build: fix failing nightly snapshot tests (#14395)

* build: fix failing nightly snapshot tests

* Fix comment typos

.circleci/config.yml

@@ -279,7 +279,7 @@ jobs:
     - *restore_cache
     - *yarn_install
 
-    - run: ./scripts/install-angular-snapshots.sh
+    - run: node ./scripts/circleci/setup-angular-snapshots.js
     - run: ./scripts/circleci/run-local-browser-tests.sh
 
 # ----------------------------------------------------------------------------------------

scripts/circleci/setup-angular-snapshots.js

@@ -0,0 +1,60 @@
+/**
+ * Script that sets up the Angular snapshot github builds. We set up the snapshot builds by
+ * overwriting the versions in the "package.json" and taking advantage of Yarn's resolutions
+ * feature. Yarn resolutions will be used to flatten nested Angular packages because by default
+ * Yarn does not flatten any dependency. See:
+ *
+ *  node_modules/compiler@snapshot
+ *  node_modules/compiler-cli@snapshot
+ *    node_modules/compiler@7.0.1
+ *
+ * Note that we cannot just use Yarn's `--flat` option because that would mean that it tries
+ * to flatten **all** dependencies and could cause unexpected results. We **only** want to
+ * explicitly flatten out all `@angular/*` dependencies. This can be achieved with resolutions.
+ * Read more here: https://yarnpkg.com/lang/en/docs/package-json/#toc-resolutions
+ */
+
+const {yellow, green} = require('chalk');
+const {writeFileSync} = require('fs');
+const {join} = require('path');
+const {execSync} = require('child_process');
+
+const projectDir = join(__dirname, '../../');
+const packageJsonPath = join(projectDir, 'package.json');
+const packageJson = require(packageJsonPath);
+
+// Initialize the "resolutions" property in case it is not present in the "package.json" yet.
+// See: https://yarnpkg.com/lang/en/docs/package-json/#toc-resolutions for the API.
+packageJson['resolutions'] = packageJson['resolutions'] || {};
+
+// List that contains the names of all installed Angular packages (e.g. "@angular/core")
+const angularPackages = Object.keys({...packageJson.dependencies, ...packageJson.devDependencies})
+  .filter(packageName => packageName.startsWith('@angular/'));
+
+console.log(green('Setting up snapshot builds for:\n'));
+console.log(yellow(`  ${angularPackages.join('\n  ')}\n`));
+
+// Setup the snapshot version for each Angular package specified in the "package.json" file.
+angularPackages.forEach(packageName => {
+  const buildsUrl = `github:angular/${packageName.split('/')[1]}-builds`;
+  // Add resolutions for each package in the format "**/{PACKAGE}" so that all
+  // nested versions of that specific Angular package will have the same version.
+  packageJson.resolutions[`**/${packageName}`] = buildsUrl;
+
+  // Since the resolutions only cover the version of all nested installs, we also need
+  // to explicitly set the version for the package listed in the project "package.json".
+  packageJson.dependencies[packageName] = buildsUrl;
+
+  // In case this dependency was previously a dev dependency, just remove it because we
+  // re-added it as a normal dependency for simplicity.
+  delete packageJson.devDependencies[packageName];
+});
+
+// Write changes to the "packageJson", so that we can install the new versions afterwards.
+writeFileSync(packageJsonPath, JSON.stringify(packageJson, null, 2));
+
+console.log(green('Successfully added the "resolutions" to the "package.json".'));
+
+// Run "yarn" in the directory that contains the "package.json". Also pipe all output to the
+// current process so that everything can be debugged within CircleCI.
+execSync('yarn', {cwd: projectDir, stdio: 'inherit', shell: true});