share changelog split, simplify getFileChanges return

processChangelog walks the changelog content once, sharing extractEntry
with readChangelogEntry so the entry-extraction loop isn't duplicated.

getFileChanges no longer returns its input file unchanged; the 2-tuple
matches what callers actually use.

Co-Authored-By: Claude (Opus 4.7) <noreply@anthropic.com>

Author: silverwind

index.test.ts

@@ -1408,15 +1408,15 @@ test("readVersionFromPyprojectToml returns null", () => withTmpDir(async (tmpDir
 test("getFileChanges package.json", () => withTmpDir(async (tmpDir) => {
   const file = join(tmpDir, "package.json");
   await writeFile(file, JSON.stringify({name: "test", version: "1.0.0"}, null, 2));
-  const [, content] = getFileChanges({file, baseVersion: "1.0.0", newVersion: "1.0.1"});
+  const [content] = getFileChanges({file, baseVersion: "1.0.0", newVersion: "1.0.1"});
   expect(JSON.parse(content!).version).toEqual("1.0.1");
 }));
 
 test("getFileChanges package-lock.json", () => withTmpDir(async (tmpDir) => {
   const file = join(tmpDir, "package-lock.json");
   const data = {name: "test", version: "1.0.0", lockfileVersion: 3, packages: {"": {version: "1.0.0"}}};
   await writeFile(file, JSON.stringify(data, null, 2));
-  const [, content] = getFileChanges({file, baseVersion: "1.0.0", newVersion: "2.0.0"});
+  const [content] = getFileChanges({file, baseVersion: "1.0.0", newVersion: "2.0.0"});
   const result = JSON.parse(content!);
   expect(result.version).toEqual("2.0.0");
   expect(result.packages[""].version).toEqual("2.0.0");
@@ -1425,43 +1425,43 @@ test("getFileChanges package-lock.json", () => withTmpDir(async (tmpDir) => {
 test("getFileChanges pyproject.toml", () => withTmpDir(async (tmpDir) => {
   const file = join(tmpDir, "pyproject.toml");
   await writeFile(file, `[project]\nname = "test"\nversion = "1.0.0"\n`);
-  const [, content] = getFileChanges({file, baseVersion: "1.0.0", newVersion: "1.1.0"});
+  const [content] = getFileChanges({file, baseVersion: "1.0.0", newVersion: "1.1.0"});
   expect(content).toContain(`version = "1.1.0"`);
 }));
 
 test("getFileChanges uv.lock", () => withTmpDir(async (tmpDir) => {
   await writeFile(join(tmpDir, "pyproject.toml"), `[project]\nname = "myapp"\nversion = "1.0.0"\n`);
   const file = join(tmpDir, "uv.lock");
   await writeFile(file, `[[package]]\nname = "myapp"\nversion = "1.0.0"\n`);
-  const [, content] = getFileChanges({file, baseVersion: "1.0.0", newVersion: "1.1.0"});
+  const [content] = getFileChanges({file, baseVersion: "1.0.0", newVersion: "1.1.0"});
   expect(content).toContain(`version = "1.1.0"`);
 }));
 
 test("getFileChanges generic file", () => withTmpDir(async (tmpDir) => {
   const file = join(tmpDir, "version.txt");
   await writeFile(file, "version 1.0.0 here");
-  const [, content] = getFileChanges({file, baseVersion: "1.0.0", newVersion: "2.0.0"});
+  const [content] = getFileChanges({file, baseVersion: "1.0.0", newVersion: "2.0.0"});
   expect(content).toEqual("version 2.0.0 here");
 }));
 
 test("getFileChanges lockfile skip", () => withTmpDir(async (tmpDir) => {
   const file = join(tmpDir, "yarn.lock");
   await writeFile(file, "content 1.0.0");
-  const [, content] = getFileChanges({file, baseVersion: "1.0.0", newVersion: "2.0.0"});
+  const [content] = getFileChanges({file, baseVersion: "1.0.0", newVersion: "2.0.0"});
   expect(content).toBeNull();
 }));
 
 test("getFileChanges with date", () => withTmpDir(async (tmpDir) => {
   const file = join(tmpDir, "changelog.txt");
   await writeFile(file, "version 1.0.0 released 2020-01-01");
-  const [, content] = getFileChanges({file, baseVersion: "1.0.0", newVersion: "1.0.1", date: "2025-06-15"});
+  const [content] = getFileChanges({file, baseVersion: "1.0.0", newVersion: "1.0.1", date: "2025-06-15"});
   expect(content).toEqual("version 1.0.1 released 2025-06-15");
 }));
 
 test("getFileChanges with replacements", () => withTmpDir(async (tmpDir) => {
   const file = join(tmpDir, "file.txt");
   await writeFile(file, "version 1.0.0 FOO");
-  const [, content] = getFileChanges({
+  const [content] = getFileChanges({
     file, baseVersion: "1.0.0", newVersion: "1.0.1",
     replacements: [{re: /FOO/, replacement: "BAR"}],
   });

index.ts

@@ -109,13 +109,7 @@ function findVersionHeading(lines: string[], version: string): {index: number, l
   return null;
 }
 
-// Lenient about heading shape: matches "# 1.2.3", "## v1.2.3", "## [1.2.3]",
-// "## [1.2.3] - 2024-01-15", "## 1.2.3 (2024-01-15)", etc.
-export function readChangelogEntry(content: string, version: string): string | null {
-  const lines = content.split(reNewline);
-  const head = findVersionHeading(lines, version);
-  if (!head) return null;
-
+function extractEntry(lines: string[], head: {index: number, level: number}): string | null {
   let end = lines.length;
   for (let i = head.index + 1; i < lines.length; i++) {
     const m = reHeading.exec(lines[i]);
@@ -124,26 +118,46 @@ export function readChangelogEntry(content: string, version: string): string | n
       break;
     }
   }
-
   return lines.slice(head.index + 1, end).join("\n").trim() || null;
 }
 
-export function updateChangelogHeadingDate(content: string, version: string, date: string): string | null {
-  const lines = content.split(reNewline);
-  const head = findVersionHeading(lines, version);
-  if (!head) return null;
-
-  const heading = lines[head.index];
+function updateHeadingDateInLines(lines: string[], index: number, date: string): string | null {
+  const heading = lines[index];
   if (rePlaceholderDate.test(heading)) {
-    lines[head.index] = heading.replace(rePlaceholderDate, date);
+    lines[index] = heading.replace(rePlaceholderDate, date);
   } else if (reDate.test(heading)) {
     return null;
   } else {
-    lines[head.index] = `${heading.trimEnd()} - ${date}`;
+    lines[index] = `${heading.trimEnd()} - ${date}`;
   }
   return lines.join("\n");
 }
 
+// Lenient about heading shape: matches "# 1.2.3", "## v1.2.3", "## [1.2.3]",
+// "## [1.2.3] - 2024-01-15", "## 1.2.3 (2024-01-15)", etc.
+export function readChangelogEntry(content: string, version: string): string | null {
+  const lines = content.split(reNewline);
+  const head = findVersionHeading(lines, version);
+  if (!head) return null;
+  return extractEntry(lines, head);
+}
+
+export function updateChangelogHeadingDate(content: string, version: string, date: string): string | null {
+  const lines = content.split(reNewline);
+  const head = findVersionHeading(lines, version);
+  if (!head) return null;
+  return updateHeadingDateInLines(lines, head.index, date);
+}
+
+function processChangelog(content: string, version: string, date: string): {entry: string, updated: string | null} | null {
+  const lines = content.split(reNewline);
+  const head = findVersionHeading(lines, version);
+  if (!head) return null;
+  const entry = extractEntry(lines, head);
+  if (!entry) return null;
+  return {entry, updated: updateHeadingDateInLines(lines, head.index, date)};
+}
+
 export async function removeIgnoredFiles(files: Array<string>, cwd?: string): Promise<Array<string>> {
   let result: Result;
   try {
@@ -163,12 +177,12 @@ export type GetFileChangesOpts = {
   date?: string,
 };
 
-export function getFileChanges({file, baseVersion, newVersion, replacements, date}: GetFileChangesOpts): [string, string | null, string | null] {
+export function getFileChanges({file, baseVersion, newVersion, replacements, date}: GetFileChangesOpts): [string | null, string | null] {
   const fileName = basename(file);
 
   // unhandled lockfiles: blind search-and-replace would corrupt dependency versions
   if ((/lock/i.test(fileName) || fileName === "go.sum") && fileName !== "package-lock.json" && fileName !== "uv.lock") {
-    return [file, null, null];
+    return [null, null];
   }
 
   const oldData = readFileSync(file, "utf8");
@@ -207,7 +221,7 @@ export function getFileChanges({file, baseVersion, newVersion, replacements, dat
     }
   }
 
-  return [file, newData, oldData];
+  return [newData, oldData];
 }
 
 export function write(file: string, content: string): void {
@@ -600,9 +614,9 @@ async function main(): Promise<void> {
     } catch {
       return null;
     }
-    const entry = readChangelogEntry(original, newVersion);
-    if (!entry) return null;
-    return {path, entry, original, updated: updateChangelogHeadingDate(original, newVersion, today)};
+    const processed = processChangelog(original, newVersion, today);
+    if (!processed) return null;
+    return {path, original, entry: processed.entry, updated: processed.updated};
   })();
 
   const allFiles = changelogInfo?.updated ? [...files, relative(pwd, changelogInfo.path)] : files;
@@ -659,11 +673,11 @@ async function main(): Promise<void> {
       for (const [file, content] of originals) write(file, content);
     });
     for (const file of files) {
-      const [filePath, newData, oldData] = getFileChanges({file, baseVersion, newVersion, replacements, date});
+      const [newData, oldData] = getFileChanges({file, baseVersion, newVersion, replacements, date});
       if (newData !== null) {
-        if (!originals.has(filePath)) originals.set(filePath, oldData!);
-        logVerbose(`writing ${filePath}`);
-        write(filePath, newData);
+        if (!originals.has(file)) originals.set(file, oldData!);
+        logVerbose(`writing ${file}`);
+        write(file, newData);
       } else {
         logVerbose(`skipping ${file} (unhandled lockfile)`);
       }