fix(language-service): do not throw for invalid metadata (#13261)

Fixes #13255

modules/@angular/language-service/test/template_references_spec.ts

@@ -9,7 +9,7 @@
 import * as ts from 'typescript';
 
 import {createLanguageService} from '../src/language_service';
-import {Completions, Diagnostic, Diagnostics} from '../src/types';
+import {Completions, Diagnostic, Diagnostics, LanguageService} from '../src/types';
 import {TypeScriptServiceHost} from '../src/typescript_host';
 
 import {toh} from './test_data';
@@ -17,16 +17,42 @@ import {MockTypescriptHost} from './test_utils';
 
 describe('references', () => {
   let documentRegistry = ts.createDocumentRegistry();
-  let mockHost = new MockTypescriptHost(['/app/main.ts', '/app/parsing-cases.ts'], toh);
-  let service = ts.createLanguageService(mockHost, documentRegistry);
-  let program = service.getProgram();
-  let ngHost = new TypeScriptServiceHost(mockHost, service);
-  let ngService = createLanguageService(ngHost);
-  ngHost.setSite(ngService);
+  let mockHost: MockTypescriptHost;
+  let service: ts.LanguageService;
+  let program: ts.Program;
+  let ngHost: TypeScriptServiceHost;
+  let ngService: LanguageService = createLanguageService(ngHost);
+
+  beforeEach(() => {
+    mockHost = new MockTypescriptHost(['/app/main.ts', '/app/parsing-cases.ts'], toh);
+    service = ts.createLanguageService(mockHost, documentRegistry);
+    program = service.getProgram();
+    ngHost = new TypeScriptServiceHost(mockHost, service);
+    ngService = createLanguageService(ngHost);
+    ngHost.setSite(ngService);
+  });
 
   it('should be able to get template references',
      () => { expect(() => ngService.getTemplateReferences()).not.toThrow(); });
 
   it('should be able to determine that test.ng is a template reference',
      () => { expect(ngService.getTemplateReferences()).toContain('/app/test.ng'); });
+
+  it('should be able to get template references for an invalid project', () => {
+    const moduleCode = `
+      import {NgModule} from '@angular/core';
+      import {NewClass} from './test.component';
+
+      @NgModule({declarations: [NewClass]}) export class TestModule {}`;
+    const classCode = `
+      export class NewClass {}
+
+      @Component({})
+      export class SomeComponent {}
+    `;
+    mockHost.addScript('/app/test.module.ts', moduleCode);
+    mockHost.addScript('/app/test.component.ts', classCode);
+    expect(() => { ngService.getTemplateReferences(); }).not.toThrow();
+  });
+
 });