Question 1

How do I fix memory leaks from event listeners in TypeScript?

Accepted Answer

Replace raw addEventListener or property handlers like .onclick with addDisposableListener, and register the result via this._register(). For one-time events, wrap the emitter with Event.once() so the listener auto-removes after firing.

Question 2

What is MutableDisposable and when should I use it?

Accepted Answer

MutableDisposable is a container that holds at most one disposable, replacing the previous one when reassigned. Use it in methods called repeatedly, like startSearch(), instead of this._register(), which would accumulate a new listener on every call.

Question 3

How do I detect memory leaks in VS Code extension tests?

Accepted Answer

Call ensureNoDisposablesAreLeakedInTestSuite() at the top of your test suite. It automatically tracks disposables created during tests and fails the suite if any are not disposed, catching leaks before they ship.

Question 4

Why do listeners leak when registered inside repeated method calls?

Accepted Answer

Registering a listener with this._register() inside a method adds it to the class-level store on every invocation, and it is only released when the class is disposed. Use MutableDisposable or return an IDisposable to the caller instead.

Question 5

How do I tie a DisposableStore to a model's lifecycle?

Accepted Answer

Register model.onWillDispose(() => store.dispose()) inside the store itself via store.add(). This guarantees the store and all its listeners are cleaned up exactly when the model is destroyed, preventing orphaned subscriptions.

memory-leak-audit

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