILE_COVERAGE_ON_PRS` environment variable to `true`.",
     );
-    t.true(exportVariableStub.calledOnce);
+    t.true(exportEnvVarStub.calledOnce);
   },
 );
 
@@ -695,10 +694,10 @@ test.serial(
   (t) => {
     process.env["CODEQL_ACTION_DID_LOG_FILE_COVERAGE_ON_PRS_DEPRECATION"] =
       "true";
-    const exportVariableStub = sinon.stub(core, "exportVariable");
+    const exportEnvVarStub = sinon.stub(environment, "exportEnvVar");
     const messages: LoggedMessage[] = [];
     logFileCoverageOnPrsDeprecationWarning(getRecordingLogger(messages));
     t.is(messages.length, 0);
-    t.true(exportVariableStub.notCalled);
+    t.true(exportEnvVarStub.notCalled);
   },
 );

src/init.ts

@@ -1,7 +1,6 @@
 import * as fs from "fs";
 import * as path from "path";
 
-import * as core from "@actions/core";
 import * as toolrunner from "@actions/exec/lib/toolrunner";
 import * as github from "@actions/github";
 import * as io from "@actions/io";
@@ -17,7 +16,7 @@ import {
 import { GitHubApiDetails } from "./api-client";
 import { CodeQL, setupCodeQL } from "./codeql";
 import * as configUtils from "./config-utils";
-import { EnvVar } from "./environment";
+import { EnvVar, exportEnvVar } from "./environment";
 import {
   CodeQLDefaultVersionInfo,
   Feature,
@@ -411,5 +410,5 @@ export function logFileCoverageOnPrsDeprecationWarning(logger: Logger): void {
   }
 
   logger.warning(message);
-  core.exportVariable(EnvVar.DID_LOG_FILE_COVERAGE_ON_PRS_DEPRECATION, "true");
+  exportEnvVar(EnvVar.DID_LOG_FILE_COVERAGE_ON_PRS_DEPRECATION, "true");
 }

src/languages/swift.test.ts

@@ -0,0 +1,589 @@
+import * as fs from "fs";
+
+import test from "ava";
+import * as sinon from "sinon";
+
+import { getCodeQLForTesting } from "../codeql";
+import * as diagnostics from "../diagnostics";
+import { ActionsEnvVars } from "../environment";
+import { Feature } from "../feature-flags";
+import { FileSystem } from "../fs";
+import {
+  checkExpectedLogMessages,
+  checkUnexpectedLogMessages,
+  createFeatures,
+  createTestConfig,
+  getTestEnv,
+  initAllState,
+  makeVersionInfo,
+  RecordingLogger,
+  setupTests,
+} from "../testing-utils";
+import { ToolsFeature } from "../tools-features";
+import { withTmpDir } from "../util";
+
+import {
+  isSwiftCompatible,
+  XCODE_SELECT_LINK_PATH,
+  xcodeVersion,
+} from "./swift";
+
+import { BuiltInLanguage } from ".";
+
+setupTests(test);
+
+type RequiredFS = FileSystem<"statSync" | "readlinkSync">;
+
+/**
+ * Sets up a suitable mock `FileSystem` for use with `xcodeVersion`.
+ *
+ * @param statSyncResult The result of `statSync`.
+ * @param readlinkSyncResult The result of `readlinkSync`.
+ *
+ * @returns The mocked `FileSystem` and stubs.
+ */
+function mockFs(
+  statSyncResult: boolean | Error,
+  readlinkSyncResult: string = "",
+) {
+  const stubbedFs: RequiredFS = {
+    statSync: fs.statSync,
+    readlinkSync: fs.readlinkSync,
+  };
+  const statSync = sinon.stub(stubbedFs, "statSync");
+
+  if (typeof statSyncResult === "boolean") {
+    statSync.returns({ isSymbolicLink: () => statSyncResult } as fs.Stats);
+  } else {
+    statSync.throws(new Error("ENOENT"));
+  }
+
+  const readlinkSync = sinon
+    .stub(stubbedFs, "readlinkSync")
+    .returns(readlinkSyncResult);
+
+  return { stubbedFs, statSync, readlinkSync };
+}
+
+test("xcodeVersion returns undefined if symlink doesn't exist", (t) => {
+  const logger = new RecordingLogger();
+
+  const { stubbedFs, statSync } = mockFs(new Error("ENOENT"));
+
+  t.is(xcodeVersion(logger, stubbedFs), undefined);
+  t.is(statSync.callCount, 1);
+  t.deepEqual(statSync.args[0], [XCODE_SELECT_LINK_PATH]);
+
+  checkExpectedLogMessages(t, logger.messages, [
+    "Unable to determine Xcode version: ENOENT",
+  ]);
+});
+
+test("xcodeVersion returns undefined if file is not a symlink", (t) => {
+  const logger = new RecordingLogger();
+
+  const { stubbedFs, statSync } = mockFs(false);
+
+  t.is(xcodeVersion(logger, stubbedFs), undefined);
+  t.is(statSync.callCount, 1);
+  t.deepEqual(statSync.args[0], [XCODE_SELECT_LINK_PATH]);
+
+  checkExpectedLogMessages(t, logger.messages, [
+    "exists, but is not a symbolic link",
+  ]);
+});
+
+test("xcodeVersion returns undefined if resolving the symlink returns nothing", (t) => {
+  const logger = new RecordingLogger();
+
+  const { stubbedFs, statSync, readlinkSync } = mockFs(true);
+
+  t.is(xcodeVersion(logger, stubbedFs), undefined);
+  t.is(statSync.callCount, 1);
+  t.deepEqual(statSync.args[0], [XCODE_SELECT_LINK_PATH]);
+  t.is(readlinkSync.callCount, 1);
+  t.deepEqual(readlinkSync.args[0], [XCODE_SELECT_LINK_PATH]);
+
+  checkExpectedLogMessages(t, logger.messages, [
+    "unexpectedly returned nothing",
+  ]);
+});
+
+test("xcodeVersion returns undefined if resolved path doesn't include pattern", (t) => {
+  const logger = new RecordingLogger();
+
+  const { stubbedFs, statSync, readlinkSync } = mockFs(
+    true,
+    "/Applications/Xcode.app/Contents/Developer",
+  );
+
+  t.is(xcodeVersion(logger, stubbedFs), undefined);
+  t.is(statSync.callCount, 1);
+  t.deepEqual(statSync.args[0], [XCODE_SELECT_LINK_PATH]);
+  t.is(readlinkSync.callCount, 1);
+  t.deepEqual(readlinkSync.args[0], [XCODE_SELECT_LINK_PATH]);
+
+  checkExpectedLogMessages(t, logger.messages, [
+    "does not contain expected pattern",
+  ]);
+});
+
+test("xcodeVersion returns undefined if match can't be parsed", (t) => {
+  const logger = new RecordingLogger();
+
+  const { stubbedFs, statSync, readlinkSync } = mockFs(
+    true,
+    "/Applications/Xcode_00.0.app/Contents/Developer",
+  );
+
+  t.is(xcodeVersion(logger, stubbedFs), undefined);
+  t.is(statSync.callCount, 1);
+  t.deepEqual(statSync.args[0], [XCODE_SELECT_LINK_PATH]);
+  t.is(readlinkSync.callCount, 1);
+  t.deepEqual(readlinkSync.args[0], [XCODE_SELECT_LINK_PATH]);
+
+  checkExpectedLogMessages(t, logger.messages, [
+    "Couldn't parse '00.0' as a semantic version.",
+  ]);
+});
+
+test("xcodeVersion returns version from resolved path", (t) => {
+  const logger = new RecordingLogger();
+
+  const { stubbedFs, statSync, readlinkSync } = mockFs(
+    true,
+    "/Applications/Xcode_16.4.app/Contents/Developer",
+  );
+
+  const result = xcodeVersion(logger, stubbedFs);
+
+  if (t.truthy(result)) {
+    t.is(result.major, 16);
+    t.is(result.minor, 4);
+  }
+
+  t.is(statSync.callCount, 1);
+  t.deepEqual(statSync.args[0], [XCODE_SELECT_LINK_PATH]);
+  t.is(readlinkSync.callCount, 1);
+  t.deepEqual(readlinkSync.args[0], [XCODE_SELECT_LINK_PATH]);
+});
+
+test("isSwiftCompatible doesn't throw for non-Swift languages", async (t) => {
+  for (const language of Object.values(BuiltInLanguage)) {
+    if (language === BuiltInLanguage.swift) {
+      continue;
+    }
+
+    const codeql = await getCodeQLForTesting();
+    await t.notThrowsAsync(
+      isSwiftCompatible(
+        initAllState(),
+        createTestConfig({ languages: [language] }),
+        codeql,
+      ),
+    );
+  }
+});
+
+test("isSwiftCompatible doesn't throw for Swift if CLI supports swiftSupportsAllPlatforms", async (t) =>
+  withTmpDir(async (tmpDir) => {
+    const logger = new RecordingLogger();
+    const env = getTestEnv();
+    env.set(ActionsEnvVars.RUNNER_TEMP, tmpDir);
+
+    const codeql = await getCodeQLForTesting("codeql-for-testing", logger, env);
+    const supportsFeature = sinon
+      .stub(codeql, "supportsFeature")
+      .withArgs(ToolsFeature.SwiftSupportsAllPlatforms)
+      .resolves(true);
+
+    await t.notThrowsAsync(
+      isSwiftCompatible(
+        initAllState({ platform: "darwin", env, logger }),
+        createTestConfig({ languages: [BuiltInLanguage.swift] }),
+        codeql,
+      ),
+    );
+
+    t.is(supportsFeature.callCount, 1);
+    t.deepEqual(supportsFeature.args[0], [
+      ToolsFeature.SwiftSupportsAllPlatforms,
+    ]);
+  }));
+
+test("isSwiftCompatible doesn't throw for Swift on darwin", async (t) =>
+  withTmpDir(async (tmpDir) => {
+    const logger = new RecordingLogger();
+    const env = getTestEnv();
+    env.set(ActionsEnvVars.RUNNER_TEMP, tmpDir);
+
+    const codeql = await getCodeQLForTesting("codeql-for-testing", logger, env);
+    sinon.stub(codeql, "getVersion").resolves(makeVersionInfo("2.27.0"));
+
+    await t.notThrowsAsync(
+      isSwiftCompatible(
+        initAllState({ platform: "darwin", env, logger }),
+        createTestConfig({ languages: [BuiltInLanguage.swift] }),
+        codeql,
+      ),
+    );
+  }));
+
+const nonDarwinPlatforms: NodeJS.Platform[] = ["linux", "win32"];
+for (const nonDarwinPlatform of nonDarwinPlatforms) {
+  test(`isSwiftCompatible throws for Swift on ${nonDarwinPlatform}`, async (t) =>
+    withTmpDir(async (tmpDir) => {
+      const logger = new RecordingLogger();
+      const env = getTestEnv();
+      env.set(ActionsEnvVars.RUNNER_TEMP, tmpDir);
+
+      const codeql = await getCodeQLForTesting(
+        "codeql-for-testing",
+        logger,
+        env,
+      );
+      sinon.stub(codeql, "getVersion").resolves(makeVersionInfo("2.27.0"));
+
+      await t.throwsAsync(
+        isSwiftCompatible(
+          initAllState({ platform: nonDarwinPlatform, env, logger }),
+          createTestConfig({ languages: [BuiltInLanguage.swift] }),
+          codeql,
+        ),
+      );
+    }));
+}
+
+test("isSwiftCompatible warns if version string is not a semver", async (t) =>
+  withTmpDir(async (tmpDir) => {
+    const logger = new RecordingLogger();
+    const env = getTestEnv();
+    env.set(ActionsEnvVars.RUNNER_TEMP, tmpDir);
+
+    const codeql = await getCodeQLForTesting("codeql-for-testing", logger, env);
+    sinon.stub(codeql, "getVersion").resolves(makeVersionInfo("2.27.0"));
+
+    await isSwiftCompatible(
+      initAllState({
+        logger,
+        platform: "darwin",
+        osRelease: "unexpected",
+        env,
+      }),
+      createTestConfig({ languages: [BuiltInLanguage.swift] }),
+      codeql,
+    );
+
+    checkExpectedLogMessages(t, logger.messages, [
+      "Unable to determine version of macOS, got: unexpected",
+    ]);
+  }));
+
+// `addDiagnostic` changes global state and we must stub it, so this test must be serial.
+test.serial(
+  "isSwiftCompatible logs and adds diagnostic if macOS version is unsupported",
+  async (t) =>
+    withTmpDir(async (tmpDir) => {
+      const logger = new RecordingLogger();
+      const env = getTestEnv();
+      env.set(ActionsEnvVars.RUNNER_TEMP, tmpDir);
+
+      const codeql = await getCodeQLForTesting(
+        "codeql-for-testing",
+        logger,
+        env,
+      );
+      sinon.stub(codeql, "getVersion").resolves(makeVersionInfo("2.27.0"));
+
+      const addDiagnostic = sinon.stub(diagnostics, "addDiagnostic");
+
+      const config = createTestConfig({ languages: [BuiltInLanguage.swift] });
+      await isSwiftCompatible(
+        initAllState({
+          logger,
+          platform: "darwin",
+          osRelease: "27.0.0",
+          env,
+        }),
+        config,
+        codeql,
+      );
+
+      checkExpectedLogMessages(t, logger.messages, [
+        "Traced Swift analysis is not supported on macOS 27",
+      ]);
+
+      t.is(addDiagnostic.callCount, 1);
+      t.like(addDiagnostic.args[0], [
+        config,
+        BuiltInLanguage.swift,
+        {
+          attributes: {
+            languages: [BuiltInLanguage.swift],
+            macOSVersion: "27.0.0",
+          },
+          severity: "warning",
+          source: {
+            id: "codeql-action/unsupported-traced-swift-analysis-macos",
+            name: "Traced Swift analysis is not supported on this version of macOS",
+          },
+          visibility: {
+            cliSummaryTable: true,
+            statusPage: true,
+            telemetry: true,
+          },
+        } satisfies Partial<diagnostics.DiagnosticMessage>,
+      ]);
+    }),
+);
+
+// `addDiagnostic` changes global state and we must stub it, so this test must be serial.
+test.serial(
+  "isSwiftCompatible throws if macOS version is unsupported and FF is enabled",
+  async (t) =>
+    withTmpDir(async (tmpDir) => {
+      const logger = new RecordingLogger();
+      const env = getTestEnv();
+      env.set(ActionsEnvVars.RUNNER_TEMP, tmpDir);
+
+      const features = createFeatures([
+        Feature.SwiftSkipUnsupportedTracedAnalysis,
+      ]);
+
+      const codeql = await getCodeQLForTesting(
+        "codeql-for-testing",
+        logger,
+        env,
+      );
+      sinon.stub(codeql, "getVersion").resolves(makeVersionInfo("2.27.0"));
+
+      const addDiagnostic = sinon.stub(diagnostics, "addDiagnostic");
+
+      const config = createTestConfig({ languages: [BuiltInLanguage.swift] });
+      await t.throwsAsync(
+        isSwiftCompatible(
+          initAllState({
+            logger,
+            platform: "darwin",
+            osRelease: "27.0.0",
+            env,
+            features,
+          }),
+          config,
+          codeql,
+        ),
+      );
+
+      t.is(addDiagnostic.callCount, 1);
+      t.like(addDiagnostic.args[0], [
+        config,
+        BuiltInLanguage.swift,
+        {
+          attributes: {
+            languages: [BuiltInLanguage.swift],
+            macOSVersion: "27.0.0",
+          },
+          severity: "error",
+          source: {
+            id: "codeql-action/unsupported-traced-swift-analysis-macos",
+            name: "Traced Swift analysis is not supported on this version of macOS",
+          },
+          visibility: {
+            cliSummaryTable: true,
+            statusPage: true,
+            telemetry: true,
+          },
+        } satisfies Partial<diagnostics.DiagnosticMessage>,
+      ]);
+    }),
+);
+
+// `addDiagnostic` changes global state and we must stub it, so this test must be serial.
+test.serial(
+  "isSwiftCompatible doesn't add a diagnostic if Xcode version is supported",
+  async (t) =>
+    withTmpDir(async (tmpDir) => {
+      const logger = new RecordingLogger();
+      const env = getTestEnv();
+      env.set(ActionsEnvVars.RUNNER_TEMP, tmpDir);
+
+      const { stubbedFs, statSync, readlinkSync } = mockFs(
+        true,
+        "/Applications/Xcode_26.0.app/Contents/Developer",
+      );
+
+      const codeql = await getCodeQLForTesting(
+        "codeql-for-testing",
+        logger,
+        env,
+      );
+      sinon.stub(codeql, "getVersion").resolves(makeVersionInfo("2.27.0"));
+
+      const addDiagnostic = sinon.stub(diagnostics, "addDiagnostic");
+
+      const config = createTestConfig({ languages: [BuiltInLanguage.swift] });
+      await isSwiftCompatible(
+        initAllState({
+          logger,
+          platform: "darwin",
+          osRelease: "26.0.0",
+          env,
+          fs: stubbedFs as FileSystem,
+        }),
+        config,
+        codeql,
+      );
+
+      t.is(statSync.callCount, 1);
+      t.deepEqual(statSync.args[0], [XCODE_SELECT_LINK_PATH]);
+      t.is(readlinkSync.callCount, 1);
+      t.deepEqual(readlinkSync.args[0], [XCODE_SELECT_LINK_PATH]);
+
+      checkUnexpectedLogMessages(t, logger.messages, [
+        "Traced Swift analysis is not supported on Xcode 27",
+      ]);
+
+      t.is(addDiagnostic.callCount, 0);
+    }),
+);
+
+// `addDiagnostic` changes global state and we must stub it, so this test must be serial.
+test.serial(
+  "isSwiftCompatible logs and adds diagnostic if Xcode version is unsupported",
+  async (t) =>
+    withTmpDir(async (tmpDir) => {
+      const logger = new RecordingLogger();
+      const env = getTestEnv();
+      env.set(ActionsEnvVars.RUNNER_TEMP, tmpDir);
+
+      const { stubbedFs, statSync, readlinkSync } = mockFs(
+        true,
+        "/Applications/Xcode_27.0.app/Contents/Developer",
+      );
+
+      const codeql = await getCodeQLForTesting(
+        "codeql-for-testing",
+        logger,
+        env,
+      );
+      sinon.stub(codeql, "getVersion").resolves(makeVersionInfo("2.27.0"));
+
+      const addDiagnostic = sinon.stub(diagnostics, "addDiagnostic");
+
+      const config = createTestConfig({ languages: [BuiltInLanguage.swift] });
+      await isSwiftCompatible(
+        initAllState({
+          logger,
+          platform: "darwin",
+          osRelease: "26.0.0",
+          env,
+          fs: stubbedFs as FileSystem,
+        }),
+        config,
+        codeql,
+      );
+
+      t.is(statSync.callCount, 1);
+      t.deepEqual(statSync.args[0], [XCODE_SELECT_LINK_PATH]);
+      t.is(readlinkSync.callCount, 1);
+      t.deepEqual(readlinkSync.args[0], [XCODE_SELECT_LINK_PATH]);
+
+      checkExpectedLogMessages(t, logger.messages, [
+        "Traced Swift analysis is not supported on Xcode 27",
+      ]);
+
+      t.is(addDiagnostic.callCount, 1);
+      t.like(addDiagnostic.args[0], [
+        config,
+        BuiltInLanguage.swift,
+        {
+          attributes: {
+            languages: [BuiltInLanguage.swift],
+            xcodeVersion: "27.0.0",
+          },
+          severity: "warning",
+          source: {
+            id: "codeql-action/unsupported-traced-swift-analysis-xcode",
+            name: "Traced Swift analysis is not supported on this version of Xcode",
+          },
+          visibility: {
+            cliSummaryTable: true,
+            statusPage: true,
+            telemetry: true,
+          },
+        } satisfies Partial<diagnostics.DiagnosticMessage>,
+      ]);
+    }),
+);
+
+// `addDiagnostic` changes global state and we must stub it, so this test must be serial.
+test.serial(
+  "isSwiftCompatible throws if Xcode version is unsupported and FF is enabled",
+  async (t) =>
+    withTmpDir(async (tmpDir) => {
+      const logger = new RecordingLogger();
+      const env = getTestEnv();
+      env.set(ActionsEnvVars.RUNNER_TEMP, tmpDir);
+
+      const { stubbedFs, statSync, readlinkSync } = mockFs(
+        true,
+        "/Applications/Xcode_27.0.app/Contents/Developer",
+      );
+
+      const features = createFeatures([
+        Feature.SwiftSkipUnsupportedTracedAnalysis,
+      ]);
+
+      const codeql = await getCodeQLForTesting(
+        "codeql-for-testing",
+        logger,
+        env,
+      );
+      sinon.stub(codeql, "getVersion").resolves(makeVersionInfo("2.27.0"));
+
+      const addDiagnostic = sinon.stub(diagnostics, "addDiagnostic");
+
+      const config = createTestConfig({ languages: [BuiltInLanguage.swift] });
+      await t.throwsAsync(
+        isSwiftCompatible(
+          initAllState({
+            logger,
+            platform: "darwin",
+            osRelease: "26.0.0",
+            env,
+            features,
+            fs: stubbedFs as FileSystem,
+          }),
+          config,
+          codeql,
+        ),
+      );
+
+      t.is(statSync.callCount, 1);
+      t.deepEqual(statSync.args[0], [XCODE_SELECT_LINK_PATH]);
+      t.is(readlinkSync.callCount, 1);
+      t.deepEqual(readlinkSync.args[0], [XCODE_SELECT_LINK_PATH]);
+
+      t.is(addDiagnostic.callCount, 1);
+      t.like(addDiagnostic.args[0], [
+        config,
+        BuiltInLanguage.swift,
+        {
+          attributes: {
+            languages: [BuiltInLanguage.swift],
+            xcodeVersion: "27.0.0",
+          },
+          severity: "error",
+          source: {
+            id: "codeql-action/unsupported-traced-swift-analysis-xcode",
+            name: "Traced Swift analysis is not supported on this version of Xcode",
+          },
+          visibility: {
+            cliSummaryTable: true,
+            statusPage: true,
+            telemetry: true,
+          },
+        } satisfies Partial<diagnostics.DiagnosticMessage>,
+      ]);
+    }),
+);

src/languages/swift.ts

@@ -0,0 +1,218 @@
+import * as semver from "semver";
+
+import { ActionState, Logger } from "../action-common";
+import { CodeQL } from "../codeql";
+import { Config } from "../config-utils";
+import { addDiagnostic, makeDiagnostic } from "../diagnostics";
+import { Feature } from "../feature-flags";
+import { FileSystem } from "../fs";
+import { macOSVersion } from "../platform";
+import { ToolsFeature } from "../tools-features";
+import { ConfigurationError, getErrorMessage } from "../util";
+
+import { BuiltInLanguage } from ".";
+
+/** The static path we check for a symbolic link to the (dynamic) Xcode location. */
+export const XCODE_SELECT_LINK_PATH = "/private/var/db/xcode_select_link";
+
+/** The pattern we expect to find in the Xcode path. */
+export const XCODE_APP_FILENAME_PATTERN = new RegExp(
+  /(?<filename>Xcode_(?<majorMinor>\d+.\d+).app)/,
+);
+
+/** macOS 27 and above do not support traced extraction for Swift. */
+export const SWIFT_TRACED_UNSUPPORTED_MACOS = 27;
+
+/** Xcode 27 and above do not support traced extraction for Swift. */
+export const SWIFT_TRACED_UNSUPPORTED_XCODE = 27;
+
+/**
+ * Tries to determine the version of Xcode that is installed.
+ *
+ * @param logger The logger to use.
+ * @returns The Xcode version or `undefined` if it couldn't be determined.
+ */
+export function xcodeVersion(
+  logger: Logger,
+  fs: FileSystem<"statSync" | "readlinkSync">,
+): semver.SemVer | undefined {
+  try {
+    // Stat the expected symbolic link to check that it exists and is a symbolic link.
+    // The `readlinkSync` call below returns an empty string in either case and so
+    // this check allows us to distinguish between the two cases.
+    const stats = fs.statSync(XCODE_SELECT_LINK_PATH);
+
+    if (!stats.isSymbolicLink()) {
+      logger.warning(
+        `${XCODE_SELECT_LINK_PATH} exists, but is not a symbolic link.`,
+      );
+      return undefined;
+    }
+
+    // Read what the symbolic link points to.
+    const xcodePath = fs.readlinkSync(XCODE_SELECT_LINK_PATH);
+
+    if (xcodePath === "") {
+      logger.warning(
+        `Resolving ${XCODE_SELECT_LINK_PATH} unexpectedly returned nothing.`,
+      );
+      return undefined;
+    }
+
+    // Try to extract the version from the path.
+    const matchResult = xcodePath.match(XCODE_APP_FILENAME_PATTERN);
+
+    if (matchResult?.groups === undefined) {
+      logger.warning(
+        `Xcode path '${xcodePath}' does not contain expected pattern.`,
+      );
+      return undefined;
+    }
+
+    const majorMinor = matchResult.groups["majorMinor"];
+    const version = semver.coerce(majorMinor);
+
+    if (version === null) {
+      logger.warning(`Couldn't parse '${majorMinor}' as a semantic version.`);
+      return undefined;
+    }
+    return version;
+  } catch (err) {
+    logger.warning(
+      `Unable to determine Xcode version: ${getErrorMessage(err)}`,
+    );
+    return undefined;
+  }
+}
+
+/**
+ * Creates a diagnostic indicating that `version` of `product` is unsupported for traced Swift analysis.
+ * Depending on `skipUnsupportedTracedAnalysis`, this function then either throws a {@link ConfigurationError}
+ * or logs the problem as a warning.
+ *
+ * @param logger The logger to use.
+ * @param config The CodeQL Action configuration.
+ * @param skipUnsupportedTracedAnalysis Whether this is a fatal error.
+ * @param product The product that the version is unsupported of.
+ * @param version The unsupported version.
+ */
+function handleUnsupportedVersion(
+  logger: Logger,
+  config: Config,
+  skipUnsupportedTracedAnalysis: boolean,
+  product: "macOS" | "Xcode",
+  version: semver.SemVer,
+) {
+  const baseMessage = [
+    `Traced Swift analysis is not supported on ${product} ${SWIFT_TRACED_UNSUPPORTED_MACOS} or above.`,
+    `Configure your analysis to run on macOS ${SWIFT_TRACED_UNSUPPORTED_MACOS - 1} or below`,
+    `and XCode ${SWIFT_TRACED_UNSUPPORTED_XCODE - 1} or below.`,
+  ].join(" ");
+
+  const attributeName = product === "macOS" ? "macOSVersion" : "xcodeVersion";
+
+  // Create a diagnostic that will show up on the TSP.
+  addDiagnostic(
+    config,
+    BuiltInLanguage.swift,
+    makeDiagnostic(
+      `codeql-action/unsupported-traced-swift-analysis-${product.toLowerCase()}`,
+      `Traced Swift analysis is not supported on this version of ${product}`,
+      {
+        attributes: {
+          languages: config.languages,
+          [attributeName]: version.toString(),
+        },
+        markdownMessage: baseMessage,
+        severity: skipUnsupportedTracedAnalysis ? "error" : "warning",
+        visibility: {
+          cliSummaryTable: true,
+          statusPage: true,
+          telemetry: true,
+        },
+      },
+    ),
+  );
+
+  // Throw an error to abort the analysis if the FF is enabled or log the message.
+  if (skipUnsupportedTracedAnalysis) {
+    // ConfigurationErrors are converted to the "aborted" status by the exception handler
+    // in `init-action.ts` that guards the call to `isSwiftCompatible`.
+    throw new ConfigurationError(baseMessage);
+  } else {
+    // This will also show up as a workflow annotation.
+    logger.warning(baseMessage);
+  }
+}
+
+/**
+ * Determines whether we can run a Swift analysis on the current runner.
+ *
+ * @param action The Action state.
+ * @param config The Action configuration.
+ *
+ * @throws {ConfigurationError} If Swift analysis is not possible on the current runner.
+ * @returns True if we can run a Swift analysis.
+ */
+export async function isSwiftCompatible(
+  action: ActionState<["Base", "Logger", "FeatureFlags", "FS"]>,
+  config: Config,
+  codeql: CodeQL,
+) {
+  // The checks are not relevant if we are not trying to analyse Swift.
+  if (!config.languages.includes(BuiltInLanguage.swift)) {
+    return;
+  }
+
+  // Skip the checks if the `swiftSupportsAllPlatforms` feature is supported by the CLI.
+  // This is a forward-looking measure that allows a future CLI update to disable these
+  // platform checks in the Action when they shouldn't be enforced anymore.
+  if (await codeql.supportsFeature(ToolsFeature.SwiftSupportsAllPlatforms)) {
+    return;
+  }
+
+  // Try to get the macOS version.
+  const version = macOSVersion(action);
+
+  // If `version` is undefined, then we are not on macOS.
+  if (version === undefined) {
+    throw new ConfigurationError(
+      `Swift analysis is only supported on macOS runner images. Please migrate to a macOS runner.`,
+    );
+  }
+
+  const skipUnsupportedTracedAnalysis = await action.features.getValue(
+    Feature.SwiftSkipUnsupportedTracedAnalysis,
+  );
+  if (typeof version === "string") {
+    // If we got a string, we are on macOS but couldn't parse the version string.
+    action.logger.warning(
+      `Unable to determine version of macOS, got: ${version}`,
+    );
+  } else if (version.major >= SWIFT_TRACED_UNSUPPORTED_MACOS) {
+    handleUnsupportedVersion(
+      action.logger,
+      config,
+      skipUnsupportedTracedAnalysis,
+      "macOS",
+      version,
+    );
+  }
+
+  // Determining whether the Xcode version is supported only makes sense on macOS, so we only do it
+  // after determining that we are running on macOS.
+  const xcodeVer = xcodeVersion(action.logger, action.fs);
+
+  if (
+    xcodeVer !== undefined &&
+    xcodeVer.major >= SWIFT_TRACED_UNSUPPORTED_XCODE
+  ) {
+    handleUnsupportedVersion(
+      action.logger,
+      config,
+      skipUnsupportedTracedAnalysis,
+      "Xcode",
+      xcodeVer,
+    );
+  }
+}

src/overlay/caching.test.ts

@@ -8,6 +8,7 @@ import * as sinon from "sinon";
 import * as actionsUtil from "../actions-util";
 import * as apiClient from "../api-client";
 import type { ResolveDatabaseOutput } from "../codeql";
+import * as environment from "../environment";
 import * as gitUtils from "../git-utils";
 import { BuiltInLanguage } from "../languages";
 import { getRunnerLogger } from "../logging";
@@ -82,7 +83,7 @@ const testDownloadOverlayBaseDatabaseFromCache = makeMacro({
 
       sinon.stub(apiClient, "getAutomationID").resolves("test-automation-id/");
 
-      sinon.stub(utils, "isInTestMode").returns(testCase.isInTestMode);
+      sinon.stub(environment, "isInTestMode").returns(testCase.isInTestMode);
 
       if (testCase.restoreCacheResult instanceof Error) {
         sinon

src/platform.test.ts

@@ -1,6 +1,7 @@
 import test from "ava";
 
-import { BundlePlatform, getBundlePlatform } from "./platform";
+import { BundlePlatform, getBundlePlatform, macOSVersion } from "./platform";
+import { initAllState } from "./testing-utils";
 
 for (const [platform, arch, expected] of [
   ["linux", "x64", BundlePlatform.Linux64],
@@ -16,3 +17,40 @@ for (const [platform, arch, expected] of [
     t.is(getBundlePlatform(platform, arch), expected);
   });
 }
+
+const platforms: NodeJS.Platform[] = ["linux", "win32", "freebsd"];
+for (const platform of platforms) {
+  test(`macOSVersion returns undefined on ${platform}`, (t) => {
+    t.is(macOSVersion(initAllState({ platform })), undefined);
+  });
+}
+
+test("macOSVersion returns raw string if semver parsing fails", (t) => {
+  const invalidSemVer = "sealOS-2026";
+  t.is(
+    macOSVersion(
+      initAllState({ platform: "darwin", osRelease: invalidSemVer }),
+    ),
+    invalidSemVer,
+  );
+});
+
+test("macOSVersion returns semver if parsing succeeds", (t) => {
+  const validSemVer = "27.0.1";
+
+  const version = macOSVersion(
+    initAllState({ platform: "darwin", osRelease: validSemVer }),
+  );
+
+  // Check that `version` is not undefined and narrow the type; throws if undefined.
+  if (t.truthy(version)) {
+    // Check that it's also not just a string.
+    t.not(typeof version, "string");
+
+    // Should be an object with the expected properties.
+    t.is(typeof version, "object");
+    t.is(version["major"], 27);
+    t.is(version["minor"], 0);
+    t.is(version["patch"], 1);
+  }
+});

src/platform.ts

@@ -1,3 +1,7 @@
+import * as semver from "semver";
+
+import type { ActionState } from "./action-common";
+
 /** Platform identifiers used in CodeQL bundle asset names. */
 export enum BundlePlatform {
   Linux64 = "linux64",
@@ -24,3 +28,28 @@ export function getBundlePlatform(
       return undefined;
   }
 }
+
+/**
+ * Tries to determine the version of macOS.
+ *
+ * @returns
+ *  The version as either a semantic version object, the raw version string
+ *  if it is not a semantic version, or `undefined` if we are not on macOS.
+ */
+export function macOSVersion(
+  action: ActionState<["Base"]>,
+): semver.SemVer | string | undefined {
+  // Skip if we are not running on macOS.
+  if (action.platform !== "darwin") {
+    return undefined;
+  }
+
+  // Try to parse the OS version string.
+  const version = semver.parse(action.osRelease);
+
+  if (version === null) {
+    return action.osRelease;
+  }
+
+  return version;
+}

src/setup-codeql-action.ts

@@ -184,7 +184,7 @@ async function run(
     core.setOutput("codeql-path", codeql.getPath());
     core.setOutput("codeql-version", (await codeql.getVersion()).version);
 
-    core.exportVariable(EnvVar.SETUP_CODEQL_ACTION_HAS_RUN, "true");
+    actionState.env.export(EnvVar.SETUP_CODEQL_ACTION_HAS_RUN, "true");
   } catch (unwrappedError) {
     const error = wrapError(unwrappedError);
     core.setFailed(error.message);

src/setup-codeql.test.ts

@@ -1647,16 +1647,20 @@ test.serial(
       },
     ]);
 
-    const result = await setupCodeql.getEnabledVersionsWithOverlayBaseDatabases(
-      overlayMatchEnabledVersions,
-      ["javascript"],
-      createFeatures([Feature.OverlayAnalysisMatchCodeqlVersion]),
-      getRunnerLogger(true),
-    );
-    t.deepEqual(result, [
-      { cliVersion: "2.20.1", tagName: "codeql-bundle-v2.20.1" },
-      { cliVersion: "2.20.0", tagName: "codeql-bundle-v2.20.0" },
-    ]);
+    await withTmpDir(async (tmpDir) => {
+      setupActionsVars(tmpDir, tmpDir);
+      const result =
+        await setupCodeql.getEnabledVersionsWithOverlayBaseDatabases(
+          overlayMatchEnabledVersions,
+          ["javascript"],
+          createFeatures([Feature.OverlayAnalysisMatchCodeqlVersion]),
+          getRunnerLogger(true),
+        );
+      t.deepEqual(result, [
+        { cliVersion: "2.20.1", tagName: "codeql-bundle-v2.20.1" },
+        { cliVersion: "2.20.0", tagName: "codeql-bundle-v2.20.0" },
+      ]);
+    });
   },
 );
 
@@ -1773,21 +1777,25 @@ test.serial(
       },
     ]);
 
-    const result = await setupCodeql.getEnabledVersionsWithOverlayBaseDatabases(
-      overlayMatchEnabledVersions,
-      ["javascript"],
-      createFeatures([Feature.OverlayAnalysisMatchCodeqlVersionDryRun]),
-      getRunnerLogger(true),
-    );
-    t.deepEqual(
-      result,
-      [],
-      "Dry-run should return an empty list so the caller falls back.",
-    );
-    t.assert(
-      listStub.calledOnce,
-      "Dry-run should still list Actions caches to populate the diagnostic.",
-    );
+    await withTmpDir(async (tmpDir) => {
+      setupActionsVars(tmpDir, tmpDir);
+      const result =
+        await setupCodeql.getEnabledVersionsWithOverlayBaseDatabases(
+          overlayMatchEnabledVersions,
+          ["javascript"],
+          createFeatures([Feature.OverlayAnalysisMatchCodeqlVersionDryRun]),
+          getRunnerLogger(true),
+        );
+      t.deepEqual(
+        result,
+        [],
+        "Dry-run should return an empty list so the caller falls back.",
+      );
+      t.assert(
+        listStub.calledOnce,
+        "Dry-run should still list Actions caches to populate the diagnostic.",
+      );
+    });
   },
 );
 
@@ -1801,18 +1809,22 @@ test.serial(
       },
     ]);
 
-    const result = await setupCodeql.getEnabledVersionsWithOverlayBaseDatabases(
-      overlayMatchEnabledVersions,
-      ["javascript"],
-      createFeatures([
-        Feature.OverlayAnalysisMatchCodeqlVersion,
-        Feature.OverlayAnalysisMatchCodeqlVersionDryRun,
-      ]),
-      getRunnerLogger(true),
-    );
-    t.deepEqual(result, [
-      { cliVersion: "2.20.1", tagName: "codeql-bundle-v2.20.1" },
-    ]);
+    await withTmpDir(async (tmpDir) => {
+      setupActionsVars(tmpDir, tmpDir);
+      const result =
+        await setupCodeql.getEnabledVersionsWithOverlayBaseDatabases(
+          overlayMatchEnabledVersions,
+          ["javascript"],
+          createFeatures([
+            Feature.OverlayAnalysisMatchCodeqlVersion,
+            Feature.OverlayAnalysisMatchCodeqlVersionDryRun,
+          ]),
+          getRunnerLogger(true),
+        );
+      t.deepEqual(result, [
+        { cliVersion: "2.20.1", tagName: "codeql-bundle-v2.20.1" },
+      ]);
+    });
   },
 );
 

src/setup-codeql.ts

@@ -3,7 +3,6 @@ import { OutgoingHttpHeaders } from "http";
 import * as path from "path";
 import { performance } from "perf_hooks";
 
-import * as core from "@actions/core";
 import * as toolcache from "@actions/tool-cache";
 import { default as deepEqual } from "fast-deep-equal";
 import * as semver from "semver";
@@ -29,7 +28,7 @@ import {
   makeDiagnostic,
   makeTelemetryDiagnostic,
 } from "./diagnostics";
-import { EnvVar, getEnv } from "./environment";
+import { EnvVar, exportEnvVar, getEnv } from "./environment";
 import {
   CODEQL_VERSION_ZSTD_BUNDLE,
   CodeQLDefaultVersionInfo,
@@ -1071,7 +1070,7 @@ export async function setupCodeQLBundle(
 
   // Record that this job now has a copy of the CodeQL tools, so that a later step doesn't delete
   // the toolcache out from under the path we are about to return.
-  core.exportVariable(EnvVar.HAS_SET_UP_CODEQL, "true");
+  exportEnvVar(EnvVar.HAS_SET_UP_CODEQL, "true");
 
   return {
     codeqlFolder,

src/status-report.ts

@@ -23,7 +23,13 @@ import type { ComputedInput, InputName } from "./config/inputs";
 import { parseRegistriesWithoutCredentials } from "./config/pack-registries";
 import type { DependencyCacheRestoreStatusReport } from "./dependency-caching";
 import { DocUrl } from "./doc-url";
-import { EnvVar, getEnv, ReadOnlyEnv, RegistryProxyVars } from "./environment";
+import {
+  EnvVar,
+  getEnv,
+  ReadOnlyEnv,
+  RegistryProxyVars,
+  exportEnvVar,
+} from "./environment";
 import { getRef } from "./git-utils";
 import * as json from "./json";
 import type { Logger } from "./logging";
@@ -71,9 +77,7 @@ export function getDisplayActionName(actionName: ActionName): string {
  * environment and returns it.
  * If a new UUID is generated, it is also exported as an environment variable.
  */
-export function getJobUUID(
-  action: ActionState<["Logger", "ReadOnlyEnv", "Actions"]>,
-) {
+export function getJobUUID(action: ActionState<["Logger", "Env", "Actions"]>) {
   // Check if we already have a UUID for the analysis and return it if so.
   const existingJobRunUuid = action.env.getOptional(EnvVar.JOB_RUN_UUID);
 
@@ -86,7 +90,7 @@ export function getJobUUID(
   const jobRunUuid = uuid.v4();
   action.logger.info(`Job run UUID is ${jobRunUuid}.`);
 
-  action.actions.exportVariable(EnvVar.JOB_RUN_UUID, jobRunUuid);
+  action.env.export(EnvVar.JOB_RUN_UUID, jobRunUuid);
   return jobRunUuid;
 }
 
@@ -268,12 +272,12 @@ export function getJobStatusDisplayName(status: JobStatus): string {
  */
 function setJobStatusIfUnsuccessful(actionStatus: ActionStatus) {
   if (actionStatus === "user-error") {
-    core.exportVariable(
+    exportEnvVar(
       EnvVar.JOB_STATUS,
       process.env[EnvVar.JOB_STATUS] ?? JobStatus.ConfigErrorStatus,
     );
   } else if (actionStatus === "failure" || actionStatus === "aborted") {
-    core.exportVariable(
+    exportEnvVar(
       EnvVar.JOB_STATUS,
       process.env[EnvVar.JOB_STATUS] ?? JobStatus.FailureStatus,
     );
@@ -376,7 +380,7 @@ export async function createStatusReportBase(
     let workflowStartedAt = process.env[EnvVar.WORKFLOW_STARTED_AT];
     if (workflowStartedAt === undefined) {
       workflowStartedAt = actionStartedAt.toISOString();
-      core.exportVariable(EnvVar.WORKFLOW_STARTED_AT, workflowStartedAt);
+      exportEnvVar(EnvVar.WORKFLOW_STARTED_AT, workflowStartedAt);
     }
     const runnerOs = getRequiredEnvParam("RUNNER_OS");
     const codeQlCliVersion = getCachedCodeQlVersion(
@@ -388,7 +392,7 @@ export async function createStatusReportBase(
     // re-export the testing environment variable so that it is available to subsequent steps,
     // even if it was only set for this step
     if (testingEnvironment) {
-      core.exportVariable(EnvVar.TESTING_ENVIRONMENT, testingEnvironment);
+      exportEnvVar(EnvVar.TESTING_ENVIRONMENT, testingEnvironment);
     }
     const isSteadyStateDefaultSetupRun =
       process.env["CODE_SCANNING_IS_STEADY_STATE_DEFAULT_SETUP"] === "true";

src/testing-utils.ts

@@ -1,4 +1,6 @@
+import * as fs from "fs";
 import { TextDecoder } from "node:util";
+import * as os from "os";
 import path from "path";
 
 import * as github from "@actions/github";
@@ -34,6 +36,7 @@ import { Logger } from "./logging";
 import { OverlayDatabaseMode } from "./overlay/overlay-database-mode";
 import { getBundlePlatform } from "./platform";
 import { ActionName } from "./status-report";
+import { ToolsFeature } from "./tools-features";
 import {
   DEFAULT_DEBUG_ARTIFACT_NAME,
   DEFAULT_DEBUG_DATABASE_NAME,
@@ -202,10 +205,6 @@ class TestActionsEnv implements ActionsEnv {
   public getOptionalInput(_name: string): string | undefined {
     return undefined;
   }
-
-  public exportVariable(name: string, value: string): void {
-    this.env.set(name, value);
-  }
 }
 
 /**
@@ -224,6 +223,7 @@ type AllState = [
   "Actions",
   "Api",
   "FeatureFlags",
+  "FS",
 ];
 
 /** Initialise a fresh `ActionState<AllState>` value. */
@@ -236,11 +236,13 @@ export function initAllState(
     startedAt: new Date(),
     platform: process.platform,
     arch: process.arch,
+    osRelease: os.release(),
     logger: new RecordingLogger(),
     env,
     actions: getTestActionsEnv(env),
     apiClient: github.getOctokit("123"),
     features: createFeatures([]),
+    fs,
     ...overrides,
   };
 }
@@ -874,7 +876,7 @@ export function mockLanguagesInRepo(languages: string[]) {
  */
 export const makeVersionInfo = (
   version: string,
-  features?: { [name: string]: boolean },
+  features?: { [key in ToolsFeature]?: boolean },
   overlayVersion?: number,
 ): VersionInfo => ({
   version,

src/tools-features.ts

@@ -8,6 +8,7 @@ export enum ToolsFeature {
   BundleSupportsOverlay = "bundleSupportsOverlay",
   IndirectTracingSupportsStaticBinaries = "indirectTracingSupportsStaticBinaries",
   SuppressesMissingFileBaselineWarning = "suppressesMissingFileBaselineWarning",
+  SwiftSupportsAllPlatforms = "swiftSupportsAllPlatforms",
 }
 
 /**

src/upload-lib.ts

@@ -14,7 +14,7 @@ import { getGitHubVersion, wrapApiConfigurationError } from "./api-client";
 import { CodeQL, getCodeQL } from "./codeql";
 import { getConfig } from "./config-utils";
 import { readDiffRangesJsonFile } from "./diff-informed-analysis-utils";
-import { EnvVar } from "./environment";
+import { EnvVar, exportEnvVar } from "./environment";
 import { FeatureEnablement } from "./feature-flags";
 import * as fingerprints from "./fingerprints";
 import * as gitUtils from "./git-utils";
@@ -126,7 +126,7 @@ async function combineSarifFilesUsingCLI(
       logger.warning(
         `Uploading multiple SARIF runs with the same category is deprecated ${deprecationWarningMessage}. Please update your workflow to upload a single run per category. ${deprecationMoreInformationMessage}`,
       );
-      core.exportVariable("CODEQL_MERGE_SARIF_DEPRECATION_WARNING", "true");
+      exportEnvVar("CODEQL_MERGE_SARIF_DEPRECATION_WARNING", "true");
     }
 
     // If not, use the naive method of combining the files.
@@ -1032,7 +1032,7 @@ export function validateUniqueCategory(
           `Category: (${id ? id : "none"}) Tool: (${tool ? tool : "none"})`,
       );
     }
-    core.exportVariable(sentinelEnvVar, sentinelEnvVar);
+    exportEnvVar(sentinelEnvVar, sentinelEnvVar);
   }
 }
 

src/util.ts

@@ -14,13 +14,23 @@ import * as apiCompatibility from "./api-compatibility.json";
 import type { CodeQL } from "./codeql";
 import type { Pack } from "./config/db-config";
 import type { Config } from "./config-utils";
-import { EnvVar, getRequiredEnvParam } from "./environment";
+import {
+  EnvVar,
+  getRequiredEnvParam,
+  isInTestMode,
+  exportEnvVar,
+} from "./environment";
 import * as json from "./json";
 import { Language } from "./languages";
 import { Logger } from "./logging";
 
 // Re-export for backwards compatibility to avoid updating a lot of imports elsewhere.
-export { getRequiredEnvParam, getOptionalEnvVar, getEnv } from "./environment";
+export {
+  getRequiredEnvParam,
+  getOptionalEnvVar,
+  getEnv,
+  isInTestMode,
+} from "./environment";
 
 /**
  * The name of the file containing the base database OIDs, as stored in the
@@ -542,7 +552,7 @@ export function checkGitHubVersionInRange(
     );
   }
   hasBeenWarnedAboutVersion = true;
-  core.exportVariable(CODEQL_ACTION_WARNED_ABOUT_VERSION_ENV_VAR, true);
+  exportEnvVar(CODEQL_ACTION_WARNED_ABOUT_VERSION_ENV_VAR, true);
 }
 
 export enum DisallowedAPIVersionReason {
@@ -586,11 +596,11 @@ export function assertNever(value: never): never {
  * knowing what version of CodeQL we're running.
  */
 export function initializeEnvironment(version: string) {
-  core.exportVariable(EnvVar.FEATURE_MULTI_LANGUAGE, "false");
-  core.exportVariable(EnvVar.FEATURE_SANDWICH, "false");
-  core.exportVariable(EnvVar.FEATURE_SARIF_COMBINE, "true");
-  core.exportVariable(EnvVar.FEATURE_WILL_UPLOAD, "true");
-  core.exportVariable(EnvVar.VERSION, version);
+  exportEnvVar(EnvVar.FEATURE_MULTI_LANGUAGE, "false");
+  exportEnvVar(EnvVar.FEATURE_SANDWICH, "false");
+  exportEnvVar(EnvVar.FEATURE_SARIF_COMBINE, "true");
+  exportEnvVar(EnvVar.FEATURE_WILL_UPLOAD, "true");
+  exportEnvVar(EnvVar.VERSION, version);
 }
 
 export class HTTPError extends Error {
@@ -711,15 +721,6 @@ export function isGoodVersion(versionSpec: string) {
   return !BROKEN_VERSIONS.includes(versionSpec);
 }
 
-/**
- * Returns whether we are in test mode. This is used by CodeQL Action PR checks.
- *
- * In test mode, we skip several uploads (SARIF results, status reports, DBs, ...).
- */
-export function isInTestMode(): boolean {
-  return process.env[EnvVar.TEST_MODE] === "true";
-}
-
 /**
  * Returns whether we specifically want to skip uploading SARIF files.
  */
@@ -948,7 +949,7 @@ export async function checkDiskUsage(
       } else {
         logger.debug(message);
       }
-      core.exportVariable(EnvVar.HAS_WARNED_ABOUT_DISK_SPACE, "true");
+      exportEnvVar(EnvVar.HAS_WARNED_ABOUT_DISK_SPACE, "true");
     }
     return {
       numAvailableBytes: diskUsage.bavail * blockSizeInBytes,
@@ -997,7 +998,7 @@ export function checkActionVersion(
           "https://github.blog/changelog/2025-10-28-upcoming-deprecation-of-codeql-action-v3/",
       );
       // set LOG_VERSION_DEPRECATION env var to prevent the warning from being logged multiple times
-      core.exportVariable(EnvVar.LOG_VERSION_DEPRECATION, "true");
+      exportEnvVar(EnvVar.LOG_VERSION_DEPRECATION, "true");
     }
   }
 }