feat(language-service): TS references from template items (#37437)

Keen and I were talking about what it would take to support getting
references at a position in the current language service, since it's
unclear when more investment in the Ivy LS will be available. Getting TS
references from a template is trivial -- we simply need to get the
definition of a symbol, which is already handled by the language
service, and ask the TS language service to give us the references for
that definition.

This doesn't handle references in templates, but that could be done in a
subsequent pass.

Part of https://github.com/angular/vscode-ng-language-service/issues/29

PR Close #37437

packages/language-service/src/language_service.ts

@@ -98,4 +98,17 @@ class LanguageServiceImpl implements ng.LanguageService {
     const declarations = this.host.getDeclarations(fileName);
     return getTsHover(position, declarations, analyzedModules);
   }
+
+  getReferencesAtPosition(fileName: string, position: number): tss.ReferenceEntry[]|undefined {
+    const defAndSpan = this.getDefinitionAndBoundSpan(fileName, position);
+    if (!defAndSpan?.definitions) {
+      return;
+    }
+    const {definitions} = defAndSpan;
+    const tsDef = definitions.find(def => def.fileName.endsWith('.ts'));
+    if (!tsDef) {
+      return;
+    }
+    return this.host.tsLS.getReferencesAtPosition(tsDef.fileName, tsDef.textSpan.start);
+  }
 }

packages/language-service/src/types.ts

@@ -254,7 +254,7 @@ export interface Diagnostic {
 export type LanguageService = Pick<
     ts.LanguageService,
     'getCompletionsAtPosition'|'getDefinitionAndBoundSpan'|'getQuickInfoAtPosition'|
-    'getSemanticDiagnostics'>;
+    'getSemanticDiagnostics'|'getReferencesAtPosition'>;
 
 /** Information about an Angular template AST. */
 export interface AstResult {

packages/language-service/src/typescript_host.ts

@@ -72,8 +72,7 @@ export class TypeScriptServiceHost implements LanguageServiceHost {
     ngModules: [],
   };
 
-  constructor(
-      readonly tsLsHost: tss.LanguageServiceHost, private readonly tsLS: tss.LanguageService) {
+  constructor(readonly tsLsHost: tss.LanguageServiceHost, readonly tsLS: tss.LanguageService) {
     this.summaryResolver = new AotSummaryResolver(
         {
           loadSummary(_filePath: string) {

packages/language-service/test/BUILD.bazel

@@ -29,6 +29,7 @@ ts_library(
         "definitions_spec.ts",
         "diagnostics_spec.ts",
         "hover_spec.ts",
+        "references_spec.ts",
     ],
     data = [":project"],
     deps = [

packages/language-service/test/definitions_spec.ts

@@ -71,7 +71,7 @@ describe('definitions', () => {
 
     const fileContent = mockHost.readFile(def.fileName);
     expect(fileContent!.substring(def.textSpan.start, def.textSpan.start + def.textSpan.length))
-        .toEqual(`title = 'Some title';`);
+        .toEqual(`title = 'Tour of Heroes';`);
   });
 
   it('should be able to find a method from a call', () => {

packages/language-service/test/project/app/app.component.ts

@@ -24,4 +24,7 @@ export class AppComponent {
   title = 'Tour of Heroes';
   hero: Hero = {id: 1, name: 'Windstorm'};
   private internal: string = 'internal';
+  setTitle(newTitle: string) {
+    this.title = newTitle;
+  }
 }

packages/language-service/test/project/app/parsing-cases.ts

@@ -102,7 +102,7 @@ export class TemplateReference {
   /**
    * This is the title of the `TemplateReference` Component.
    */
-  title = 'Some title';
+  title = 'Tour of Heroes';
   hero: Hero = {id: 1, name: 'Windstorm'};
   heroP = Promise.resolve(this.hero);
   heroes: Hero[] = [this.hero];
@@ -121,4 +121,7 @@ export class TemplateReference {
   constNames = [{name: 'name'}] as const;
   private myField = 'My Field';
   strOrNumber: string|number = '';
+  setTitle(newTitle: string) {
+    this.title = newTitle;
+  }
 }

packages/language-service/test/references_spec.ts

@@ -0,0 +1,78 @@
+/**
+ * @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 * as ts from 'typescript';
+
+import {createLanguageService} from '../src/language_service';
+import {TypeScriptServiceHost} from '../src/typescript_host';
+
+import {MockTypescriptHost} from './test_utils';
+
+const APP_COMPONENT = '/app/app.component.ts';
+const TEST_TEMPLATE = '/app/test.ng';
+
+describe('references', () => {
+  const mockHost = new MockTypescriptHost(['/app/main.ts']);
+  const tsLS = ts.createLanguageService(mockHost);
+  const ngHost = new TypeScriptServiceHost(mockHost, tsLS);
+  const ngLS = createLanguageService(ngHost);
+
+  beforeEach(() => {
+    mockHost.reset();
+  });
+
+  for (const templateStrategy of ['inline', 'external'] as const) {
+    describe(`template: ${templateStrategy}`, () => {
+      describe('component members', () => {
+        it('should get TS references for a member in template', () => {
+          const fileName = overrideTemplate('{{«title»}}');
+          const marker = mockHost.getReferenceMarkerFor(fileName, 'title');
+          const references = ngLS.getReferencesAtPosition(fileName, marker.start)!;
+
+          expect(references).toBeDefined();
+          expect(references.length).toBe(2);
+
+          for (let i = 0; i < references.length; ++i) {
+            // The first reference is declared as a class member.
+            // The second is in `setTitle`.
+            const ref = references[i];
+            expect(getSource(ref)).toBe('title');
+            if (i == 0) {
+              // The first reference is the member declaration, so it should
+              // have a context span pointing to the whole declaration.
+              expect(getSource(ref, 'contextSpan')).toBe('title = \'Tour of Heroes\';');
+            }
+          }
+        });
+      });
+    });
+
+    // TODO: override parsing-cases#TemplateReference for inline templates.
+    const overrideTemplate = (template: string): string => {
+      if (templateStrategy === 'inline') {
+        mockHost.overrideInlineTemplate(APP_COMPONENT, template);
+        return APP_COMPONENT;
+      } else {
+        mockHost.override(TEST_TEMPLATE, template);
+        return TEST_TEMPLATE;
+      }
+    };
+  }
+
+  /**
+   * Gets the source code of a reference entry. By default the reference
+   * `textSpan` is checked, but this can be overridden by specifying `spanKind`.
+   */
+  function getSource(
+      reference: ts.ReferenceEntry, spanKind: 'textSpan'|'contextSpan' = 'textSpan'): string {
+    const span = reference[spanKind]!;
+    const fileName = reference.fileName;
+    const content = mockHost.readFile(fileName)!;
+    return content.substring(span.start, span.start + span.length);
+  }
+});