test(@angular-devkit/build-angular): port several unit tests to esbuild builder

The following unit tests have been ported over to test the experimental esbuild-based
browser application builder:

* `assets` option
* `outputHashing` option
* browser support behavior (`browserslist`)

Several small modifications were necessary to accommodate output file differences such
as no runtime chunk. Additionally, two tests are temporarily disabled for the `outputHashing`
tests pending implementation in the builder. These tests are the same stylesheet resource handling
file name test and no hashing of non-injected styles test.

Author: clydin

packages/angular_devkit/build_angular/src/builders/browser-esbuild/tests/behavior/browser-support_spec.ts

@@ -0,0 +1,116 @@
+/**
+ * @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.io/license
+ */
+
+import { buildEsbuildBrowser } from '../../index';
+import { BASE_OPTIONS, BROWSER_BUILDER_INFO, describeBuilder } from '../setup';
+
+describeBuilder(buildEsbuildBrowser, BROWSER_BUILDER_INFO, (harness) => {
+  describe('Behavior: "Browser support"', () => {
+    it('creates correct sourcemaps when downleveling async functions', async () => {
+      // Add a JavaScript file with async code
+      await harness.writeFile(
+        'src/async-test.js',
+        'async function testJs() { console.log("from-async-js-function"); }',
+      );
+
+      // Add an async function to the project as well as JavaScript file
+      // The type `Void123` is used as a unique identifier for the final sourcemap
+      // If sourcemaps are not properly propagated then it will not be in the final sourcemap
+      await harness.modifyFile(
+        'src/main.ts',
+        (content) =>
+          'import "./async-test";\n' +
+          content +
+          '\ntype Void123 = void;' +
+          `\nasync function testApp(): Promise<Void123> { console.log("from-async-app-function"); }`,
+      );
+
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+        sourceMap: {
+          scripts: true,
+        },
+      });
+
+      const { result } = await harness.executeOnce();
+
+      expect(result?.success).toBe(true);
+      harness.expectFile('dist/main.js').content.not.toMatch(/\sasync\s+function\s/);
+      harness.expectFile('dist/main.js.map').content.toContain('Promise<Void123>');
+    });
+
+    it('downlevels async functions ', async () => {
+      // Add an async function to the project
+      await harness.writeFile(
+        'src/main.ts',
+        'async function test(): Promise<void> { console.log("from-async-function"); }\ntest();',
+      );
+
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+      });
+
+      const { result } = await harness.executeOnce();
+
+      expect(result?.success).toBe(true);
+      harness.expectFile('dist/main.js').content.not.toMatch(/\sasync\s/);
+      harness.expectFile('dist/main.js').content.toContain('"from-async-function"');
+    });
+
+    it('warns when IE is present in browserslist', async () => {
+      await harness.appendToFile(
+        '.browserslistrc',
+        `
+           IE 9
+           IE 11
+         `,
+      );
+
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+      });
+
+      const { result, logs } = await harness.executeOnce();
+      expect(result?.success).toBeTrue();
+
+      expect(logs).toContain(
+        jasmine.objectContaining({
+          level: 'warn',
+          message:
+            `One or more browsers which are configured in the project's Browserslist ` +
+            'configuration will be ignored as ES5 output is not supported by the Angular CLI.\n' +
+            'Ignored browsers: ie 11, ie 9',
+        }),
+      );
+    });
+
+    it('downlevels "for await...of"', async () => {
+      // Add an async function to the project
+      await harness.writeFile(
+        'src/main.ts',
+        `
+          (async () => {
+            for await (const o of [1, 2, 3]) {
+              console.log("for await...of");
+            }
+          })();
+          `,
+      );
+
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+      });
+
+      const { result } = await harness.executeOnce();
+
+      expect(result?.success).toBe(true);
+      harness.expectFile('dist/main.js').content.not.toMatch(/\sawait\s/);
+      harness.expectFile('dist/main.js').content.toContain('"for await...of"');
+    });
+  });
+});