LSP request cancellation seems to be causing server crashes with v0.57.0

[razzmatazz]

Started happening with v0.57.0

The cause seems to be cancelation requests ($/cancelRequest) from LSP client. This basically makes v0.57.0 unusable on emacs as emacs/lsp-mode actively cancels requests when things come out of view and results are not needed anymore or UI actions are cancelled by user directly.

I have this on my LSP trace log:

[Trace - 08:59:17 PM] Sending request 'textDocument/codeAction - (155)'.
Params: {
  "textDocument": {
    "uri": "file:///Users/bob/src/csharp-language-server/src/CSharpLanguageServer/Server.fs"
  },
  "range": {
    "start": {
      "line": 312,
      "character": 19
    },
    "end": {
      "line": 312,
      "character": 19
    }
  },
  "context": {
    "diagnostics": [
      {
        "range": {
          "start": {
            "line": 312,
            "character": 20
          },
          "end": {
            "line": 314,
            "character": 16
          }
        },
        "severity": 1,
        "code": "10",
        "codeDescription": {
          "href": "https://docs.microsoft.com/en-us/dotnet/fsharp/language-reference/compiler-messages/fs0010"
        },
        "source": "F# Compiler",
        "message": "Incomplete structured construct at or before this point in expression",
        "relatedInformation": []
      }
    ]
  }
}


[Trace - 08:59:17 PM] Received response 'nil - (153)' in 0ms.
Result: {
  "code": -32800,
  "message": "The task was cancelled."
}


[Trace - 08:59:17 PM] Sending notification '$/cancelRequest'.
Params: {
  "id": 155
}

(*CRASH*)

[razzmatazz]

I think this could be related to:

• ionide/LanguageServerProtocol@114bd9c
• RFC: Make JsonRpc to NOT swallow exceptions LanguageServerProtocol#29

..where Ionide.LSP will now crash server on unhandled/unknown exception (TaskCanceledException?) in order to avoid accidentally serializing exception object as a response as per Ionide.LSP#29.

CC @baronfel

[baronfel]

Is this as potentially-simple to fix as adding TaskCanceledException to the set of 'known exceptions' in the IsFatalException check in Ionide.LSP?

[baronfel]

Super weird that this doesn't seem to impact ionide - I've pointed my local ionide at the 0.57.0 FSAC dll and had no change.

[deapsquatter]

Just here to confirm I have the same crash with Emacs with v0.57 as @razzmatazz

[razzmatazz]

not sure if related, but I see that FSAC has downgraded Ionide.LSP to 0.4.4 on this release

[baronfel]

Oh geez, that's probably it then - lost the LSP upgrade on the churn of getting the proj-info dependency updated.

[baronfel]

@razzmatazz wait, I see 0.4.7 of Ionide.LSP in the latest FSAC:

paket.lock:100: Ionide.LanguageServerProtocol (0.4.7)

[razzmatazz]

@razzmatazz wait, I see 0.4.7 of Ionide.LSP in the latest FSAC:

paket.lock100 Ionide.LanguageServerProtocol (0.4.7)

oh right.. sorry, I noticed this commit a8d1172 but not the upgrade one later, sorry

so this is as problem w/ current/master Ionide.LSP

[razzmatazz]

looks good now