fix: preserve frontmatter when updating changelog

lib/lifecycles/changelog.js

@@ -18,17 +18,38 @@ Changelog.START_OF_LAST_RELEASE_PATTERN = START_OF_LAST_RELEASE_PATTERN
 
 module.exports = Changelog
 
+/**
+ * Front matter is only extracted and therefore retained in final output where Changelog "header" begins with #Changelog,
+ * e.g. meets Standard-Version (last release) or commit-and-tag-version(current) format
+ */
+function extractFrontMatter (oldContent) {
+  const headerStart = oldContent.indexOf('# Changelog')
+  return headerStart !== -1 || headerStart !== 0
+    ? oldContent.substring(0, headerStart)
+    : ''
+}
+
+/**
+ * find the position of the last release and remove header
+ */
+function extractChangelogBody (oldContent) {
+  const oldContentStart = oldContent.search(START_OF_LAST_RELEASE_PATTERN)
+  return oldContentStart !== -1
+    ? oldContent.substring(oldContentStart)
+    : oldContent
+}
+
 function outputChangelog (args, newVersion) {
   return new Promise((resolve, reject) => {
     createIfMissing(args)
     const header = args.header
 
-    let oldContent = args.dryRun || args.releaseCount === 0 ? '' : fs.readFileSync(args.infile, 'utf-8')
-    const oldContentStart = oldContent.search(START_OF_LAST_RELEASE_PATTERN)
-    // find the position of the last release and remove header:
-    if (oldContentStart !== -1) {
-      oldContent = oldContent.substring(oldContentStart)
-    }
+    const oldContent = args.dryRun || args.releaseCount === 0 ? '' : fs.readFileSync(args.infile, 'utf-8')
+
+    const oldContentBody = extractChangelogBody(oldContent)
+
+    const changelogFrontMatter = extractFrontMatter(oldContent)
+
     let content = ''
     const context = { version: newVersion }
     const changelogStream = conventionalChangelog({
@@ -48,7 +69,7 @@ function outputChangelog (args, newVersion) {
     changelogStream.on('end', function () {
       checkpoint(args, 'outputting changes to %s', [args.infile])
       if (args.dryRun) console.info(`\n---\n${chalk.gray(content.trim())}\n---\n`)
-      else writeFile(args, args.infile, header + '\n' + (content + oldContent).replace(/\n+$/, '\n'))
+      else writeFile(args, args.infile, changelogFrontMatter + header + '\n' + (content + oldContentBody).replace(/\n+$/, '\n'))
       return resolve()
     })
   })

test/core.spec.js

@@ -165,17 +165,73 @@ describe('cli', function () {
   })
 
   describe('CHANGELOG.md exists', function () {
-    it('appends the new release above the last release, removing the old header (legacy format)', async function () {
+    it('appends the new release above the last release, removing the old header (legacy format), and does not retain any front matter', async function () {
+      const frontMatter =
+          '---\nstatus: new\n---\n'
       mock({
         bump: 'patch',
         changelog: 'release 1.0.1\n',
-        fs: { 'CHANGELOG.md': 'legacy header format<a name="1.0.0">\n' },
+        fs: { 'CHANGELOG.md': frontMatter + 'legacy header format<a name="1.0.0">\n' },
         tags: ['v1.0.0']
       })
       await exec()
       const content = fs.readFileSync('CHANGELOG.md', 'utf-8')
       content.should.match(/1\.0\.1/)
       content.should.not.match(/legacy header format/)
+      content.should.not.match(/---status: new---/)
+    })
+
+    it('appends the new release above the last release, replacing the old header (standard-version format) with header (new format), and retains any front matter', async function () {
+      const { header } = require('../defaults')
+
+      const standardVersionHeader =
+          '# Changelog\n\nAll notable changes to this project will be documented in this file. See [standard-version](https://github.com/conventional-changelog/standard-version) for commit guidelines.'
+
+      const frontMatter =
+          '---\nstatus: new\n---\n'
+
+      const changelog101 =
+          '### [1.0.1](/compare/v1.0.0...v1.0.1) (YYYY-MM-DD)\n\n\n### Bug Fixes\n\n* patch release ABCDEFXY\n'
+
+      const changelog100 =
+          '### [1.0.0](/compare/v0.0.1...v1.0.0) (YYYY-MM-DD)\n\n\n### Features\n\n* Version one feature set\n'
+
+      const initialChangelog = frontMatter + '\n' + standardVersionHeader + '\n' + changelog100
+
+      mock({
+        bump: 'patch',
+        changelog: changelog101,
+        fs: { 'CHANGELOG.md': initialChangelog },
+        tags: ['v1.0.0']
+      })
+      await exec()
+      const content = fs.readFileSync('CHANGELOG.md', 'utf-8')
+      content.should.equal(frontMatter + '\n' + header + '\n' + changelog101 + changelog100)
+    })
+
+    it('appends the new release above the last release, removing the old header (new format), and retains any front matter', async function () {
+      const { header } = require('../defaults')
+      const frontMatter =
+          '---\nstatus: new\n---\n'
+
+      const changelog101 =
+          '### [1.0.1](/compare/v1.0.0...v1.0.1) (YYYY-MM-DD)\n\n\n### Bug Fixes\n\n* patch release ABCDEFXY\n'
+
+      const changelog100 =
+          '### [1.0.0](/compare/v0.0.1...v1.0.0) (YYYY-MM-DD)\n\n\n### Features\n\n* Version one feature set\n'
+
+      const initialChangelog = frontMatter + '\n' + header + '\n' + changelog100
+
+      mock({
+        bump: 'patch',
+        changelog: changelog101,
+        fs: { 'CHANGELOG.md': initialChangelog },
+        tags: ['v1.0.0']
+      })
+      await exec()
+
+      const content = fs.readFileSync('CHANGELOG.md', 'utf-8')
+      content.should.equal(frontMatter + '\n' + header + '\n' + changelog101 + changelog100)
     })
 
     it('appends the new release above the last release, removing the old header (new format)', async function () {