splice(indexOf()) without -1 guard silently removes wrong array element in 4 locations

[SebTardif]

Does this issue occur when all extensions are disabled?: Yes

• VS Code Version: 1.120.0 (main branch, commit 89fc639)
• OS Version: All platforms

Bug

Multiple locations in the codebase use the pattern array.splice(array.indexOf(item), 1) without checking whether indexOf returned -1. When the element is not found, indexOf returns -1, and splice(-1, 1) silently removes the last element of the array instead of being a no-op.

This causes incorrect behavior: the wrong keyboard layout, activity badge, progress indicator, or settings entry is silently removed.

Affected locations

File	Method	Impact
keyboardLayoutService.ts:116-119	removeKeyboardLayout	Removes wrong layout from MRU if called with stale ref
activityService.ts:95, 158	showViewContainerActivity / showActivity dispose callback	Removes wrong activity badge on double dispose
progressService.ts:135	withWindowProgress finally block	Removes wrong progress task if promise resolved before delay
settingsTree.ts:2871	ApplySettingToAllProfilesAction.run	Removes wrong setting from all-profiles list (TOCTOU between this.checked and fresh getValue())

Steps to Reproduce

activityService.ts (double dispose scenario):

1. Register a view container activity via showViewContainerActivity
2. Store the returned IDisposable
3. Call .dispose() on it twice
4. On the second call, indexOf returns -1 because the activity was already removed
5. splice(-1, 1) removes the last activity in the array (belonging to a different view container)
6. The wrong activity badge disappears from the UI

settingsTree.ts (TOCTOU scenario):

1. Open Settings UI
2. Toggle "Apply Setting to All Profiles" for a setting
3. If another VS Code window or process removes that setting from the configurationService.allProfiles list between the this.checked guard (set via config listener) and the getValue() call, indexOf returns -1
4. splice(-1, 1) removes the last entry in the all-profiles list (a different setting)

Fix

A PR is available: #314635

The fix adds index !== -1 guards before each splice call. This is a standard defensive pattern with zero cost.