Implements utils that can be used to ensure that all disposables are disposed after a test completes

[hediet]

This PR fixes #127250.
As part of this, some disposables that previously were automatically "disposed" by the garbage collector are now disposed explicitly.

Helpers are added to support tests in the following style:

suite('My Suite', () => {
    // Call this helper to ensure that all disposables are disposed after every test in this suite.
    // Internally, setup and teardown are used.
    ensureNoDisposablesAreLeakedInTestSuite();

    test('My Test 1 (succeeds)', () => {
        // This test succeeds, since all disposables are disposed.
        toDisposable(() => { }).dispose();
    });

    test('My Test 2 (fails)', () => {
        // This test fails, as the following disposable leaks.
        toDisposable(() => { });
    });
});

This also applies to event subscriptions that now use toSelfClearingDisposable, which supports tracking.
Use markAsSingleton to exclude disposable singletons (and all its registered children) that are created during the test.

[alexdima]

Any particular reason why toDisposable should not do the same self.dispose = noop ? i.e. shouldn't toDisposable just be toNonLeakingDisposable?

[hediet]

That would change the semantics of toDisposable: Currently, multiple calls of dispose will lead to multiple calls of fn.
With self.dispose = noop, multiple calls of dispose will only call fn once.

I don't know if anyone depends on this behavior.

[alexdima]

cc @jrieken @mjbvz That seems a wrong implementation of toDisposable. Could we try fixing that in the debt week (even outside this PR) to maximize our selfhosting coverage?

[jrieken]

I think @joaomoreno is Mr toDisposable but I agree that this should be called only once

[jrieken]

Tests are all happy, optimistically pushed that: f8cf8f3

[joaomoreno]

I think @joaomoreno is Mr toDisposable but I agree that this should be called only once

As if I would have any reason other than didn't think about that 🤷‍♂️.

Let's have toDisposable do exactly what toNonLeakingDisposable does.

[alexdima]

I could not find a usage of this. Is this needed?

[hediet]

This is needed in inline completions. Currently they use a copy of MutableDisposable that has this method, as I didn't want to be blocked by a code review.

Also, clearAndLeak makes use of the new tracking API (disposables can be removed from parent disposables).

[jrieken]

Not sure why the source is wrapped in a dispo store? Is this to capture the listener from onCancellationRequested? This shouldn't be a problem when the store is always disposed. Btw, this made me realize that there is still a leak here: when cancellation happens (L26/27) the source/disposableStore isn't disposed

[hediet]

Thanks for pointing out the leak!

Is this to capture the listener from onCancellationRequested?

Yes.

This shouldn't be a problem when the store is always disposed.

You are right, it does not need to be disposed here as the disposables inside of CancellationTokenSource are not tracked.
It is very important to always dispose the event subscription though, otherwise the tooling introduced by this PR will recognize that as leak (even though garbage collection does take care of it).

[mjbvz]

LGTM! Thanks for looking into this