feat(language-service): Show documentation on hover (#34506)

This commit adds dpcumentation to the hover tooltip.

PR closes https://github.com/angular/vscode-ng-language-service/issues/321

PR Close #34506

packages/language-service/test/hover_spec.ts

@@ -205,6 +205,24 @@ describe('hover', () => {
     });
     expect(toText(displayParts)).toBe('(method) $any: $any');
   });
+
+  it('should provide documentation for a property', () => {
+    mockHost.override(TEST_TEMPLATE, `<div>{{~{cursor}title}}</div>`);
+    const marker = mockHost.getLocationMarkerFor(TEST_TEMPLATE, 'cursor');
+    const quickInfo = ngLS.getHoverAt(TEST_TEMPLATE, marker.start);
+    expect(quickInfo).toBeDefined();
+    const documentation = toText(quickInfo !.documentation);
+    expect(documentation).toBe('This is the title of the `TemplateReference` Component.');
+  });
+
+  it('should provide documentation for a selector', () => {
+    mockHost.override(TEST_TEMPLATE, `<~{cursor}test-comp></test-comp>`);
+    const marker = mockHost.getLocationMarkerFor(TEST_TEMPLATE, 'cursor');
+    const quickInfo = ngLS.getHoverAt(TEST_TEMPLATE, marker.start);
+    expect(quickInfo).toBeDefined();
+    const documentation = toText(quickInfo !.documentation);
+    expect(documentation).toBe('This Component provides the `test-comp` selector.');
+  });
 });
 
 function toText(displayParts?: ts.SymbolDisplayPart[]): string {

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

@@ -132,6 +132,9 @@ export class AsyncForUsingComponent {
 export class References {
 }
 
+/**
+ * This Component provides the `test-comp` selector.
+ */
 /*BeginTestComponent*/ @Component({
   selector: 'test-comp',
   template: '<div>Testing: {{name}}</div>',
@@ -145,6 +148,9 @@ export class TestComponent {
   templateUrl: 'test.ng',
 })
 export class TemplateReference {
+  /**
+   * This is the title of the `TemplateReference` Component.
+   */
   title = 'Some title';
   hero: Hero = {id: 1, name: 'Windstorm'};
   heroes: Hero[] = [this.hero];