Server shutting down after sending textDocument/hover

[JoeDinn]

I am trying to implement a language server with a vscode extension

Currently all I amtrying to get working is hover
The initialisation messages seem to be working but when the client sends the hover message the client errors:

[Error - 7:08:38 PM] Stopping server failed
Error: Stopping the server timed out
at /path/to/extension/client/node_modules/vscode-languageclient/lib/common/client.js:933:23

This is the response we send:
"Content-Length: 104\r\n\r\n{"jsonrpc":"2.0","id":1,"result":{"contents":{"value":"Showing help text for\nnil","kind":"plaintext"}}}"

but it doesn't get logged in the trace
My guess is that it's taking too long to recieve the response and assuming that the server is down - is there a way of checking this or increasing the timeout?

Here are the messages sent and recieved by the client:

`[Trace - 7:08:07 PM] Sending request 'initialize - (0)'.
Params: {
"processId": 2961119,
"clientInfo": {
"name": "Visual Studio Code",
"version": "1.96.2"
},
"locale": "en",
"rootPath": "/path/to/workspace",
"rootUri": "file:///path/to/workspace",
"capabilities": {
"workspace": {
"applyEdit": true,
"workspaceEdit": {
"documentChanges": true,
"resourceOperations": [
"create",
"rename",
"delete"
],
"failureHandling": "textOnlyTransactional",
"normalizesLineEndings": true,
"changeAnnotationSupport": {
"groupsOnLabel": true
}
},
"configuration": true,
"didChangeWatchedFiles": {
"dynamicRegistration": true,
"relativePatternSupport": true
},
"symbol": {
"dynamicRegistration": true,
"symbolKind": {
"valueSet": [
1,
2,
3,
4,
5,
6,
7,
8,
9,
10,
11,
12,
13,
14,
15,
16,
17,
18,
19,
20,
21,
22,
23,
24,
25,
26
]
},
"tagSupport": {
"valueSet": [
1
]
},
"resolveSupport": {
"properties": [
"location.range"
]
}
},
"codeLens": {
"refreshSupport": true
},
"executeCommand": {
"dynamicRegistration": true
},
"didChangeConfiguration": {
"dynamicRegistration": true
},
"workspaceFolders": true,
"semanticTokens": {
"refreshSupport": true
},
"fileOperations": {
"dynamicRegistration": true,
"didCreate": true,
"didRename": true,
"didDelete": true,
"willCreate": true,
"willRename": true,
"willDelete": true
},
"inlineValue": {
"refreshSupport": true
},
"inlayHint": {
"refreshSupport": true
},
"diagnostics": {
"refreshSupport": true
}
},
"textDocument": {
"publishDiagnostics": {
"relatedInformation": true,
"versionSupport": false,
"tagSupport": {
"valueSet": [
1,
2
]
},
"codeDescriptionSupport": true,
"dataSupport": true
},
"synchronization": {
"dynamicRegistration": true,
"willSave": true,
"willSaveWaitUntil": true,
"didSave": true
},
"completion": {
"dynamicRegistration": true,
"contextSupport": true,
"completionItem": {
"snippetSupport": true,
"commitCharactersSupport": true,
"documentationFormat": [
"markdown",
"plaintext"
],
"deprecatedSupport": true,
"preselectSupport": true,
"tagSupport": {
"valueSet": [
1
]
},
"insertReplaceSupport": true,
"resolveSupport": {
"properties": [
"documentation",
"detail",
"additionalTextEdits"
]
},
"insertTextModeSupport": {
"valueSet": [
1,
2
]
},
"labelDetailsSupport": true
},
"insertTextMode": 2,
"completionItemKind": {
"valueSet": [
1,
2,
3,
4,
5,
6,
7,
8,
9,
10,
11,
12,
13,
14,
15,
16,
17,
18,
19,
20,
21,
22,
23,
24,
25
]
},
"completionList": {
"itemDefaults": [
"commitCharacters",
"editRange",
"insertTextFormat",
"insertTextMode"
]
}
},
"hover": {
"dynamicRegistration": true,
"contentFormat": [
"markdown",
"plaintext"
]
},
"signatureHelp": {
"dynamicRegistration": true,
"signatureInformation": {
"documentationFormat": [
"markdown",
"plaintext"
],
"parameterInformation": {
"labelOffsetSupport": true
},
"activeParameterSupport": true
},
"contextSupport": true
},
"definition": {
"dynamicRegistration": true,
"linkSupport": true
},
"references": {
"dynamicRegistration": true
},
"documentHighlight": {
"dynamicRegistration": true
},
"documentSymbol": {
"dynamicRegistration": true,
"symbolKind": {
"valueSet": [
1,
2,
3,
4,
5,
6,
7,
8,
9,
10,
11,
12,
13,
14,
15,
16,
17,
18,
19,
20,
21,
22,
23,
24,
25,
26
]
},
"hierarchicalDocumentSymbolSupport": true,
"tagSupport": {
"valueSet": [
1
]
},
"labelSupport": true
},
"codeAction": {
"dynamicRegistration": true,
"isPreferredSupport": true,
"disabledSupport": true,
"dataSupport": true,
"resolveSupport": {
"properties": [
"edit"
]
},
"codeActionLiteralSupport": {
"codeActionKind": {
"valueSet": [
"",
"quickfix",
"refactor",
"refactor.extract",
"refactor.inline",
"refactor.rewrite",
"source",
"source.organizeImports"
]
}
},
"honorsChangeAnnotations": false
},
"codeLens": {
"dynamicRegistration": true
},
"formatting": {
"dynamicRegistration": true
},
"rangeFormatting": {
"dynamicRegistration": true
},
"onTypeFormatting": {
"dynamicRegistration": true
},
"rename": {
"dynamicRegistration": true,
"prepareSupport": true,
"prepareSupportDefaultBehavior": 1,
"honorsChangeAnnotations": true
},
"documentLink": {
"dynamicRegistration": true,
"tooltipSupport": true
},
"typeDefinition": {
"dynamicRegistration": true,
"linkSupport": true
},
"implementation": {
"dynamicRegistration": true,
"linkSupport": true
},
"colorProvider": {
"dynamicRegistration": true
},
"foldingRange": {
"dynamicRegistration": true,
"rangeLimit": 5000,
"lineFoldingOnly": true,
"foldingRangeKind": {
"valueSet": [
"comment",
"imports",
"region"
]
},
"foldingRange": {
"collapsedText": false
}
},
"declaration": {
"dynamicRegistration": true,
"linkSupport": true
},
"selectionRange": {
"dynamicRegistration": true
},
"callHierarchy": {
"dynamicRegistration": true
},
"semanticTokens": {
"dynamicRegistration": true,
"tokenTypes": [
"namespace",
"type",
"class",
"enum",
"interface",
"struct",
"typeParameter",
"parameter",
"variable",
"property",
"enumMember",
"event",
"function",
"method",
"macro",
"keyword",
"modifier",
"comment",
"string",
"number",
"regexp",
"operator",
"decorator"
],
"tokenModifiers": [
"declaration",
"definition",
"readonly",
"static",
"deprecated",
"abstract",
"async",
"modification",
"documentation",
"defaultLibrary"
],
"formats": [
"relative"
],
"requests": {
"range": true,
"full": {
"delta": true
}
},
"multilineTokenSupport": false,
"overlappingTokenSupport": false,
"serverCancelSupport": true,
"augmentsSyntaxTokens": true
},
"linkedEditingRange": {
"dynamicRegistration": true
},
"typeHierarchy": {
"dynamicRegistration": true
},
"inlineValue": {
"dynamicRegistration": true
},
"inlayHint": {
"dynamicRegistration": true,
"resolveSupport": {
"properties": [
"tooltip",
"textEdits",
"label.tooltip",
"label.location",
"label.command"
]
}
},
"diagnostic": {
"dynamicRegistration": true,
"relatedDocumentSupport": false
}
},
"window": {
"showMessage": {
"messageActionItem": {
"additionalPropertiesSupport": true
}
},
"showDocument": {
"support": true
},
"workDoneProgress": true
},
"general": {
"staleRequestSupport": {
"cancel": true,
"retryOnContentModified": [
"textDocument/semanticTokens/full",
"textDocument/semanticTokens/range",
"textDocument/semanticTokens/full/delta"
]
},
"regularExpressions": {
"engine": "ECMAScript",
"version": "ES2020"
},
"markdown": {
"parser": "marked",
"version": "1.1.0"
},
"positionEncodings": [
"utf-16"
]
},
"notebookDocument": {
"synchronization": {
"dynamicRegistration": true,
"executionSummarySupport": true
}
}
},
"trace": "verbose",
"workspaceFolders": [
{
"uri": "file:///path/to/workspace,
"name": "test"
}
]
}

[Trace - 7:08:14 PM] Received response 'initialize - (0)' in 7018ms.
Result: {
"capabilities": {
"hoverProvider": "true"
}
}

[Trace - 7:08:14 PM] Sending notification 'initialized'.
Params: {}

[Trace - 7:08:35 PM] Sending request 'textDocument/hover - (1)'.
Params: {
"textDocument": {
"uri": "file:///path/to/document.ext"
},
"position": {
"line": 4,
"character": 9
}
}

[Error - 7:08:36 PM] Client Skill Language Server: connection to server is erroring. Shutting down server.
[Trace - 7:08:36 PM] Sending request 'shutdown - (2)'.
[Trace - 7:08:37 PM] Sending notification '$/cancelRequest'.
Params: {
"id": 1
}

`

[dbaeumer]

Hard to say. Have you tried to debug the server. Errors like this occur when the server for some reason closes the connection or the connection gets lost otherwise.

[JoeDinn]

How can the server close the connection? What sort of thing should I be looking for when debugging? Is there any way to get more info from the client about why the connection is erroring?

[rcjsuen]

My guess is that it's taking too long to recieve the response and assuming that the server is down - is there a way of checking this or increasing the timeout?

I am not sure that "taking a long time" would cause VS Code to terminate your server. Have you tried changing your textDocument/hover handler on the server to just return immediately instead of doing whatever calculations it needs to perform to validate your hypothesis?

[JoeDinn]

Have you tried changing your textDocument/hover handler on the server to just return immediately instead of doing whatever calculations it needs to perform to validate your hypothesis?

I tried putting some timestamps in and it seems to be sending the response almost instantly so that probably isn't the problem

What kinds of things do you think could cause the client to terminate the server? Would it do so if it got an invalid response?

[rcjsuen]

What kinds of things do you think could cause the client to terminate the server? Would it do so if it got an invalid response?

Perhaps you could start by putting a breakpoint here to try and see what's going on.

[JoeDinn]

Perhaps you could start by putting a breakpoint here to try and see what's going on.

I was able to find the problem by breaking here, thanks!

The way we are sending the jsonrpc responses adds a newline to the end of the message but this isn't accounted for when we calculate the content message length so the \n is left in the buffer and gets added to the next response, which breaks it because the client is looking for "content-length" not "\ncontent-length". It supposedly throws the error "Header must provide a Content-length property" but I never saw this anywhere - where should it be dumped to?

Can I suggest that when it errors in this way it dumps the whole response string it recieved to the console? It would have made the debugging much simpler. Until putting the breakpoint in I didn't even know if it had received the response or not. I would have thought writing slightly wrong responses is one of the most common ways for a language server to fail so it would be nice for the client to be looking out for that and giving a more helpful message than just that the connection is erroring

Thanks again for your help!

[rcjsuen]

Can I suggest that when it errors in this way it dumps the whole response string it recieved to the console? It would have made the debugging much simpler.

I imagine this isn't the first time this has happened to someone. I can't comment on this as I'm not a maintainer of this project.

[dbaeumer]

Actually the error message should be logged here: https://github.com/microsoft/vscode-languageserver-node/blob/main/client/src/common/client.ts#L1823

Did you not see the text in the output panel of the LSP client instance?