fix(@angular-devkit/build-angular): show error for missing modules

packages/angular_devkit/build_angular/src/angular-cli-files/models/webpack-configs/common.ts

@@ -353,6 +353,8 @@ export function getCommonConfig(wco: WebpackConfigOptions): Configuration {
       hints: false,
     },
     module: {
+      // Show an error for missing exports instead of a warning.
+      strictExportPresence: true,
       rules: [
         {
           test: /\.(eot|svg|cur|jpg|png|webp|gif|otf|ttf|woff|woff2|ani)$/,

packages/angular_devkit/build_angular/test/browser/errors_spec_large.ts

@@ -62,4 +62,23 @@ describe('Browser Builder errors', () => {
     expect(logs.join()).toContain('Function expressions are not supported in');
     await run.stop();
   });
+
+  it('shows missing export errors', async () => {
+    host.writeMultipleFiles({
+      'src/not-main.js': `
+        import { missingExport } from 'rxjs';
+        console.log(missingExport);
+      `,
+    });
+    const overrides = { main: 'src/not-main.js' };
+    const logger = new logging.Logger('');
+    const logs: string[] = [];
+    logger.subscribe(e => logs.push(e.message));
+
+    const run = await architect.scheduleTarget(targetSpec, overrides, { logger });
+    const output = await run.result;
+    expect(output.success).toBe(false);
+    expect(logs.join()).toContain(`export 'missingExport' was not found in 'rxjs'`);
+    await run.stop();
+  });
 });