Simplify getHeader to operate on ChangelogSections

pr-checks/changelog.test.ts

@@ -26,20 +26,26 @@ import { CHANGELOG_FILE } from "./config";
 const testDate = new Date(2026, 7, 14);
 
 describe("getHeader", async () => {
+  function Section(headerLine: string): ChangelogSection {
+    return {
+      headerLine,
+      bodyLines: [],
+    };
+  }
   await it("returns non-headers unchanged", () => {
-    assert.equal("foo", getHeader("foo"));
-    assert.equal("- bar", getHeader("- bar"));
+    assert.equal("foo", getHeader(Section("foo")));
+    assert.equal("- bar", getHeader(Section("- bar")));
   });
   await it("strips octothorpes", async () => {
-    assert.equal("foo", getHeader("# foo"));
-    assert.equal("foo", getHeader("## foo"));
-    assert.equal("foo", getHeader("### foo"));
-    assert.equal("foo", getHeader("#### foo"));
-    assert.equal("foo", getHeader("##### foo"));
-    assert.equal("foo", getHeader("###### foo"));
+    assert.equal("foo", getHeader(Section("# foo")));
+    assert.equal("foo", getHeader(Section("## foo")));
+    assert.equal("foo", getHeader(Section("### foo")));
+    assert.equal("foo", getHeader(Section("#### foo")));
+    assert.equal("foo", getHeader(Section("##### foo")));
+    assert.equal("foo", getHeader(Section("###### foo")));
   });
   await it("strips whitespace", async () => {
-    assert.equal("foo", getHeader("# foo  "));
+    assert.equal("foo", getHeader(Section("# foo  ")));
   });
 });
 

pr-checks/changelog.ts

@@ -33,9 +33,11 @@ export interface Changelog {
   sections: ChangelogSection[];
 }
 
-/** Returns the text of a CHANGELOG.md header (without the '## ' prefix). */
-export function getHeader(headerLine: string): string {
-  return headerLine.replace(/^#+\s+/, "").trimEnd();
+/**
+ * Returns the text of the header (without the '## ' prefix) of the given section.
+ * */
+export function getHeader(section: ChangelogSection): string {
+  return section.headerLine.replace(/^#+\s+/, "").trimEnd();
 }
 
 /** Returns `date` formatted as `DD Mon YYYY`. */
@@ -147,7 +149,7 @@ export function addBodyLinesToUnreleasedSection(
   lines: string[],
 ) {
   const unreleasedSection = changelog.sections[0];
-  if (getHeader(unreleasedSection.headerLine) !== UNRELEASED_PLACEHOLDER) {
+  if (getHeader(unreleasedSection) !== UNRELEASED_PLACEHOLDER) {
     throw Error("'[UNRELEASED]' is not the first section of 'CHANGELOG.md'");
   }