feat(github-actions): add stale draft PR action

.github/local-actions/stale-cleanup/BUILD.bazel

@@ -0,0 +1,32 @@
+load("@devinfra_npm//:defs.bzl", "npm_link_all_packages")
+load("//tools:defaults.bzl", "esbuild_checked_in", "ts_project")
+
+package(default_visibility = ["//.github/local-actions/stale-cleanup:__subpackages__"])
+
+npm_link_all_packages()
+
+ts_project(
+    name = "lib",
+    srcs = glob(
+        ["lib/*.ts"],
+    ),
+    tsconfig = "//.github/local-actions:tsconfig",
+    deps = [
+        "//.github/local-actions/stale-cleanup:node_modules/@actions/core",
+        "//.github/local-actions/stale-cleanup:node_modules/@actions/github",
+        "//.github/local-actions/stale-cleanup:node_modules/@octokit/rest",
+        "//.github/local-actions/stale-cleanup:node_modules/@types/node",
+        "//github-actions:utils",
+    ],
+)
+
+esbuild_checked_in(
+    name = "main",
+    srcs = [
+        ":lib",
+    ],
+    entry_point = "lib/main.ts",
+    format = "esm",
+    platform = "node",
+    target = "node24",
+)

.github/local-actions/stale-cleanup/action.yml

@@ -0,0 +1,15 @@
+name: 'Stale Draft PR Cleanup'
+description: 'Automatically closes draft PRs that have been inactive for a specific number of days.'
+author: 'Angular'
+inputs:
+  angular-robot-key:
+    description: 'The private key for the Angular Robot Github app.'
+    required: true
+  repos:
+    description: |
+      The repositories in which to clean up stale draft PRs. The organization name is derived from
+      the context in where the action runs.
+    required: true
+runs:
+  using: 'node24'
+  main: 'main.js'

.github/local-actions/stale-cleanup/lib/main.ts

@@ -0,0 +1,99 @@
+import * as core from '@actions/core';
+import {context} from '@actions/github';
+import {Octokit} from '@octokit/rest';
+import {
+  ANGULAR_ROBOT,
+  getAuthTokenFor,
+  revokeActiveInstallationToken,
+} from '../../../../github-actions/utils.js';
+
+const STALE_DAYS = 28;
+
+export async function closeStaleDraftPrs(github: Octokit, repo: string): Promise<void> {
+  const message = `This draft PR is being closed because it has been stale for ${STALE_DAYS} days and has seen no activity from you. If you'd like to see this change land, you can re-open this PR. Thank you for being an Angular contributor!`;
+
+  const threshold = new Date();
+  threshold.setDate(threshold.getDate() - STALE_DAYS);
+  const thresholdIso = threshold.toISOString();
+
+  const repositoryName = `${context.repo.owner}/${repo}`;
+  const query = `repo:${repositoryName} is:pr is:draft is:open updated:<${thresholdIso} sort:updated-asc`;
+  core.info('Stale Draft PR Query: ' + query);
+
+  let closeCount = 0;
+  // We look at 100 at a time to avoid handling too many PRs in one go.
+  // With each batch of 100 we'll eventually burn down the list of all stale draft PRs.
+  const prResponse = await github.search.issuesAndPullRequests({
+    q: query,
+    per_page: 100,
+  });
+
+  core.info(`Stale Draft PR Query found ${prResponse.data.total_count} items`);
+
+  if (!prResponse.data.items.length) {
+    core.info(`No draft PRs to close`);
+    return;
+  }
+
+  core.info(`Attempting to close up to ${prResponse.data.items.length} draft PR(s)`);
+  core.startGroup('Closing stale draft PRs');
+
+  for (const item of prResponse.data.items) {
+    if (!item.pull_request) continue;
+
+    try {
+      await github.request('POST /graphql', {
+        query: `
+          mutation CloseStalePR($id: ID!, $body: String!) {
+            addComment(input: {subjectId: $id, body: $body}) {
+              clientMutationId
+            }
+            closePullRequest(input: {pullRequestId: $id}) {
+              pullRequest {
+                state
+              }
+            }
+          }
+        `,
+        variables: {
+          id: item.node_id,
+          body: message,
+        },
+      });
+
+      ++closeCount;
+    } catch (error: unknown) {
+      const e = error as Error & {request?: unknown};
+      core.warning(`Unable to close draft PR ${repositoryName}#${item.number}: ${e.message}`);
+      if (typeof e.request === 'object') {
+        core.error(JSON.stringify(e.request, null, 2));
+      }
+    }
+  }
+
+  core.endGroup();
+  core.info(`Closed ${closeCount} stale draft PR(s)`);
+}
+
+async function main() {
+  const github = new Octokit({auth: await getAuthTokenFor(ANGULAR_ROBOT)});
+  try {
+    const repos = core.getMultilineInput('repos', {required: true, trimWhitespace: true});
+    await core.group('Repos being cleaned:', async () =>
+      repos.forEach((repo) => core.info(`- ${repo}`)),
+    );
+    for (const repo of repos) {
+      await closeStaleDraftPrs(github, repo);
+    }
+  } catch (error: any) {
+    core.debug(error.message);
+    core.setFailed(error.message);
+  } finally {
+    await revokeActiveInstallationToken(github);
+  }
+}
+
+main().catch((err) => {
+  console.error(err);
+  core.setFailed('Failed with the above error');
+});