fix: guard selectDropDownContainer.remove() against already-removed node (fixes #315703)

[vs-code-engineering]

🔧 Error Fix

Summary

Error: NotFoundError: Failed to execute 'remove' on 'Element': The node to be removed is no longer a child of this node.

Bucket: 5dab52a4-d055-fd3c-d16c-a042f3d75688

The settings editor triggers cancelSuggesters() on scroll via updateTreeScrollSync(). This hides the context view, which disposes the select box dropdown. The dispose callback calls selectDropDownContainer.remove(). However, a browser blur event (triggered by the same scroll action) can remove the DOM node before the dispose callback runs, causing the NotFoundError.

Fixes #315703
Recommended reviewer: @mrleemurray

Culprit Commit

No specific culprit commit identified. This is a long-standing race condition between browser blur events and the dispose lifecycle of the select box dropdown.

Code Flow

sequenceDiagram
    participant SE as settingsEditor2
    participant ST as settingsTree
    participant CV as contextViewService
    participant SB as selectBoxCustom
    participant DOM as Browser DOM
    SE->>ST: cancelSuggesters()
    ST->>CV: hideContextView()
    CV->>SB: dispose()
    Note over DOM: blur event already removed the node
    SB->>DOM: selectDropDownContainer.remove()
    DOM-->>SB: NotFoundError!

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Affected Files

File	Role
src/vs/base/browser/ui/selectBox/selectBoxCustom.ts	Crash site
src/vs/workbench/contrib/preferences/browser/settingsEditor2.ts	Triggers scroll sync
src/vs/workbench/contrib/preferences/browser/settingsTree.ts	Calls hideContextView()

How the Fix Works

Chosen approach (src/vs/base/browser/ui/selectBox/selectBoxCustom.ts:531): Added a parentNode guard before calling .remove(). The producer of the invalid state is the browser blur event handler which removes the DOM node before our dispose runs. We cannot prevent the browser behavior, so a guard clause is the correct fix - it prevents the error without hiding any bug.

Recommended Owner

@mrleemurray - recent owner of selectBoxCustom.ts

errors-fix-driver — cycle 25

Trigger: cron_review_comments · Head: 4a85d016b2b0978c04890e5b677dd86f2d74135f (4a85d01)

Item	Action
CI (25/25 checks)	All passing ✅
Review threads	None unresolved
Merge state	blocked (awaiting approval)

Push: no — no code changes needed · Copilot rerequested: no (no push)

Ready gate: CI green. No unresolved threads. PR is not draft. Awaiting human approval from @mrleemurray.

errors-fix-driver — cycle 26

Trigger: cron_review_comments · Head: 4a85d016b2b0978c04890e5b677dd86f2d74135f (4a85d01)

Item	Action
CI (25/25 checks)	All passing ✅
Review threads	None unresolved
Merge state	blocked (awaiting approval)

Push: no — no code changes needed · Copilot rerequested: no (no push)

Ready gate: CI green. No unresolved threads. PR is not draft. Awaiting human approval from @mrleemurray.

errors-fix-driver — cycle 27

Trigger: cron_review_comments · Head: 4a85d016b2b0978c04890e5b677dd86f2d74135f (4a85d01)

Item	Action
CI (25/25 checks)	All passing ✅
Review threads	None unresolved
Merge state	blocked (awaiting approval)

Push: no — no code changes needed · Copilot rerequested: no (no push)

Ready gate: CI green. No unresolved threads. PR is not draft. Awaiting human approval from @mrleemurray.

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