fix: handle dangling promise rejection in external ingest upload (fixes #317056)

[vs-code-engineering]

🔧 Error Fix

Summary

Error: Ingest not found (404) for document — an unhandled promise rejection from the external ingest upload pool in the Copilot extension's workspace chunk search.

Root Cause: In externalIngestClient.ts, when a document upload returns HTTP 404, the code throws at line 425. The upload promise p is correctly tracked in the uploading set and handled via Promise.all(uploading). However, p.finally(...) (line 432) creates a new promise whose rejection is never caught. When p rejects, the .finally() return promise also rejects — and since no handler is attached to it, Node.js fires an unhandledRejection event that reaches error telemetry.

Fixes #317056
Recommended reviewer: @mjbvz

Culprit Commit

Field	Value
Commit	5137aa4525bcdef5f337d85e9f0078a26ae62585
Author	@mjbvz
Message	Cancel external ingest upload on 404 (num 4211)
Why	This commit introduced the throw on 404 at line 425, which rejects promise p. Combined with the pre-existing p.finally(...) pattern that discards its return value, this created a dangling rejected promise.

Code Flow

sequenceDiagram
    participant PI as performIngestion
    participant IIFE as uploadIIFE
    participant FIN as finallyReturn
    participant PA as PromiseAll
    participant TEL as Telemetry

    PI->>IIFE: start upload
    IIFE->>IIFE: makeRequest returns 404
    IIFE->>IIFE: throw ExternalIngestRequestError line 425
    IIFE-->>FIN: finally callback runs rejected promise
    IIFE-->>PA: rejection propagates via uploading set
    FIN-->>TEL: unhandled rejection no catch on finally return

Loading

Affected Files

File	Role
extensions/copilot/src/platform/workspaceChunkSearch/node/codeSearch/externalIngestClient.ts	Contains the upload promise pool with the dangling .finally()

Repro Steps

1. Open a workspace with Copilot external ingest enabled
2. The backend ingest endpoint returns 404 for a document (e.g., expired ingest session)
3. The 404 triggers the throw at line 425, rejecting promise p
4. p.finally(...) propagates the rejection to its return promise
5. Since the .finally() return is never caught, an unhandled rejection fires

How the Fix Works

Chosen approach (externalIngestClient.ts): Added .catch(() => {}) to the end of the p.finally(...) chain. This prevents the dangling promise from firing an unhandled rejection. The actual error is still correctly propagated via Promise.all(uploading) through the original p reference in the uploading set — the fix is at the data producer of the unhandled rejection (the uncaught .finally() return), not at the crash site.

Recommended Owner

@mjbvz — author of the culprit commit and primary maintainer of the external ingest client.

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