build(docs-infra): simplify updating dependencies in docs examples boilerplate (#38992)

Previously, when updating the dependency versions in
`aio/tools/examples/shared/package.json` (which contains all
dependencies used in docs examples projects), one had to manually go
through all boilerplate directories and update the `package.json` files
with the same versions.

This commit simplifies this task by automating it via a Node.js script.

PR Close #38992

aio/tools/examples/UPDATING.md

@@ -9,7 +9,7 @@ Follow these steps to update the examples to the latest versions of Angular (and
 
 - In the [shared/](./shared) folder, run `yarn` to update the dependencies in the [shared/node_modules/](./shared/node_modules) folder and the [shared/yarn.lock](./shared/yarn.lock) file.
 
-- In the [shared/boilerplate/](./shared/boilerplate) folder, go through each sub-folder and update the dependency versions in all `package.json` files to match the ones in [shared/package.json](./shared/package.json).
+- In the [shared/](./shared) folder, run `yarn sync-deps` to update the dependency versions of the `package.json` files in each sub-folder of [shared/boilerplate/](./shared/boilerplate) to match the ones in [shared/package.json](./shared/package.json).
 
 - Follow the steps in the following section to update the rest of the boilerplate files.
 

aio/tools/examples/shared/package.json

@@ -8,7 +8,8 @@
     "protractor": "protractor",
     "webdriver:update": "node ../../../../scripts/webdriver-manager-update.js",
     "preinstall": "node ../../../../tools/yarn/check-yarn.js",
-    "postinstall": "yarn webdriver:update"
+    "postinstall": "yarn webdriver:update",
+    "sync-deps": "node sync-boilerplate-dependencies"
   },
   "//engines-comment": "Keep this in sync with /package.json and /aio/package.json",
   "engines": {

aio/tools/examples/shared/sync-boilerplate-dependencies.js

@@ -0,0 +1,64 @@
+#!/usr/bin/env node
+
+/**
+ * Usage:
+ * ```sh
+ * node sync-boilerplate-dependencies
+ * ```
+ *
+ * Updates the dependency versions of the top-level `package.json` files in each sub-folder of
+ * `./boilerplate/` and `./boilerplate/viewengine/` to match the ones in `./package.json`.
+ */
+const fs = require('fs');
+const path = require('path');
+
+
+const BOILERPLATE_DIR = `${__dirname}/boilerplate`;
+const VIEWENGINE_DIR = `${BOILERPLATE_DIR}/viewengine`;
+const SHARED_PACKAGE_JSON_PATH = `${__dirname}/package.json`;
+
+const sharedPkgJson = loadJsonFile(SHARED_PACKAGE_JSON_PATH);
+const boilerplatePkgJsonPaths = [
+  ...collectPackageJsonFiles(BOILERPLATE_DIR),
+  ...collectPackageJsonFiles(VIEWENGINE_DIR),
+];
+
+boilerplatePkgJsonPaths.forEach(syncDependencies);
+
+// Helpers
+function collectPackageJsonFiles(dirPath) {
+  return fs.readdirSync(dirPath)
+      .map(childName => `${dirPath}/${childName}`)
+      .filter(childPath => fs.statSync(childPath).isDirectory())
+      .map(subDirPath => `${subDirPath}/package.json`)
+      .filter(pkgJsonPath => fs.existsSync(pkgJsonPath));
+}
+
+function loadJsonFile(filePath) {
+  return JSON.parse(fs.readFileSync(filePath, 'utf8'));
+}
+
+function syncDependencies(boilerplatePkgJsonPath) {
+  console.log(`Syncing '${path.relative(__dirname, boilerplatePkgJsonPath)}'...`);
+
+  const boilerplatePkgJson = loadJsonFile(boilerplatePkgJsonPath);
+
+  ['dependencies', 'devDependencies', 'peerDependencies']
+    .filter(depsProp => boilerplatePkgJson.hasOwnProperty(depsProp))
+    .forEach(depsProp => {
+      const srcDeps = sharedPkgJson[depsProp];
+      const dstDeps = boilerplatePkgJson[depsProp];
+
+      for (const dep of Object.keys(dstDeps)) {
+        if (!srcDeps.hasOwnProperty(dep)) {
+          throw new Error(
+              `Unable to update dependency '${dep}' in '${boilerplatePkgJsonPath} > ${depsProp}'. ` +
+              `The dependency is missing from '${SHARED_PACKAGE_JSON_PATH}'.`);
+        }
+
+        dstDeps[dep] = srcDeps[dep];
+      }
+    });
+
+  fs.writeFileSync(boilerplatePkgJsonPath, `${JSON.stringify(boilerplatePkgJson, null, 2)}\n`);
+}