fix(@angular-devkit/build-angular): validate extracted i18n messages for duplicates

This change will analyze the extract i18n messages for duplicates and issue warnings for each case.  This provides the same default behavior as the standalone message extractor contained within `@angular/localize`.  Configurability of the behavior of a detected duplicate (ignore, warn, error) will be added in a future feature.

Author: clydin

packages/angular_devkit/build_angular/src/extract-i18n/index.ts

@@ -252,11 +252,37 @@ export async function execute(
     return webpackResult;
   }
 
+  const basePath = config.context || projectRoot;
+
+  const { checkDuplicateMessages } = await import(
+    // tslint:disable-next-line: trailing-comma
+    '@angular/localize/src/tools/src/extract/duplicates'
+  );
+
+  // The filesystem is used to create a relative path for each file
+  // from the basePath.  This relative path is then used in the error message.
+  const checkFileSystem = {
+    relative(from: string, to: string): string {
+      return path.relative(from, to);
+    },
+  };
+  const diagnostics = checkDuplicateMessages(
+    // tslint:disable-next-line: no-any
+    checkFileSystem as any,
+    ivyMessages,
+    'warning',
+    // tslint:disable-next-line: no-any
+    basePath as any,
+  );
+  if (diagnostics.messages.length > 0) {
+    context.logger.warn(diagnostics.formatDiagnostics(''));
+  }
+
   // Serialize all extracted messages
   const serializer = await getSerializer(
     format,
     i18n.sourceLocale,
-    config.context || projectRoot,
+    basePath,
     useLegacyIds,
   );
   const content = serializer.serialize(ivyMessages);

packages/angular_devkit/build_angular/src/extract-i18n/works_spec.ts

@@ -39,6 +39,18 @@ describe('Extract i18n Target', () => {
     }
   }, 30000);
 
+  it('does not emit the application files', async () => {
+    host.appendToFile('src/app/app.component.html', '<p i18n>i18n test</p>');
+
+    const run = await architect.scheduleTarget(extractI18nTargetSpec);
+
+    await expectAsync(run.result).toBeResolvedTo(jasmine.objectContaining({ success: true }));
+
+    await run.stop();
+
+    expect(host.scopedSync().exists(normalize('dist/app/main.js'))).toBeFalse();
+  }, 30000);
+
   it('shows errors', async () => {
     const logger = new logging.Logger('');
     const logs: string[] = [];
@@ -126,4 +138,29 @@ describe('Extract i18n Target', () => {
     expect(virtualFs.fileBufferToString(host.scopedSync().read(extractionFile)))
       .toMatch(/i18n test/);
   }, 30000);
+
+  // DISABLED_FOR_VE
+  (veEnabled ? xit : it)('issues warnings for duplicate message identifiers', async () => {
+    host.appendToFile(
+      'src/app/app.component.ts',
+      'const c = $localize`:@@message-2:message contents`; const d = $localize`:@@message-2:different message contents`;',
+    );
+
+    const logger = new logging.Logger('');
+    const logs: string[] = [];
+    logger.subscribe((e) => logs.push(e.message));
+
+    const run = await architect.scheduleTarget(extractI18nTargetSpec, undefined, { logger });
+    await expectAsync(run.result).toBeResolvedTo(jasmine.objectContaining({ success: true }));
+
+    await run.stop();
+
+    expect(host.scopedSync().exists(extractionFile)).toBe(true);
+
+    const fullLog = logs.join();
+    expect(fullLog).toContain(
+      'Duplicate messages with id',
+    );
+
+  }, 30000);
 });