fix(language-service): Diagnostic span should point to class name (#34932)

Right now, if an Angular diagnostic is generated for a TypeScript node,
the span points to the decorator Identifier, i.e. the Identifier node
like `@NgModule`, `@Component`, etc.
This is weird. It should point to the class name instead.
Note, we do not have a more fine-grained breakdown of the span when
diagnostics are emitted, this work remains to be done.

PR Close #34932

packages/language-service/src/typescript_host.ts

@@ -288,9 +288,9 @@ export class TypeScriptServiceHost implements LanguageServiceHost {
     const visit = (child: tss.Node) => {
       const candidate = getDirectiveClassLike(child);
       if (candidate) {
-        const {decoratorId, classDecl} = candidate;
-        const declarationSpan = spanOf(decoratorId);
-        const className = classDecl.name !.text;
+        const {classId} = candidate;
+        const declarationSpan = spanOf(classId);
+        const className = classId.getText();
         const classSymbol = this.reflector.getStaticSymbol(sourceFile.fileName, className);
         // Ask the resolver to check if candidate is actually Angular directive
         if (!this.resolver.isDirective(classSymbol)) {

packages/language-service/src/utils.ts

@@ -164,8 +164,8 @@ export function findTightestNode(node: ts.Node, position: number): ts.Node|undef
 }
 
 interface DirectiveClassLike {
-  decoratorId: ts.Identifier;  // decorator identifier
-  classDecl: ts.ClassDeclaration;
+  decoratorId: ts.Identifier;  // decorator identifier, like @Component
+  classId: ts.Identifier;
 }
 
 /**
@@ -178,11 +178,11 @@ interface DirectiveClassLike {
  *
  * For example,
  *     v---------- `decoratorId`
- * @NgModule({
- *   declarations: [],
- * })
- * class AppModule {}
- *          ^----- `classDecl`
+ * @NgModule({           <
+ *   declarations: [],   < classDecl
+ * })                    <
+ * class AppModule {}    <
+ *          ^----- `classId`
  *
  * @param node Potential node that represents an Angular directive.
  */
@@ -200,7 +200,7 @@ export function getDirectiveClassLike(node: ts.Node): DirectiveClassLike|undefin
     if (ts.isObjectLiteralExpression(arg)) {
       return {
         decoratorId: expr.expression,
-        classDecl: node,
+        classId: node.name,
       };
     }
   }

packages/language-service/test/diagnostics_spec.ts

@@ -354,9 +354,7 @@ describe('diagnostics', () => {
         .toBe(
             `Component 'MyComponent' is not included in a module and will not be available inside a template. Consider adding it to a NgModule declaration.`);
     const content = mockHost.readFile(fileName) !;
-    const keyword = '@Component';
-    expect(start).toBe(content.lastIndexOf(keyword) + 1);  // exclude leading '@'
-    expect(length).toBe(keyword.length - 1);               // exclude leading '@'
+    expect(content.substring(start !, start ! + length !)).toBe('MyComponent');
   });
 
 
@@ -596,9 +594,7 @@ describe('diagnostics', () => {
         .toBe(
             'Invalid providers for "AppComponent in /app/app.component.ts" - only instances of Provider and Type are allowed, got: [?null?]');
     // TODO: Looks like this is the wrong span. Should point to 'null' instead.
-    const keyword = '@Component';
-    expect(start).toBe(content.lastIndexOf(keyword) + 1);  // exclude leading '@'
-    expect(length).toBe(keyword.length - 1);               // exclude leading '@
+    expect(content.substring(start !, start ! + length !)).toBe('AppComponent');
   });
 
   // Issue #15768
@@ -767,8 +763,7 @@ describe('diagnostics', () => {
       const {file, messageText, start, length} = diags[0];
       expect(file !.fileName).toBe(APP_COMPONENT);
       expect(messageText).toBe(`Component 'AppComponent' must have a template or templateUrl`);
-      expect(start).toBe(content.indexOf(`@Component`) + 1);
-      expect(length).toBe('Component'.length);
+      expect(content.substring(start !, start ! + length !)).toBe('AppComponent');
     });
 
     it('should report diagnostic for both template and templateUrl', () => {
@@ -787,8 +782,7 @@ describe('diagnostics', () => {
       expect(file !.fileName).toBe(APP_COMPONENT);
       expect(messageText)
           .toBe(`Component 'AppComponent' must not have both template and templateUrl`);
-      expect(start).toBe(content.indexOf(`@Component`) + 1);
-      expect(length).toBe('Component'.length);
+      expect(content.substring(start !, start ! + length !)).toBe('AppComponent');
     });
 
     it('should report errors for invalid styleUrls', () => {

packages/language-service/test/utils_spec.ts

@@ -28,10 +28,10 @@ describe('getDirectiveClassLike()', () => {
       }
     });
     expect(result).toBeTruthy();
-    const {decoratorId, classDecl} = result !;
+    const {decoratorId, classId} = result !;
     expect(decoratorId.kind).toBe(ts.SyntaxKind.Identifier);
-    expect((decoratorId as ts.Identifier).text).toBe('NgModule');
-    expect(classDecl.name !.text).toBe('AppModule');
+    expect(decoratorId.text).toBe('NgModule');
+    expect(classId.text).toBe('AppModule');
   });
 });