Handle errors in Predicate function

source/event-emitter.ts

@@ -181,7 +181,12 @@ export class EventEmitter<T extends EventMap> {
 
             // Create a listener function.
             const listener = (payload: Readonly<T[K]>): void => {
-                if (predicate(payload)) {
+                try {
+                    // If the event payload does not match the predicate condition, return.
+                    if (!predicate(payload)) {
+                        return;
+                    }
+
                     // Clean up
                     this.off(type, listener);
                     if (timeoutId !== undefined) {
@@ -189,6 +194,8 @@ export class EventEmitter<T extends EventMap> {
                     }
 
                     resolve(payload);
+                } catch (error) {
+                    reject(error);
                 }
             };
 

test/event-emitter.test.ts

@@ -491,6 +491,23 @@ const testEventEmitterDebouncedOnceListener = async (): Promise<void> => {
     }
 };
 
+/**
+ * Tests that the `waitFor` method rejects if the predicate function throws
+ */
+const testEventEmitterWaitForRejectsOnPredicateError = async (): Promise<void> => {
+    const emitter = new EventEmitter<TestEvents>();
+    const listener = vi.fn();
+
+    const waitPromise = emitter.waitFor('message', () => {
+        throw new Error('predicate error');
+    });
+
+    emitter.emit('message', 'hello');
+
+    await expect(waitPromise).rejects.toThrow('predicate error');
+    expect(listener).not.toHaveBeenCalled();
+};
+
 const runTests = async (): Promise<void> => {
     test('EventEmitter: calls listeners when an event is emitted', testEventEmitterCallsListeners);
     test('EventEmitter: calls multiple listeners for the same event', testEventEmitterCallsMultipleListeners);
@@ -516,6 +533,7 @@ const runTests = async (): Promise<void> => {
     test('EventEmitter: resets the debounce timer on repeated emits', testEventEmitterDebouncedTimerResetsOnRepeatedEmits);
     test('EventEmitter: does not debounce when debounceMilliseconds is zero', testEventEmitterZeroDebounceDoesNotDebounce);
     test('EventEmitter: debounces once listeners and invokes them only once', testEventEmitterDebouncedOnceListener);
+    test('EventEmitter: rejects waitFor when the predicate function throws', testEventEmitterWaitForRejectsOnPredicateError);
 };
 
 await runTests();