Cancelled requests from cpptools server don't throw exceptions in extension host

[benmcmorran]

Environment

• OS and Version: Windows 11
• VS Code Version: 1.93.0
• C/C++ Extension Version: 1.21.6
• If using SSH remote, specify OS of remote machine: N/A

Bug Summary and Steps to Reproduce

If the cpptools server cancels an LSP request, the error information is returned directly as a result instead of propagating as an exception into the extension host. In the screenshot below, I have a dummy LSP handler than always cancels.

The expected behavior when the JSON-RPC message indicates an error is that an exception is thrown, which can then be handled with normal try/catch mechanisms in Typescript.

This is happening because when the cpptools server cancels a request, it puts ResponseError information into the result member of the ResponseMessage. It should actually go into the error member to be correctly handled by vscode-jsonrpc.

Configuration and Logs

N/A

Other Extensions

No response

Additional context

No response