fix(core): include signal and component name in NG0600 error message

The signals primitives already pass the written signal node to the
error handler, but core ignored it. In dev mode the message now names
the signal (when it has a debugName) and the component whose template
was rendering. Production output is unchanged.

Author: arturovt

packages/core/src/application/application_ref.ts

@@ -38,6 +38,7 @@ import {ComponentFactory} from '../render3/component_ref';
 import {getComponentDef, isStandalone} from '../render3/def_getters';
 import type {Binding, DirectiveWithBindings} from '../render3/dynamic_bindings';
 import {ChangeDetectionMode, detectChangesInternal} from '../render3/instructions/change_detection';
+import {getDeclarationComponentDef} from '../render3/instructions/element_validation';
 import {profiler} from '../render3/profiler';
 import {isReactiveLViewConsumer} from '../render3/reactive_lview_consumer';
 import {EffectScheduler} from '../render3/reactivity/root_effect_scheduler';
@@ -71,14 +72,24 @@ export function publishDefaultGlobalUtils() {
  * Sets the error for an invalid write to a signal to be an Angular `RuntimeError`.
  */
 export function publishSignalConfiguration(): void {
-  setThrowInvalidWriteToSignalError(() => {
+  setThrowInvalidWriteToSignalError((node) => {
     let errorMessage = '';
     if (ngDevMode) {
       const activeConsumer = getActiveConsumer();
-      errorMessage =
-        activeConsumer && isReactiveLViewConsumer(activeConsumer)
-          ? 'Writing to signals is not allowed while Angular renders the template (eg. interpolations)'
-          : 'Writing to signals is not allowed in a `computed`';
+      if (activeConsumer && isReactiveLViewConsumer(activeConsumer)) {
+        errorMessage =
+          'Writing to signals is not allowed while Angular renders the template (eg. interpolations)';
+        const componentName =
+          activeConsumer.lView && getDeclarationComponentDef(activeConsumer.lView)?.type?.name;
+        if (componentName) {
+          errorMessage += `. Template location: '${componentName}' component`;
+        }
+      } else {
+        errorMessage = 'Writing to signals is not allowed in a `computed`';
+      }
+      if (node.debugName) {
+        errorMessage += `. Signal: '${node.debugName}'`;
+      }
     }
     throw new RuntimeError(RuntimeErrorCode.SIGNAL_WRITE_FROM_ILLEGAL_CONTEXT, errorMessage);
   });

packages/core/test/render3/reactivity_spec.ts

@@ -865,6 +865,59 @@ describe('reactivity', () => {
       expect(() => fixture.detectChanges()).toThrowError(/NG0600.*template/);
     });
 
+    it('should name the component and the signal when writing within a template', async () => {
+      @Component({
+        selector: 'write-in-template',
+        template: '@if (true) {{{write()}}}',
+      })
+      class WriteInTemplate {
+        sig = signal(0, {debugName: 'count'});
+        write() {
+          this.sig.set(1);
+        }
+      }
+
+      const fixture = TestBed.createComponent(WriteInTemplate);
+
+      await expectAsync(fixture.whenStable()).toBeRejectedWithError(
+        /^NG0600: Writing to signals is not allowed while Angular renders the template \(eg\. interpolations\)\. Template location: 'WriteInTemplate' component\. Signal: 'count'\. Find more at/,
+      );
+    });
+
+    it('should name the signal when writing within computed', async () => {
+      @Component({
+        selector: 'write-in-computed',
+        template: '{{comp()}}',
+      })
+      class WriteInComputed {
+        sig = signal(0, {debugName: 'count'});
+        comp = computed(() => this.sig.set(1));
+      }
+
+      const fixture = TestBed.createComponent(WriteInComputed);
+
+      await expectAsync(fixture.whenStable()).toBeRejectedWithError(
+        /^NG0600: Writing to signals is not allowed in a `computed`\. Signal: 'count'\. Find more at/,
+      );
+    });
+
+    it('should keep the message short when the signal has no debugName', async () => {
+      @Component({
+        selector: 'write-in-computed',
+        template: '{{comp()}}',
+      })
+      class WriteInComputed {
+        sig = signal(0);
+        comp = computed(() => this.sig.set(1));
+      }
+
+      const fixture = TestBed.createComponent(WriteInComputed);
+
+      await expectAsync(fixture.whenStable()).toBeRejectedWithError(
+        /^NG0600: Writing to signals is not allowed in a `computed`\. Find more at/,
+      );
+    });
+
     describe('effects created in components should first run after ngOnInit', () => {
       it('when created during bootstrapping', () => {
         let log: string[] = [];