chore(ci): verify the PR title as part of linting (#18163)

This verifies the PR title as part of the lint step.

.github/workflows/ci.generate.ts

@@ -473,6 +473,12 @@ const ci = {
             run:
               "deno run --unstable --allow-write --allow-read --allow-run ./tools/format.js --check",
           },
+          {
+            name: "Lint PR title",
+            if: "matrix.job == 'lint' && github.event_name == 'pull_request'",
+            run:
+              "deno run ./tools/verify_pr_title.js '${{ github.event.pull_request.title }}'",
+          },
           {
             name: "lint.js",
             if: "matrix.job == 'lint'",

.github/workflows/ci.yml

@@ -285,6 +285,9 @@ jobs:
       - name: test_format.js
         if: '!(github.event_name == ''pull_request'' && matrix.skip_pr) && (steps.exit_early.outputs.EXIT_EARLY != ''true'' && (matrix.job == ''lint''))'
         run: deno run --unstable --allow-write --allow-read --allow-run ./tools/format.js --check
+      - name: Lint PR title
+        if: '!(github.event_name == ''pull_request'' && matrix.skip_pr) && (steps.exit_early.outputs.EXIT_EARLY != ''true'' && (matrix.job == ''lint'' && github.event_name == ''pull_request''))'
+        run: 'deno run ./tools/verify_pr_title.js ''${{ github.event.pull_request.title }}'''
       - name: lint.js
         if: '!(github.event_name == ''pull_request'' && matrix.skip_pr) && (steps.exit_early.outputs.EXIT_EARLY != ''true'' && (matrix.job == ''lint''))'
         run: deno run --unstable --allow-write --allow-read --allow-run ./tools/lint.js

tools/verify_pr_title.js

@@ -0,0 +1,47 @@
+// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
+const prTitle = Deno.args[0];
+
+if (prTitle == null) {
+  Deno.exit(0); // not a PR
+}
+
+console.log("PR title:", prTitle);
+
+// This is a release PR, so it's valid.
+if (/^[^\s]+\.[^\s]+\.[^\s]+$/.test(prTitle)) {
+  console.log("Valid.");
+  Deno.exit(0);
+}
+
+const validPrefixes = [
+  "chore",
+  "fix",
+  "feat",
+  "perf",
+  "ci",
+  "cleanup",
+  "docs",
+  "bench",
+  "build",
+  "refactor",
+  "test",
+  // allow Revert PRs because it allows us to remove the landed
+  // commit from the generated changelog
+  "Revert ",
+];
+
+if (validPrefixes.some((prefix) => prTitle.startsWith(prefix))) {
+  console.log("Valid.");
+} else {
+  console.error(
+    "The PR title must start with one of the following prefixes:\n",
+  );
+  for (const prefix of validPrefixes) {
+    console.error(`  - ${prefix}`);
+  }
+  console.error(
+    "\nPlease fix the PR title according to https://www.conventionalcommits.org " +
+      "then push an empty commit to reset the CI.",
+  );
+  Deno.exit(1);
+}