fix(compiler-cli): Produce fatal diagnostic on duplicate decorated properties (#60376)

atscott · thePunderWoman · commit f4c4b10ea8dc · 2025-03-27T20:26:42.000Z
This prevents the compilation and language service from crashing. fixes angular/vscode-ng-language-service#2091 PR Close #60376
diff --git a/goldens/public-api/compiler-cli/error_code.api.md b/goldens/public-api/compiler-cli/error_code.api.md
@@ -43,6 +43,8 @@ export enum ErrorCode {
     DIRECTIVE_INHERITS_UNDECORATED_CTOR = 2006,
     // (undocumented)
     DIRECTIVE_MISSING_SELECTOR = 2004,
+    // (undocumented)
+    DUPLICATE_DECORATED_PROPERTIES = 1012,
     DUPLICATE_VARIABLE_DECLARATION = 8006,
     HOST_BINDING_PARSE_ERROR = 5001,
     HOST_DIRECTIVE_COMPONENT = 2015,
diff --git a/packages/compiler-cli/src/ngtsc/annotations/common/src/metadata.ts b/packages/compiler-cli/src/ngtsc/annotations/common/src/metadata.ts
@@ -6,6 +6,7 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
+import {ErrorCode, FatalDiagnosticError, makeRelatedInformation} from '../../../diagnostics';
 import {
   ArrowFunctionExpr,
   Expression,
@@ -88,16 +89,18 @@ export function extractClassMetadata(
     .filter(
       (member) => !member.isStatic && member.decorators !== null && member.decorators.length > 0,
     );
-  const duplicateDecoratedMemberNames = classMembers
-    .map((member) => member.name)
-    .filter((name, i, arr) => arr.indexOf(name) < i);
-  if (duplicateDecoratedMemberNames.length > 0) {
+  const duplicateDecoratedMembers = classMembers.filter(
+    (member, i, arr) => arr.findIndex((arrayMember) => arrayMember.name === member.name) < i,
+  );
+  if (duplicateDecoratedMembers.length > 0) {
     // This should theoretically never happen, because the only way to have duplicate instance
     // member names is getter/setter pairs and decorators cannot appear in both a getter and the
     // corresponding setter.
-    throw new Error(
+    throw new FatalDiagnosticError(
+      ErrorCode.DUPLICATE_DECORATED_PROPERTIES,
+      duplicateDecoratedMembers[0].nameNode ?? clazz,
       `Duplicate decorated properties found on class '${clazz.name.text}': ` +
-        duplicateDecoratedMemberNames.join(', '),
+        duplicateDecoratedMembers.map((member) => member.name).join(', '),
     );
   }
   const decoratedMembers = classMembers.map((member) =>
diff --git a/packages/compiler-cli/src/ngtsc/diagnostics/src/error_code.ts b/packages/compiler-cli/src/ngtsc/diagnostics/src/error_code.ts
@@ -23,6 +23,8 @@ export enum ErrorCode {
   VALUE_HAS_WRONG_TYPE = 1010,
   VALUE_NOT_LITERAL = 1011,
 
+  DUPLICATE_DECORATED_PROPERTIES = 1012,
+
   /**
    * Raised when an initializer API is annotated with an unexpected decorator.
    *
diff --git a/packages/language-service/test/diagnostic_spec.ts b/packages/language-service/test/diagnostic_spec.ts
@@ -59,6 +59,34 @@ describe('getSemanticDiagnostics', () => {
     expect(messageText).toBe(`Property 'nope' does not exist on type 'AppComponent'.`);
   });
 
+  it('produces diagnostic for duplicate docarated property rather than crashing', () => {
+    const files = {
+      'app.ts': `
+      import {Component, Input} from '@angular/core';
+
+      @Component({
+        template: '',
+      })
+      export class AppComponent {
+        @Input() test1?: string;
+        @Input() test1?: string;
+      }
+    `,
+    };
+    const project = createModuleAndProjectWithDeclarations(env, 'test', files);
+
+    const diags = project.getDiagnosticsForFile('app.ts');
+    expect(diags.length).toBe(2);
+    expect(diags[0].category).toBe(ts.DiagnosticCategory.Error);
+    expect(diags[0].file?.fileName).toBe('/test/app.ts');
+    expect(diags[0].messageText).toBe(`Duplicate identifier 'test1'.`);
+    expect(diags[1].category).toBe(ts.DiagnosticCategory.Error);
+    expect(diags[1].file?.fileName).toBe('/test/app.ts');
+    expect(diags[1].messageText).toBe(
+      `Duplicate decorated properties found on class 'AppComponent': test1`,
+    );
+  });
+
   it('should process external template', () => {
     const files = {
       'app.ts': `

Original file line number	Diff line number	Diff line change
`@@ -23,6 +23,8 @@ export enum ErrorCode {`
`23`	`23`	`VALUE_HAS_WRONG_TYPE = 1010,`
`24`	`24`	`VALUE_NOT_LITERAL = 1011,`
`25`	`25`
	`26`	`+ DUPLICATE_DECORATED_PROPERTIES = 1012,`
	`27`	`+`
`26`	`28`	`/**`
`27`	`29`	`* Raised when an initializer API is annotated with an unexpected decorator.`
`28`	`30`	`*`