feat(github-actions): introduce action to identify PRs affecting Google

This is the external part to the internal service. The internal service
will complete the commit statuses for PRs needing internal presubmits.

This action exists as we do not auto-generate presubmits for PRs.

.prettierignore

@@ -5,6 +5,7 @@ ng-dev/utils/protos/*.js
 
 github-actions/create-pr-for-changes/main.js
 github-actions/feature-request/main.js
+github-actions/google-internal-tests/main.js
 github-actions/lock-closed/main.js
 github-actions/commit-message-based-labels/main.js
 github-actions/slash-commands/main.js

github-actions/google-internal-tests/BUILD.bazel

@@ -0,0 +1,12 @@
+load("//tools:defaults.bzl", "esbuild_checked_in")
+
+package(default_visibility = ["//github-actions/google-internal-tests:__subpackages__"])
+
+esbuild_checked_in(
+    name = "main",
+    entry_point = "//github-actions/google-internal-tests/lib:main.ts",
+    target = "node16",
+    deps = [
+        "//github-actions/google-internal-tests/lib",
+    ],
+)

github-actions/google-internal-tests/action.yml

@@ -0,0 +1,22 @@
+name: Google Internal Tests
+description: |
+  Action for identifying pull requests which require the execution of Google Internal
+  tests. For irrelevant PRs, a status check is added to indicate the irrelevance to G3.
+author: 'Angular'
+inputs:
+  github-token:
+    required: true
+    description: GitHub Token used for creating the commit statuses.
+  affected-file-patterns:
+    required: true
+    description: |
+      List of file patterns which match files synced into Google.
+      Multiple patterns should be separated by new lines.
+  run-tests-guide-url:
+    required: false
+    description: |
+      URL to post into the GitHub commit status when Google Internal
+      tests need to be run. This is useful for helping other Googlers.
+runs:
+  using: 'node16'
+  main: 'main.js'

github-actions/google-internal-tests/lib/BUILD.bazel

@@ -0,0 +1,15 @@
+load("//tools:defaults.bzl", "ts_library")
+
+package(default_visibility = ["//github-actions/google-internal-tests:__subpackages__"])
+
+ts_library(
+    name = "lib",
+    srcs = glob(["*.ts"]),
+    deps = [
+        "@npm//@actions/core",
+        "@npm//@actions/github",
+        "@npm//@octokit/rest",
+        "@npm//@types/minimatch",
+        "@npm//minimatch",
+    ],
+)

github-actions/google-internal-tests/lib/main.ts

@@ -0,0 +1,79 @@
+import core from '@actions/core';
+import {context} from '@actions/github';
+import {Octokit} from '@octokit/rest';
+import minimatch from 'minimatch';
+
+async function main() {
+  if (context.repo.owner !== 'angular') {
+    core.info('Skipping Google Internal Tests action for non-Angular repos.');
+    return;
+  }
+  if (context.eventName !== 'pull_request_target' || context.payload.action !== 'synchronize') {
+    throw new Error(
+      'Expected Google Internal Tests action to be triggered for ' +
+        '`pull_request_target.synchronize` events.',
+    );
+  }
+
+  const githubToken = core.getInput('github-token', {required: true});
+  const rawPatterns = core.getInput('affected-file-patterns', {required: true});
+  const runTestGuideURL = core.getInput('run-tests-guide-url', {required: false});
+  const patterns = constructPatterns(rawPatterns);
+
+  const github = new Octokit({auth: githubToken});
+  const prNum = context.payload.pull_request!.number;
+  const prHeadSHA = context.payload.pull_request!.head!.sha;
+
+  const files = await github.paginate(github.pulls.listFiles, {
+    ...context.repo,
+    pull_number: prNum,
+  });
+
+  let affectsGoogle = false;
+  for (const f of files) {
+    if (patterns.some((p) => p.match(f.filename))) {
+      affectsGoogle = true;
+      break;
+    }
+  }
+
+  const status = affectsGoogle
+    ? ({
+        state: 'pending',
+        // The initial waiting status is expected to be overridden by the
+        // internal presubmit status service then.
+        description: `Waiting for Google Internal Tests. ${
+          runTestGuideURL ? `@Googlers: See Details for instructions -->` : ''
+        }`.trim(),
+        url: runTestGuideURL,
+      } as const)
+    : ({
+        state: 'success',
+        description: 'Does not affect Google.',
+      } as const);
+
+  await github.repos.createCommitStatus({
+    ...context.repo,
+    sha: prHeadSHA,
+    state: status.state,
+    description: status.description,
+    context: 'google-internal-tests',
+    target_url: status.url,
+  });
+}
+
+function constructPatterns(rawPatterns: string): minimatch.IMinimatch[] {
+  const patterns: minimatch.IMinimatch[] = [];
+  for (let p of rawPatterns.split(/\r?\n/g)) {
+    p = p.trim();
+    if (p !== '') {
+      patterns.push(new minimatch.Minimatch(p));
+    }
+  }
+  return patterns;
+}
+
+main().catch((e: Error) => {
+  core.error(e);
+  core.setFailed(e.message);
+});