fix: memory leak in notebook serializer disposal

[Simon Siefke (SimonSiefke)]

Details

Disposing a notebook serializer registration unregisters it from the main thread but leaves the provider in the extension host serializer registry. Old serializers remain there after their notebooks close and can still handle requests using disposed registration handles.

Change

Delete the serializer registry entry before unregistering it from the main thread. Preserve other live serializers and allow operations that already started to finish without restoring the registration.

Before

Registering a serializer, opening and closing its notebook, and disposing the registration 37 times adds 37 old serializers. The extension host registry grows from 2 to 39 provider entries.

After

No more serializer growth is detected in the same 37-cycle test. The registry stays empty at both snapshots and the named growth result is empty. Small unrelated array and object differences remain in the full heap comparison.

Test Video

Seven serializer registration, notebook open/close, and registration disposal cycles.

test.mp4

_{AI disclosure: Model: GPT 6 Astra. Worktime: 32min}

[Copilot]

Copilot review overview

🟢 Approval recommended

The focused lifecycle fix addresses the leak without disrupting in-flight operations and has appropriate regression coverage.

Review effort: Balanced
Findings: None

What changed in this PR

Fixes retained notebook serializers in the extension host after registration disposal.

Changes:

• Removes disposed serializers from the extension-host registry before main-thread unregistration.
• Adds lifecycle, isolation, idempotency, and in-flight operation tests.

File	Description
src/​vs/​workbench/​api/​common/​extHostNotebook.ts	Deletes the serializer registry entry during disposal.
src/​vs/​workbench/​api/​test/​browser/​extHostNotebookSerializer.test.ts	Verifies serializer disposal behavior and request handling.

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[Dmitriy Vasyura (dmitrivMS)]

Simon Siefke (@SimonSiefke) Thank you!