feat: isASignal function allows to check if an object is a signal

force-app/lwc/signals/core.js

@@ -329,4 +329,7 @@ function $resource(fn, source, options) {
     }
   };
 }
-export { $signal, $effect, $computed, $resource };
+function isASignal(anything) {
+  return !!anything && anything.brand === Symbol.for("lwc-signals");
+}
+export { $signal, $effect, $computed, $resource, isASignal };

src/lwc/signals/__tests__/signal-identity.test.ts

@@ -0,0 +1,38 @@
+import { $signal, isASignal } from "../core";
+
+describe("isASignal", () => {
+  test("checks that a value is a signal", () => {
+    const signal = $signal(0);
+    expect(isASignal(signal)).toBe(true);
+  });
+
+  test("checks that a computed is a signal", () => {
+    const signal = $signal(0);
+    const computed = $signal(() => signal.value);
+    expect(isASignal(computed)).toBe(true);
+  });
+
+  test("checks that a value is not a signal", () => {
+    expect(isASignal(0)).toBe(false);
+  });
+
+  test("checks that a function is not a signal", () => {
+    expect(isASignal(() => {})).toBe(false);
+  });
+
+  test("checks that an object is not a signal", () => {
+    expect(isASignal({})).toBe(false);
+  });
+
+  test("checks that an array is not a signal", () => {
+    expect(isASignal([])).toBe(false);
+  });
+
+  test("checks that undefined is not a signal", () => {
+    expect(isASignal(undefined)).toBe(false);
+  });
+
+  test("checks that null is not a signal", () => {
+    expect(isASignal(null)).toBe(false);
+  });
+});

src/lwc/signals/core.ts

@@ -534,4 +534,8 @@ function $resource<ReturnType, Params>(
   };
 }
 
-export { $signal, $effect, $computed, $resource };
+function isASignal(anything: unknown): anything is Signal<unknown> {
+  return !!anything && (anything as Signal<unknown>).brand === Symbol.for("lwc-signals");
+}
+
+export { $signal, $effect, $computed, $resource, isASignal };