VS Code Extension ↔ Language Server: Workspace Folder Closure Timing

Lifecycle Management of the LanguageClient

VS Code does not automatically dispose of a LanguageClient instance when a workspace folder is closed. The responsibility for managing the client's lifecycle rests entirely with the extension developer. If you do not explicitly call .dispose(), the client remains active in the extension host, and the associated language server process may continue to run in the background until the entire window is reloaded or the extension is deactivated.

Resource Cleanup and Trigger Events

Because the LanguageClient is an object managed by the extension host, its cleanup is tied to the extension's lifecycle rather than the workspace's state. The following conditions trigger resource reclamation:

• Explicit Disposal: Calling client.dispose() sends the LSP shutdown request followed by an exit notification, ensuring a graceful termination of the server.
• Extension Deactivation: When the extension is disabled or the window is closed, the extension host terminates the extension's process and attempts to kill orphaned child processes.
• Window Reload: A full reload kills the current extension host process, which forcibly terminates any server processes linked via stdio.

Implementation for Multi-Root Workspaces

In multi-root environments, closing one folder does not necessarily mean the server should be shut down if other folders of the same language are still open. To handle this, extensions should monitor workspace changes rather than relying on automatic disposal.

To customize this behavior, use the vscode.workspace.onDidChangeWorkspaceFolders event to detect when a folder is removed and determine if the server should be disposed of or simply notified to clear its internal cache for that specific path.

Verification and Diagnostics

To verify if your server is leaking after a folder closure, you can use the following methods:

1. Process Monitoring: Use ps aux | grep [server-name] (Linux/macOS) or Task Manager (Windows) to check if the server process persists after the folder is closed.
2. Server Logging: Implement a log entry within the server's shutdown handler. If the log does not trigger upon folder closure, the client was not disposed.
3. Host Memory: Open the Extension Host process in the VS Code Process Explorer (Help > Open Process Explorer) to monitor memory growth across multiple open/close cycles.

Diagnostic Requirement: To provide a more specific implementation pattern, please specify if your server uses stdio or TCP transport, as TCP servers are more prone to becoming "zombie" processes if the client is not disposed of correctly.