refactor(core): expose isWritableSignal to the publicApi

This is alongside the already exisiting isSignal()

fixes #64763

Author: JeanMeche

goldens/public-api/core/index.api.md

@@ -1045,6 +1045,9 @@ export function isSignal(value: unknown): value is Signal<unknown>;
 // @public
 export function isStandalone(type: Type<unknown>): boolean;
 
+// @public
+export function isWritableSignal(value: unknown): value is WritableSignal<unknown>;
+
 // @public
 export interface IterableChangeRecord<V> {
     readonly currentIndex: number | null;

packages/core/src/core_reactivity_export_internal.ts

@@ -8,7 +8,7 @@
 
 export {SIGNAL as ɵSIGNAL} from '../primitives/signals';
 
-export {isSignal, Signal, ValueEqualityFn} from './render3/reactivity/api';
+export {isSignal, isWritableSignal, Signal, ValueEqualityFn} from './render3/reactivity/api';
 export {computed, CreateComputedOptions} from './render3/reactivity/computed';
 export {
   CreateSignalOptions,

packages/core/src/render3/instructions/two_way.ts

@@ -10,7 +10,8 @@ import type {EventCallback} from '../../event_delegation_utils';
 import {bindingUpdated} from '../bindings';
 import {SanitizerFn} from '../interfaces/sanitization';
 import {RENDERER} from '../interfaces/view';
-import {isWritableSignal, WritableSignal} from '../reactivity/signal';
+import {isWritableSignal} from '../reactivity/api';
+import {WritableSignal} from '../reactivity/signal';
 import {getCurrentTNode, getLView, getSelectedTNode, getTView, nextBindingIndex} from '../state';
 
 import {listenerInternal} from './listener';

packages/core/src/render3/reactivity/api.ts

@@ -7,6 +7,7 @@
  */
 
 import {SIGNAL} from '../../../primitives/signals';
+import type {WritableSignal} from './signal';
 
 /**
  * A reactive value which notifies consumers of any changes.
@@ -37,3 +38,12 @@ export function isSignal(value: unknown): value is Signal<unknown> {
  * @publicApi 17.0
  */
 export type ValueEqualityFn<T> = (a: T, b: T) => boolean;
+
+/**
+ * Checks if the given `value` is a writeable signal.
+ *
+ * @publicApi 21.1
+ */
+export function isWritableSignal(value: unknown): value is WritableSignal<unknown> {
+  return isSignal(value) && typeof (value as any).set === 'function';
+}

packages/core/src/render3/reactivity/signal.ts

@@ -6,16 +6,9 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import {
-  createSignal,
-  SIGNAL,
-  SignalGetter,
-  SignalNode,
-  signalSetFn,
-  signalUpdateFn,
-} from '../../../primitives/signals';
+import {createSignal, SIGNAL, SignalGetter, SignalNode} from '../../../primitives/signals';
 
-import {isSignal, Signal, ValueEqualityFn} from './api';
+import {Signal, ValueEqualityFn} from './api';
 
 /** Symbol used distinguish `WritableSignal` from other non-writable signals and functions. */
 export const ɵWRITABLE_SIGNAL: unique symbol = /* @__PURE__ */ Symbol('WRITABLE_SIGNAL');
@@ -102,10 +95,3 @@ export function signalAsReadonlyFn<T>(this: SignalGetter<T>): Signal<T> {
   }
   return node.readonlyFn;
 }
-
-/**
- * Checks if the given `value` is a writeable signal.
- */
-export function isWritableSignal(value: unknown): value is WritableSignal<unknown> {
-  return isSignal(value) && typeof (value as any).set === 'function';
-}

packages/core/test/signals/is_signal_spec.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import {computed, isSignal, signal} from '../../src/core';
+import {computed, isSignal, isWritableSignal, signal} from '../../src/core';
 
 describe('isSignal', () => {
   it('should return true for writable signal', () => {
@@ -34,3 +34,30 @@ describe('isSignal', () => {
     expect(isSignal(fn)).toBe(false);
   });
 });
+
+describe('isWritableSignal', () => {
+  it('should return true for writable signal', () => {
+    const writableSignal = signal('Angular');
+    expect(isWritableSignal(writableSignal)).toBe(true);
+  });
+
+  it('should return false for readonly signal', () => {
+    const readonlySignal = computed(() => 10);
+    expect(isWritableSignal(readonlySignal)).toBe(false);
+  });
+
+  it('should return false for primitive', () => {
+    const primitive = 0;
+    expect(isWritableSignal(primitive)).toBe(false);
+  });
+
+  it('should return false for object', () => {
+    const object = {name: 'Angular'};
+    expect(isWritableSignal(object)).toBe(false);
+  });
+
+  it('should return false for function', () => {
+    const fn = () => {};
+    expect(isWritableSignal(fn)).toBe(false);
+  });
+});