build: add script to diff local npm package with snapshot repository

This script will be very useful for the `rules_js` migration, as it
allows us to quickly spot differences between the local `npm_package`
target and the valid golden (based on the snapshot repository).

Author: devversion

scripts/diff-release-package.mts

@@ -0,0 +1,124 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.dev/license
+ */
+
+/**
+ * Script that can be used to compare the local `npm_package` snapshot artifact
+ * with the snapshot artifact from GitHub at upstream `HEAD`.
+ *
+ * This is useful during the `rules_js` migration to verify the npm artifact
+ * doesn't differ unexpectedly.
+ *
+ * Run via:
+ *    node --loader ts-node/esm/transpile-only scripts/diff-release-package.mts <pkg-name>
+ */
+
+import { GitClient } from '@angular/ng-dev';
+import childProcess from 'node:child_process';
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+import sh from 'shelljs';
+
+// Do not remove `.git` as we use Git for comparisons later.
+// Also preserve `uniqueId` as it's irrelevant for the diff and not included via Bazel.
+// The `README.md` is also put together outside of Bazel, so ignore it too.
+const SKIP_FILES = ['README.md', 'uniqueId', '.git'];
+
+const packageName = process.argv[2];
+if (!packageName) {
+  console.error('Expected package name to be specified.');
+  process.exit(1);
+}
+
+try {
+  await main(packageName);
+} catch (e) {
+  console.error(e);
+  process.exitCode = 1;
+}
+
+async function main(packageName: string) {
+  const bazel = process.env.BAZEL ?? 'bazel';
+  const git = await GitClient.get();
+  const monorepoData = JSON.parse(fs.readFileSync('./.monorepo.json', 'utf-8'));
+  const targetDir = packageName.replace(/^@/g, '').replace(/-/g, '_');
+
+  const snapshotRepoName = monorepoData.packages[packageName]?.snapshotRepo;
+  const tmpDir = await fs.promises.mkdtemp(
+    path.join(os.tmpdir(), `diff-release-package-${snapshotRepoName.replace(/\//g, '_')}`),
+  );
+
+  console.log(`Cloning snapshot repo (${snapshotRepoName}) into ${tmpDir}..`);
+  git.run(['clone', `https://github.com/${snapshotRepoName}.git`, tmpDir]);
+  console.log(`--> Cloned snapshot repo.`);
+
+  const bazelBinDir = childProcess
+    .spawnSync(bazel, ['info', 'bazel-bin'], {
+      shell: true,
+      encoding: 'utf8',
+    })
+    .stdout.trim();
+  const outputPath = path.join(bazelBinDir, 'packages/', targetDir, 'npm_package');
+
+  // Delete old directory to avoid surprises, or stamping being outdated.
+  await deleteDir(outputPath);
+
+  childProcess.spawnSync(
+    bazel,
+    ['build', `//packages/${targetDir}:npm_package`, '--config=snapshot'],
+    {
+      shell: true,
+      stdio: 'inherit',
+      encoding: 'utf8',
+    },
+  );
+
+  console.log('--> Built npm package with --config=snapshot');
+  console.error(`--> Output: ${outputPath}`);
+
+  const removeTasks: Promise<void>[] = [];
+  for (const subentry of await fs.promises.readdir(tmpDir)) {
+    if (SKIP_FILES.includes(subentry)) {
+      continue;
+    }
+
+    removeTasks.push(
+      fs.promises.rm(path.join(tmpDir, subentry), { recursive: true, maxRetries: 3 }),
+    );
+  }
+  await Promise.all(removeTasks);
+
+  const copyTasks: Promise<void>[] = [];
+  for (const subentry of await fs.promises.readdir(outputPath)) {
+    if (SKIP_FILES.includes(subentry)) {
+      continue;
+    }
+
+    copyTasks.push(
+      fs.promises.cp(path.join(outputPath, subentry), path.join(tmpDir, subentry), {
+        recursive: true,
+      }),
+    );
+  }
+  await Promise.all(copyTasks);
+
+  git.run(['config', 'core.filemode', 'false'], { cwd: tmpDir });
+
+  const diff = git.run(['diff', '--color'], { cwd: tmpDir }).stdout;
+
+  console.log('\n\n----- Diff ------');
+  console.log(diff);
+
+  await deleteDir(tmpDir);
+}
+
+async function deleteDir(dirPath: string) {
+  // Needed as Bazel artifacts are readonly and cannot be deleted otherwise.
+  sh.chmod('-R', 'u+w', dirPath);
+  await fs.promises.rm(dirPath, { recursive: true, force: true, maxRetries: 3 });
+}