chore: changeset validating github action (#1500)

* chore: changeset validating github action

* test: Create metal-birds-share.md

* style: lint

---------

Co-authored-by: Steven Spriggs <[email protected]>

.changeset/metal-birds-share.md

@@ -0,0 +1,5 @@
+---
+"@rhds/elements": major
+---
+DELETE THIS FILE BEFORE MERGING
+chore: changeset validating github action

.github/workflows/validate-pr.yml

@@ -0,0 +1,25 @@
+name: Validate PRs
+
+on:
+  pull_request:
+    types:
+      - opened
+      - reopened
+      - synchronize
+      - edited
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+      - run: npm i semantic-release @changesets/read --prefer-offline
+      - uses: actions/github-script@v7
+        with:
+          script: |
+            const { validate } = await import('${{ github.workspace }}/scripts/validate-prs.js');
+            await validate({ context });

scripts/validate-prs.js

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+import { default as read } from '@changesets/read';
+import semanticRelease from 'semantic-release';
+
+/** @typedef {'major'|'minor'|'patch'} ReleaseType */
+
+/**
+ * named capture group 1 `commitType`:
+ * > Either `feat`, `fix`, `chore`, `docs`, or `style`
+ * **ANY** (_>= 0x_)
+ * named capture group 2 `bang`:
+ * > `!`
+ */
+const COMMIT_TYPE_RE = /(?<commitType>feat|fix|chore|docs|style).*(?<bang>!)/;
+
+async function getReleaseType(title, mergeType) {
+  if (mergeType === 'rebase') {
+    const result = await semanticRelease({
+      dryRun: true,
+      branches: ['main'],
+    }) ?? {};
+    /** @type {ReleaseType} */
+    const type = result?.nextRelease?.type;
+    return type;
+  } else {
+    const { commitType, bang } = title.match(COMMIT_TYPE_RE)?.groups ?? {};
+    if (bang) {
+      return 'major';
+    } else {
+      switch (commitType) {
+        case 'feat': return 'minor';
+        case 'fix': return 'patch';
+      }
+    }
+  }
+}
+
+export async function validate({ context }) {
+  const { base, title, auto_merge: autoMerge } = context.payload.pull_request;
+
+  if (base.ref.startsWith('staging/')) {
+    return true;
+  }
+
+  const type = await getReleaseType(title, autoMerge?.merge_method) ?? null;
+  const sets = await read(process.cwd());
+
+  /** @type {ReleaseType} */
+  const release = sets.reduce((greatest, type) => {
+    switch (greatest) {
+      case null:
+      case 'major':
+        return greatest;
+      case 'minor':
+        return type === 'major' ? type : greatest;
+      case 'patch':
+        return (type === 'major' || type === 'minor') ? type : greatest;
+    }
+  }, null);
+
+  if (!release && type?.match(/m(aj|in)or/)) {
+    throw new Error(`PR conventional commit title has type (${type}) but no changesets were detected.`);
+  }
+
+  if (type !== release) {
+    throw new Error(`PR conventional commit title type (${type}) does not match release type (${release}).`);
+  }
+}