ci: use @changesets/get-release-plan (#358)

* WIP: use @changesets/get-release-plan

* Tweak reason

* Add colours

* Don't double log

* Sort by name only

* Update sorting

* Fix spacing

* Undo temp changes

* Update description

Author: lachlancollins

.github/changeset-preview/action.yml

@@ -3,6 +3,10 @@ description: Generates comment on a PR showing expected version impact
 runs:
   using: composite
   steps:
+    - name: Install dependencies
+      shell: bash
+      run: npm install
+      working-directory: ${{ github.action_path }}
     - name: Preview version bumps
       shell: bash
       run: node ${{ github.action_path }}/preview-changeset-versions.mjs --output /tmp/changeset-preview.md

.github/changeset-preview/package.json

@@ -0,0 +1,5 @@
+{
+  "dependencies": {
+    "@changesets/get-release-plan": "^4.0.15"
+  }
+}

.github/changeset-preview/preview-changeset-versions.mjs

@@ -1,81 +1,21 @@
 #!/usr/bin/env node
 
 /**
- * Preview the version bumps that `changeset version` will produce.
- *
- * Workflow:
- *   1. Snapshot every workspace package's current version
- *   2. Run `changeset version` (mutates package.json files)
- *   3. Diff against the snapshot
- *   4. Print a markdown summary (or write to --output file)
- *
- * This script is meant to run in CI on a disposable checkout — it does NOT
- * revert the changes it makes.
+ * Uses `@changesets/get-release-plan` to get the version bumps and formats it as markdown.
  */
 
-import { execSync } from 'node:child_process'
-import { readdirSync, readFileSync, writeFileSync } from 'node:fs'
-import { join, resolve } from 'node:path'
+import { writeFileSync } from 'node:fs'
+import { resolve } from 'node:path'
 import { parseArgs } from 'node:util'
+import getReleasePlan from '@changesets/get-release-plan'
 
 const ROOT = resolve(import.meta.dirname, '..', '..')
 
-const PACKAGES_DIR = join(ROOT, 'packages')
-
-function readPackageVersions() {
-  const versions = new Map()
-  for (const dir of readdirSync(PACKAGES_DIR, { withFileTypes: true })) {
-    if (!dir.isDirectory()) continue
-    const pkgPath = join(PACKAGES_DIR, dir.name, 'package.json')
-    try {
-      const pkg = JSON.parse(readFileSync(pkgPath, 'utf8'))
-      if (pkg.name && pkg.version && pkg.private !== true) {
-        versions.set(pkg.name, pkg.version)
-      }
-    } catch {
-      // skip packages without a valid package.json
-    }
-  }
-  return versions
+function reasonRank(reason) {
+  return reason === 'Changeset' ? 2 : 1
 }
 
-function readChangesetEntries() {
-  const changesetDir = join(ROOT, '.changeset')
-  const explicit = new Map()
-  for (const file of readdirSync(changesetDir)) {
-    if (file === 'config.json' || file === 'README.md' || !file.endsWith('.md'))
-      continue
-    const content = readFileSync(join(changesetDir, file), 'utf8')
-    const frontmatterMatch = content.match(/^---\n([\s\S]*?)\n---/)
-    if (!frontmatterMatch) continue
-    for (const line of frontmatterMatch[1].split('\n')) {
-      const match = line.match(/^['"]?([^'"]+)['"]?\s*:\s*(major|minor|patch)/)
-      if (match) {
-        const [, name, bump] = match
-        const existing = explicit.get(name)
-        // keep the highest bump if a package appears in multiple changesets
-        if (!existing || bumpRank(bump) > bumpRank(existing)) {
-          explicit.set(name, bump)
-        }
-      }
-    }
-  }
-  return explicit
-}
-
-function bumpRank(bump) {
-  return bump === 'major' ? 3 : bump === 'minor' ? 2 : 1
-}
-
-function bumpType(oldVersion, newVersion) {
-  const [oMaj, oMin] = oldVersion.split('.').map(Number)
-  const [nMaj, nMin] = newVersion.split('.').map(Number)
-  if (nMaj > oMaj) return 'major'
-  if (nMin > oMin) return 'minor'
-  return 'patch'
-}
-
-function main() {
+async function main() {
   const { values } = parseArgs({
     args: process.argv.slice(2),
     options: {
@@ -85,10 +25,10 @@ function main() {
     allowPositionals: false,
   })
 
-  // 1. Read explicit changeset entries
-  const explicit = readChangesetEntries()
+  const releasePlan = await getReleasePlan(ROOT)
+  const releases = releasePlan.releases
 
-  if (explicit.size === 0) {
+  if (releases.length === 0) {
     const msg =
       'No changeset entries found. Merging this PR will not cause a version bump for any packages.\n'
     process.stdout.write(msg)
@@ -99,42 +39,19 @@ function main() {
     return
   }
 
-  // 2. Snapshot current versions
-  const before = readPackageVersions()
-
-  // 3. Temporarily swap changeset config to skip changelog generation
-  //    (the GitHub changelog plugin requires a token we don't need for previews)
-  const configPath = join(ROOT, '.changeset', 'config.json')
-  const originalConfig = readFileSync(configPath, 'utf8')
-  try {
-    const config = JSON.parse(originalConfig)
-    config.changelog = false
-    writeFileSync(configPath, JSON.stringify(config, null, 2))
-
-    // 4. Run changeset version
-    execSync('pnpm changeset version', { cwd: ROOT, stdio: 'pipe' })
-  } finally {
-    // Always restore the original config
-    writeFileSync(configPath, originalConfig)
-  }
-
-  // 5. Read new versions
-  const after = readPackageVersions()
-
   // 6. Diff
   const bumps = []
-  for (const [name, newVersion] of after) {
-    const oldVersion = before.get(name)
-    if (!oldVersion || oldVersion === newVersion) continue
-    const bump = bumpType(oldVersion, newVersion)
-    const source = explicit.has(name) ? explicit.get(name) : 'dependency'
-    bumps.push({ name, oldVersion, newVersion, bump, source })
+  for (const release of releases) {
+    if (release.oldVersion === release.newVersion) continue
+    const reason = release.changesets.length !== 0 ? 'Changeset' : 'Dependent'
+    bumps.push({ ...release, reason })
   }
 
-  // Sort: major first, then minor, then patch; within each group alphabetical
+  // Order by reason and name
   bumps.sort(
     (a, b) =>
-      bumpRank(b.bump) - bumpRank(a.bump) || a.name.localeCompare(b.name),
+      reasonRank(b.reason) - reasonRank(a.reason) ||
+      a.name.localeCompare(b.name),
   )
 
   // 7. Build markdown
@@ -145,41 +62,53 @@ function main() {
       'No version changes detected. Merging this PR will not cause a version bump for any packages.',
     )
   } else {
-    const explicitBumps = bumps.filter((b) => b.source !== 'dependency')
-    const dependencyBumps = bumps.filter((b) => b.source === 'dependency')
+    const majorBumps = bumps.filter((b) => b.type === 'major')
+    const minorBumps = bumps.filter((b) => b.type === 'minor')
+    const patchBumps = bumps.filter((b) => b.type === 'patch')
+    const directBumps = bumps.filter((b) => b.reason === 'Changeset')
+    const indirectBumps = bumps.filter((b) => b.reason === 'Dependent')
 
     lines.push(
-      `**${explicitBumps.length}** package(s) bumped directly, **${dependencyBumps.length}** bumped as dependents.`,
+      `**${directBumps.length}** package(s) bumped directly, **${indirectBumps.length}** bumped as dependents.`,
     )
     lines.push('')
 
-    if (explicitBumps.length > 0) {
-      lines.push('### Direct bumps')
+    if (majorBumps.length > 0) {
+      lines.push('### 🟥 Major bumps')
+      lines.push('')
+      lines.push('| Package | Version | Reason |')
+      lines.push('| --- | --- | --- |')
+      for (const b of majorBumps) {
+        lines.push(
+          `| \`${b.name}\` | ${b.oldVersion} → ${b.newVersion} | ${b.reason} |`,
+        )
+      }
+      lines.push('')
+    }
+
+    if (minorBumps.length > 0) {
+      lines.push('### 🟨 Minor bumps')
       lines.push('')
-      lines.push('| Package | Bump | Version |')
+      lines.push('| Package | Version | Reason |')
       lines.push('| --- | --- | --- |')
-      for (const b of explicitBumps) {
+      for (const b of minorBumps) {
         lines.push(
-          `| \`${b.name}\` | **${b.bump}** | ${b.oldVersion} → ${b.newVersion} |`,
+          `| \`${b.name}\` | ${b.oldVersion} → ${b.newVersion} | ${b.reason} |`,
         )
       }
       lines.push('')
     }
 
-    if (dependencyBumps.length > 0) {
-      lines.push(
-        '<details>',
-        `<summary>Dependency bumps (${dependencyBumps.length})</summary>`,
-        '',
-        '| Package | Bump | Version |',
-        '| --- | --- | --- |',
-      )
-      for (const b of dependencyBumps) {
+    if (patchBumps.length > 0) {
+      lines.push('### 🟩 Patch bumps')
+      lines.push('')
+      lines.push('| Package | Version | Reason |')
+      lines.push('| --- | --- | --- |')
+      for (const b of patchBumps) {
         lines.push(
-          `| \`${b.name}\` | ${b.bump} | ${b.oldVersion} → ${b.newVersion} |`,
+          `| \`${b.name}\` | ${b.oldVersion} → ${b.newVersion} | ${b.reason} |`,
         )
       }
-      lines.push('', '</details>')
     }
   }
 

.github/changeset-preview/upsert-pr-comment.mjs

@@ -111,8 +111,6 @@ async function main() {
   const rawBody = await fsp.readFile(bodyPath, 'utf8')
   const body = `${args.marker}\n## 🚀 Changeset Version Preview\n\n${rawBody}`
 
-  process.stdout.write(body)
-
   const comments = await listIssueComments({
     apiUrl: args.apiUrl,
     token: args.token,