feat(@angular-devkit/build-angular): remove differential loading support

BREAKING CHANGE:
Differential loading support has been removed. With Angular no longer supporting IE11, there are now no browsers officially supported by Angular that require ES5 code. As a result, differential loading's functionality for creating and conditionally loading ES5 and ES2015+ variants of an application is no longer required.

packages/angular_devkit/build_angular/src/browser/specs/browser-support_spec.ts

@@ -17,9 +17,6 @@ describe('Browser Builder browser support', () => {
   beforeEach(async () => {
     await host.initialize().toPromise();
     architect = (await createArchitect(host.root())).architect;
-
-    // target ES5 to disable differential loading which is not needed for the tests
-    host.replaceInFile('tsconfig.json', '"target": "es2017"', '"target": "es5"');
   });
   afterEach(async () => host.restore().toPromise());
 

packages/angular_devkit/build_angular/src/browser/specs/scripts-array_spec.ts

@@ -75,40 +75,6 @@ describe('Browser Builder scripts array', () => {
     }
   });
 
-  it('works in watch mode with differential loading', async () => {
-    const matches: Record<string, string> = {
-      'scripts.js': 'input-script',
-      'lazy-script.js': 'lazy-script',
-      'renamed-script.js': 'pre-rename-script',
-      'renamed-lazy-script.js': 'pre-rename-lazy-script',
-      'main-es2017.js': 'input-script',
-      'index.html':
-        '<script src="runtime-es2017.js" type="module"></script>' +
-        '<script src="polyfills-es2017.js" type="module"></script>' +
-        '<script src="scripts.js" defer></script>' +
-        '<script src="renamed-script.js" defer></script>' +
-        '<script src="vendor-es2017.js" type="module"></script>' +
-        '<script src="main-es2017.js" type="module"></script>',
-    };
-
-    host.writeMultipleFiles(scripts);
-    host.appendToFile('src/main.ts', "\nimport './input-script.js';");
-
-    // Enable differential loading
-    host.appendToFile('.browserslistrc', '\nIE 11');
-
-    // Remove styles so we don't have to account for them in the index.html order check.
-    const { files } = await browserBuild(architect, host, target, {
-      styles: [],
-      scripts: getScriptsOption(),
-      watch: true,
-    } as {});
-
-    for (const [fileName, content] of Object.entries(matches)) {
-      expect(await files[fileName]).toMatch(content);
-    }
-  });
-
   it('uglifies, uses sourcemaps, and adds hashes', async () => {
     host.writeMultipleFiles(scripts);
 

packages/angular_devkit/build_angular/src/browser/specs/styles_spec.ts

@@ -140,9 +140,6 @@ describe('Browser Builder styles', () => {
       '.browserslistrc': 'IE 10',
     });
 
-    // Set target to ES5 to avoid differential loading and unnecessary testing time
-    host.replaceInFile('tsconfig.json', '"target": "es2017"', '"target": "es5"');
-
     const { files } = await browserBuild(architect, host, target, { aot: false });
 
     expect(await files['main.js']).toContain('-ms-flex: 1;');
@@ -165,9 +162,6 @@ describe('Browser Builder styles', () => {
       '.browserslistrc': 'IE 10',
     });
 
-    // Set target to ES5 to avoid differential loading and unnecessary testing time
-    host.replaceInFile('tsconfig.json', '"target": "es2017"', '"target": "es5"');
-
     const { files } = await browserBuild(architect, host, target, { aot: true });
 
     expect(await files['main.js']).toContain('-ms-flex: 1;');
@@ -354,9 +348,6 @@ describe('Browser Builder styles', () => {
       '.browserslistrc': 'IE 10',
     });
 
-    // Set to target to ES5 to avoid differential loading and unnecessary testing time
-    host.replaceInFile('tsconfig.json', '"target": "es2017"', '"target": "es5"');
-
     const overrides = { extractCss: true, optimization: false };
     const { files } = await browserBuild(architect, host, target, overrides);
     expect(await files['styles.css']).toContain(tags.stripIndents`
@@ -394,9 +385,6 @@ describe('Browser Builder styles', () => {
       '.browserslistrc': 'IE 10',
     });
 
-    // Set target to ES5 to avoid differential loading and unnecessary testing time
-    host.replaceInFile('tsconfig.json', '"target": "es2017"', '"target": "es5"');
-
     const overrides = { extractCss: true, optimization: true, styles: ['src/styles.scss'] };
     const { files } = await browserBuild(architect, host, target, overrides);
     expect(await files['styles.css']).toContain('-ms-grid-columns:100px;');

packages/angular_devkit/build_angular/src/dev-server/index.ts

@@ -16,13 +16,12 @@ import { json, tags } from '@angular-devkit/core';
 import * as path from 'path';
 import { Observable, from } from 'rxjs';
 import { concatMap, switchMap } from 'rxjs/operators';
-import * as ts from 'typescript';
 import * as url from 'url';
 import webpack from 'webpack';
 import webpackDevServer from 'webpack-dev-server';
 import { Schema as BrowserBuilderSchema, OutputHashing } from '../browser/schema';
 import { ExecutionTransformer } from '../transforms';
-import { BuildBrowserFeatures, normalizeOptimization } from '../utils';
+import { normalizeOptimization } from '../utils';
 import { findCachePath } from '../utils/cache-path';
 import { checkPort } from '../utils/check-port';
 import { colors } from '../utils/color';
@@ -303,17 +302,10 @@ export function serveWebpackBrowser(
   }
 
   return from(setup()).pipe(
-    switchMap(({ browserOptions, webpackConfig, projectRoot, locale }) => {
+    switchMap(({ browserOptions, webpackConfig, locale }) => {
       if (browserOptions.index) {
-        const { scripts = [], styles = [], baseHref, tsConfig } = browserOptions;
-        const { options: compilerOptions } = readTsconfig(tsConfig, workspaceRoot);
-        const target = compilerOptions.target || ts.ScriptTarget.ES5;
-        const buildBrowserFeatures = new BuildBrowserFeatures(projectRoot);
-
+        const { scripts = [], styles = [], baseHref } = browserOptions;
         const entrypoints = generateEntryPoints({ scripts, styles });
-        const moduleEntrypoints = buildBrowserFeatures.isDifferentialLoadingNeeded(target)
-          ? generateEntryPoints({ scripts: [], styles })
-          : [];
 
         webpackConfig.plugins = [...(webpackConfig.plugins || [])];
         webpackConfig.plugins.push(
@@ -322,7 +314,7 @@ export function serveWebpackBrowser(
             outputPath: getIndexOutputFile(browserOptions.index),
             baseHref,
             entrypoints,
-            moduleEntrypoints,
+            moduleEntrypoints: [],
             noModuleEntrypoints: ['polyfills-es5'],
             deployUrl: browserOptions.deployUrl,
             sri: browserOptions.subresourceIntegrity,