From 739fc3a5308acc60ba24edaa59684296d2eae38c Mon Sep 17 00:00:00 2001
From: "Michael B. Gale" <mbg@github.com>
Date: Mon, 12 Oct 2026 15:27:32 +0100
Subject: [PATCH] Add and use `RepositoryNwoStr` type

---
 lib/entry-points.js     | 13 ++++++++++++-
 src/repository.ts       |  8 ++++++++
 src/setup/repository.ts | 19 +++++++++++++++----
 3 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/lib/entry-points.js b/lib/entry-points.js
index e4a956372..5e723fded 100644
--- a/lib/entry-points.js
+++ b/lib/entry-points.js
@@ -170638,6 +170638,9 @@ function getCurrentInstance(env) {
 }
 
 // src/repository.ts
+function isRepositoryNwoStr(val) {
+  return val.includes("/");
+}
 function getRepositoryNwo() {
   return getRepositoryNwoFromEnv("GITHUB_REPOSITORY");
 }
@@ -175719,7 +175722,15 @@ function getCodeQLActionRepository(action) {
     );
     return CODEQL_DEFAULT_ACTION_REPOSITORY;
   }
-  return action.env.getRequired("GITHUB_ACTION_REPOSITORY" /* GITHUB_ACTION_REPOSITORY */);
+  const actionRepository = action.env.getRequired(
+    "GITHUB_ACTION_REPOSITORY" /* GITHUB_ACTION_REPOSITORY */
+  );
+  if (isRepositoryNwoStr(actionRepository)) {
+    return actionRepository;
+  }
+  throw new Error(
+    `The value of '${"GITHUB_ACTION_REPOSITORY" /* GITHUB_ACTION_REPOSITORY */}' is '${actionRepository}', which does not match the expected 'owner/repo' format.`
+  );
 }
 var DEFAULT_DOWNLOAD_SOURCE = [
   GITHUB_DOTCOM_URL,
diff --git a/src/repository.ts b/src/repository.ts
index f1e7f369b..652521fe3 100644
--- a/src/repository.ts
+++ b/src/repository.ts
@@ -6,6 +6,14 @@ export interface RepositoryNwo {
   repo: string;
 }
 
+/** An approximation of what a repository NWO string looks like. */
+export type RepositoryNwoStr = `${string}/${string}`;
+
+/** A basic check that `val` looks like a `RepositoryNwoStr`. */
+export function isRepositoryNwoStr(val: string): val is RepositoryNwoStr {
+  return val.includes("/");
+}
+
 /**
  * Get the repository name with owner from the environment variable
  * `GITHUB_REPOSITORY`.
diff --git a/src/setup/repository.ts b/src/setup/repository.ts
index e2c370f88..2f68abd30 100644
--- a/src/setup/repository.ts
+++ b/src/setup/repository.ts
@@ -3,6 +3,7 @@ import { isRunningLocalAction } from "../actions-util";
 import * as api from "../api-client";
 import { ActionsEnvVars } from "../environment";
 import { GITHUB_DOTCOM_URL } from "../github";
+import { isRepositoryNwoStr, type RepositoryNwoStr } from "../repository";
 
 /** The NWO of the standard CodeQL Action repository. */
 export const CODEQL_DEFAULT_ACTION_REPOSITORY = "github/codeql-action";
@@ -17,7 +18,7 @@ export const CODEQL_DEFAULT_ACTION_REPOSITORY = "github/codeql-action";
  */
 export function getCodeQLActionRepository(
   action: ActionState<["ReadOnlyEnv", "Logger"]>,
-): string {
+): RepositoryNwoStr {
   if (isRunningLocalAction(action.env)) {
     // This handles the case where the Action does not come from an Action repository,
     // e.g. our integration tests which use the Action code from the current checkout.
@@ -28,11 +29,21 @@ export function getCodeQLActionRepository(
     return CODEQL_DEFAULT_ACTION_REPOSITORY;
   }
 
-  return action.env.getRequired(ActionsEnvVars.GITHUB_ACTION_REPOSITORY);
+  const actionRepository = action.env.getRequired(
+    ActionsEnvVars.GITHUB_ACTION_REPOSITORY,
+  );
+
+  if (isRepositoryNwoStr(actionRepository)) {
+    return actionRepository;
+  }
+
+  throw new Error(
+    `The value of '${ActionsEnvVars.GITHUB_ACTION_REPOSITORY}' is '${actionRepository}', which does not match the expected 'owner/repo' format.`,
+  );
 }
 
 /**A download source is a pair of strings. */
-export type DownloadSource = [string, string];
+export type DownloadSource = [string, RepositoryNwoStr];
 
 /** GitHub.com, and the canonical Action. */
 export const DEFAULT_DOWNLOAD_SOURCE: DownloadSource = [
@@ -77,7 +88,7 @@ export async function getCodeQLAssetDownloadURL(
 ): Promise<DownloadURL> {
   const codeQLActionRepository = getCodeQLActionRepository(action);
 
-  const potentialDownloadSources: Array<[string, string]> = [
+  const potentialDownloadSources: Array<[string, RepositoryNwoStr]> = [
     // This GitHub instance, and this Action.
     [apiDetails.url, codeQLActionRepository],
     // This GitHub instance, and the canonical Action.