Memory leak in MessagingService._delete() method

[shehryar-turing]

Bug Description

The MessagingService._delete() method in the Firebase Messaging SDK has a memory leak issue where resources are not properly cleaned up when the service is deleted.

Root Cause

The current implementation of MessagingService._delete() only returns Promise.resolve() without cleaning up:

1. Timer leak: The logging service starts a recursive setTimeout loop via _processQueue() that continues indefinitely
2. Event listener leak: Event listeners added in factory functions are never removed
3. Missing cleanup: No cleanup of message handlers, log events, or service worker references

Impact

• Memory leaks when Firebase messaging service is deleted
• Timers continue running in the background
• Event listeners remain attached
• Potential performance degradation over time

Affected Code

• packages/messaging/src/messaging-service.ts - _delete() method
• packages/messaging/src/helpers/logToFirelog.ts - _processQueue() timer management
• packages/messaging/src/helpers/register.ts - Event listener registration

Comparison with Other Services

Other Firebase services like AppCheckService properly clean up their resources in _delete() methods by removing listeners and clearing state.

Proposed Solution

Implement proper resource cleanup in MessagingService._delete() including:

• Clear logging timers
• Remove event listeners
• Reset all properties to initial state
• Clear message handlers and log events
• Provide cleanup mechanism for registered cleanup functions

Environment

• Firebase JS SDK version: 11.8.1
• Affects both browser and service worker environments

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[looptheloop88]

Hi @shehryar-turing, thanks for the report. Let me bring this matter to the attention of our engineers.

The MessagingService._delete() method only returns promise

firebase-js-sdk/packages/messaging/src/messaging-service.ts

Lines 63 to 65 in d5e5795

	_delete(): Promise<void> {
	return Promise.resolve();
	}

While the AppCheckService._delete() method, for comparison, has implementation to remove listeners and clear states

firebase-js-sdk/packages/app-check/src/factory.ts

Lines 38 to 45 in d5e5795

	_delete(): Promise<void> {
	const { tokenObservers } = getStateReference(this.app);
	for (const tokenObserver of tokenObservers) {
	removeTokenListener(this.app, tokenObserver.next);
	}
	return Promise.resolve();
	}
	}