fix: guard _resolveGitState against undefined gitRepository (fixes #316425)

[vs-code-engineering]

🔧 Error Fix

Summary

Error: TypeError: Cannot read properties of undefined (reading 'read') in githubService.ts:108 inside a derived observable computation.

The crash occurs when LocalNewSession._resolveGitState() spreads this.sessionWorkspace.folders[0].gitRepository! while gitRepository is undefined. The spread of undefined produces an object missing gitHubInfo, so when the observable chain propagates to the derived in githubService.ts:108, gitHubInfo.read(reader) throws because gitHubInfo is undefined.

This is a new regression in 1.121.0-insider, introduced when gitRepository was made optional on ISessionWorkspaceFolder (commit 1e8d5efd — "sessions: refactor ISession workspace model").

Fixes #316425
Recommended reviewer: @sandy081

Culprit Commit

1e8d5efd by @sandy081

Code Flow

graph TD
    A["$onDidChangeRepository / updateState"] --> B["observable.set() propagation"]
    B --> C["LocalNewSession._resolveGitState autorun"]
    C --> D["...folders[0].gitRepository! — gitRepository is undefined"]
    D --> E["Spread produces object WITHOUT gitHubInfo"]
    E --> F["_workspaceData.set() triggers derived chain"]
    F --> G["githubService.ts:108 — gitHubInfo.read(reader) → TypeError"]

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Affected Files

File	Role
copilotChatSessionsProvider.ts	Producer — _resolveGitState() spreads undefined gitRepository
githubService.ts	Crash site — derived reads gitHubInfo.read(reader) on malformed object

How the Fix Works

Added an early guard in _resolveGitState() to return immediately when folder.gitRepository is undefined. This fixes the bug at the data producer, not the crash site. The ! non-null assertion is removed since the guard ensures gitRepository is always defined when the spread executes.

Recommended Owner

@sandy081

errors-fix-driver — cycle 6

Trigger: cron_merge_conflict · Head: 4a1a5cddde8ab354001e4aff2053c47e7476a34a (4a1a5cd)

Item	Action
Merge conflict in copilotChatSessionsProvider.ts	Resolved — accepted main (class removed upstream)

Push: yes — 4a1a5cd · Copilot rerequested: not applicable (PR has zero diff)

Ready gate: not marking ready — PR now has zero diff against main (LocalNewSession was removed upstream, making this fix moot). Recommend closing this PR as the underlying issue no longer applies.

Generated by errors-fix-driver · ● 32.3M · ◷

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[bryanchen-d]

Closing as superseded. The same null-safety fix for LocalNewSession._resolveGitState already landed via #317645, and the host class was subsequently moved out of copilotChatSessionsProvider.ts by #317979, so this branch can no longer be mechanically rebased onto current main. The underlying issue #316425 is resolved.