[Error] unhandlederror-Throttler is disposed

[vs-code-engineering]

Error Message

unhandlederror-Throttler is disposed

Stack Trace

    at Mu.queue (./src/vs/base/common/async.ts:241:25)
    at i1e.refresh (./src/vs/workbench/contrib/scm/browser/scmHistoryViewPane.ts:1899:0)
    at (anonymous) (./src/vs/workbench/contrib/scm/browser/scmHistoryViewPane.ts:1803:0)
    at cb (./src/vs/base/common/observableInternal/utils/runOnChange.ts:36:3)
    at fn (./src/vs/base/common/observableInternal/reactions/autorun.ts:84:3)
    at NV._run (./src/vs/base/common/observableInternal/reactions/autorunImpl.ts:110:10)
    at NV.endUpdate (./src/vs/base/common/observableInternal/reactions/autorunImpl.ts:167:11)
    at EO.finish (./src/vs/base/common/observableInternal/transaction.ts:102:12)
    at NP.set (./src/vs/base/common/observableInternal/observables/observableValue.ts:77:8)
    at DSi.$onDidChangeHistoryItemRefs (./src/vs/workbench/api/browser/mainThreadSCM.ts:277:30)
    at LSi.$onDidChangeHistoryProviderHistoryItemRefs (./src/vs/workbench/api/browser/mainThreadSCM.ts:579:11)
    at GAt.$onDidChangeHistoryProviderHistoryItemRefs (./src/vs/workbench/api/browser/mainThreadSCM.ts:849:11)

Raw Stack Trace (minified)

Error: Throttler is disposed     at Mu.queue (out/vs/workbench/workbench.desktop.main.js:406:73042)     at i1e.refresh (out/vs/workbench/workbench.desktop.main.js:3883:133918)     at out/vs/workbench/workbench.desktop.main.js:3883:132320     at out/vs/workbench/workbench.desktop.main.js:407:25381     at NV._runFn (out/vs/workbench/workbench.desktop.main.js:407:9361)     at NV._run (out/vs/workbench/workbench.desktop.main.js:407:6694)     at NV.endUpdate (out/vs/workbench/workbench.desktop.main.js:407:7325)     at EO.finish (out/vs/workbench/workbench.desktop.main.js:406:109996)     at NP.set (out/vs/workbench/workbench.desktop.main.js:407:2882)     at DSi.$onDidChangeHistoryItemRefs (out/vs/workbench/workbench.desktop.main.js:1043:4918)     at LSi.$onDidChangeHistoryProviderHistoryItemRefs (out/vs/workbench/workbench.desktop.main.js:1043:10230)     at GAt.$onDidChangeHistoryProviderHistoryItemRefs (out/vs/workbench/workbench.desktop.main.js:1043:14632)

Details

Property	Value
Bucket ID	3f9a44d3-5c9a-13cb-3518-bd753857bcd1
Version	1.118.0-insider
Commit	f2b51f3f
Last Seen	Sun Apr 26 2026 23:11:23 GMT+0000 (Coordinated Universal Time)
Platforms	Mac, Windows, Linux
Product	VSCode

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This issue was automatically created from the VS Code Errors Dashboard

[vs-code-engineering]

Regression Details

• Product: VSCode
• Regression type: new
• Last release without this error: 1.117.0 (10c8e557)
• First release with this error: 1.118.0-insider (102df5b5)
• Commit range: 10c8e557...102df5b5

The Throttler is used after disposal in scmHistoryViewPane.ts. Deminified stack: async.ts:241 (Throttler.queue) → scmHistoryViewPane.ts:1899 (refresh) → observable autorun chain → mainThreadSCM.ts:277 ($onDidChangeHistoryItemRefs).

Additional coalesced bucket: 651541fe (22 users, same scmHistoryViewPane.ts:1899 path via $onDidChangeCurrentHistoryItemRefs) is linked to this issue.

Related closed issues: #240196, #232913, #233158 (all old-format, same SCM Throttler pattern, previously fixed).

Generated by errors-regression-scan · ● 9.6M · ◷

[vs-code-engineering]

🔍 Error Investigation

Summary

The error Throttler is disposed occurs because the async onDidChangeBodyVisibility handler in SCMHistoryViewPane continues executing after the view pane has been disposed. Observable subscriptions added to the already-disposed _visibilityDisposables store are leaked (not cleaned up), so they remain active and call refresh() on the disposed view — where _refreshThrottler.queue() throws because the throttler's cancellation token has already been cancelled. This affects all platforms (Mac, Windows, Linux) with 120 hits / 29 users on 1.118.0-insider.

Culprit Commit

No explicit commit range was provided in the issue body or comments, so a specific culprit commit could not be identified via bisection. However, this error is new to 1.118.0 (not present in 1.117.0). It is a latent lifecycle bug in SCMHistoryViewPane — the async disposal race has likely always been possible, but may have become more frequent due to changes in the 1.118.0 cycle (e.g., PR #311284 which changes SCM source control disposal timing in the extension host).

Code Flow

sequenceDiagram
    participant ExtHost as Extension Host (Git)
    participant MainSCM as mainThreadSCM.ts
    participant Observable as Observable System
    participant ViewPane as SCMHistoryViewPane
    participant Throttler as _refreshThrottler

    Note over ViewPane: View becomes visible →<br/>async handler starts
    ViewPane->>ViewPane: await waitForState(...)
    Note over ViewPane: ⚠️ View pane disposed<br/>while awaiting
    ViewPane->>ViewPane: _visibilityDisposables.dispose()
    ViewPane->>Throttler: super.dispose() → throttler disposed
    Note over ViewPane: await resolves →<br/>handler continues
    ViewPane->>ViewPane: _visibilityDisposables.add(autorun)<br/>⚠️ Store is disposed → autorun LEAKED
    ExtHost->>MainSCM: $onDidChangeHistoryItemRefs
    MainSCM->>Observable: set(_historyItemRefChanges)
    Observable->>ViewPane: runOnChange callback (line 1803)
    ViewPane->>ViewPane: this.refresh()
    ViewPane->>Throttler: _refreshThrottler.queue(...)
    Note over Throttler: 💥 Error: Throttler is disposed<br/>(cancellation token cancelled)

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Affected Files

File	Role
src/vs/workbench/contrib/scm/browser/scmHistoryViewPane.ts	Root cause — async onDidChangeBodyVisibility handler (line 1726) lacks disposal guards; refresh() (line 1898) has no disposal check
src/vs/base/common/lifecycle.ts	DisposableStore.add() on a disposed store leaks the item (line 476-479) rather than disposing it — this enables the leaked subscriptions
src/vs/base/common/async.ts	Crash site — Throttler.queue() (line 240-241) correctly rejects when disposed
src/vs/workbench/api/browser/mainThreadSCM.ts	Data flow — $onDidChangeHistoryItemRefs (line 272) sets the observable that triggers the leaked subscription

Repro Steps

1. Open VS Code Insiders (1.118.0) with a Git repository
2. Open the Source Control Graph view (SCM History)
3. Rapidly toggle the view's visibility (e.g., collapse/expand the panel, switch to another view and back) while the repository has background activity (auto-fetch enabled helps)
4. Close the SCM History view (or the entire panel) while Git is actively fetching — the async handler may still be awaiting waitForState or withProgress
5. When the extension host sends a history item ref change after disposal, the error fires

The race is non-deterministic — it requires the view to be disposed during the async initialization window (between await waitForState at line 1744 and subscription setup completion).

Fix Proposal

Fix location: src/vs/workbench/contrib/scm/browser/scmHistoryViewPane.ts → onDidChangeBodyVisibility handler and refresh()

Approach: Two complementary changes:

1. Guard refresh() against disposal: Add an early return in refresh() if this._store.isDisposed is true, preventing calls to the disposed throttler:

   refresh() → if (this._store.isDisposed) return; before calling _refreshThrottler.queue()
   

2. Make the async handler cancellation-aware: After each await in the onDidChangeBodyVisibility handler (lines 1744 and 1747), check this._store.isDisposed and return early if the view has been disposed. This prevents leaked subscriptions from being created in the first place.

The DisposableStore.add() behavior (leaking on disposed store) is by design as a safety measure — the fix should prevent reaching that code path rather than changing the store's behavior.

Recommended Owner

@lszomoru — SCM area owner per triage/working-areas.md (owns SCM, Git Extension, GitHub Extension)

Generated by errors-investigate · ● 16.6M · ◷