chore: add bot to comment on PRs

.github/workflows/pull_request_labels.yaml

@@ -0,0 +1,25 @@
+name: Add labels to pull requests
+
+on:
+  pull_request_target:
+    types: [
+      opened,
+      reopened,
+      review_requested,
+    ]
+  pull_request_review:
+    types: [submitted, edited, dismissed]
+
+jobs:
+  pull_request_labels:
+    runs-on: ubuntu-22.04
+    if: github.repository == 'denoland/deno'
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Label pull request
+        uses: actions/github-script@v7
+        with:
+          script: |
+            require('./tools/label_pull_request.js')({ context, github })

tools/label_pull_request.js

@@ -0,0 +1,55 @@
+// Copyright 2018-2025 the Deno authors. MIT license.
+
+// deno-lint-ignore-file no-console camelcase
+
+async function createComment(context, github) {
+  await github.rest.issues.createComment({
+    issue_number: context.issue.number,
+    owner: context.repo.owner,
+    repo: context.repo.repo,
+    body: `Thanks for the PR!
+
+Once you are done, please request a review from a Deno team member.`,
+  });
+}
+
+async function updateLabels(context, github) {
+  const result = await github.rest.issues
+    .listLabelsOnIssue({
+      issue_number: context.payload.pull_request.number,
+      owner: context.repo.owner,
+      repo: context.repo.repo,
+    });
+  const labelNames = result.data.map((label) => label.name);
+  labelNames.push("pr:needs-review");
+
+  return github.rest.issues.setLabels({
+    issue_number: context.payload.pull_request.number,
+    owner: context.repo.owner,
+    repo: context.repo.repo,
+    labels: labelNames,
+  });
+}
+
+// TODO(bartlomieju): figure out how to use ES modules in GH Actions scripts
+module.exports = async ({ context, github }) => {
+  const eventHandlers = {
+    opened: createComment,
+    reopened: createComment,
+    review_requested: updateLabels,
+  };
+
+  const eventName = context.payload.action;
+  const eventHandler = eventHandlers[eventName];
+
+  if (!eventHandler) {
+    console.log(`::warning::'${eventName}' event has no handler, skipping.`);
+    return;
+  }
+
+  try {
+    await eventHandler(context, github);
+  } catch (error) {
+    console.log("::warning::Error, during update, bailing out: ", error);
+  }
+};