Simplify addBodyLinesToUnreleasedSection

pr-checks/changelog.test.ts

@@ -108,25 +108,20 @@ describe("addBodyLinesToUnreleasedSection", async () => {
     };
   }
 
-  await it("throws error if '[UNRELEASED]' section does not exist", async () => {
-    const emptyChangelog = newChangelogWithSections([]);
-    assert.throws(() => addBodyLinesToUnreleasedSection(emptyChangelog, []));
-
-    const releasedChangelog = newChangelogWithSections([
+  await it("throws error if '[UNRELEASED]' section is not first", async () => {
+    const invalidChangelog = newChangelogWithSections([
       {
         headerLine: "## Release 1.0.0",
         bodyLines: [],
       },
       {
-        headerLine: "## Release 2.0.0",
-        bodyLines: [],
-      },
-      {
-        headerLine: "## Release 3.0.0",
+        headerLine: `## ${UNRELEASED_PLACEHOLDER}`,
         bodyLines: [],
       },
     ]);
-    assert.throws(() => addBodyLinesToUnreleasedSection(releasedChangelog, []));
+    assert.throws(() =>
+      addBodyLinesToUnreleasedSection(invalidChangelog, ["foo"]),
+    );
   });
 
   await it("overwrites 'No user facing changes.'", async () => {

pr-checks/changelog.ts

@@ -148,32 +148,21 @@ export function addBodyLinesToUnreleasedSection(
   changelog: Changelog,
   lines: string[],
 ) {
+  // Do nothing if there is nothing to insert.
+  if (lines.length === 0) return;
+
   const unreleasedSection = changelog.sections[0];
   if (getHeader(unreleasedSection) !== UNRELEASED_PLACEHOLDER) {
     throw Error("'[UNRELEASED]' is not the first section of 'CHANGELOG.md'");
   }
 
-  let insertAtIndex = 0;
-  let deleteCount = 0;
-
-  // If the section contains an empty line, preserve it -- insert afterward.
-  if (
-    unreleasedSection.bodyLines.length > 0 &&
-    unreleasedSection.bodyLines[0] === ""
-  ) {
-    insertAtIndex++;
+  if (unreleasedSection.bodyLines.includes(NO_CHANGES_STR)) {
+    unreleasedSection.bodyLines = ["", ...lines, ""];
+    return;
   }
 
-  // If the section contains the stock message 'No user facing changes.'
-  if (
-    lines.length > 0 &&
-    unreleasedSection.bodyLines.length > insertAtIndex &&
-    unreleasedSection.bodyLines[insertAtIndex].trim() === NO_CHANGES_STR
-  ) {
-    deleteCount++; // Delete the line by incrementing the delete marker.
-  }
-
-  unreleasedSection.bodyLines.splice(insertAtIndex, deleteCount, ...lines);
+  // Insert `lines` after the first blank line.
+  unreleasedSection.bodyLines.splice(1, 0, ...lines);
 }
 
 /**