Error on startup using Kakoune and kak-lsp

[raiguard]

I have not yet determined if this bug is the server's fault or the fault of kak-lsp, but I'm trying here first.

Describe the bug
I am using this language server with Kakoune and kak-lsp, and am experiencing an error and disconnect on startup. This error is not shown by kak-lsp, but is only observable in the log file.

Here is the complete log file:

Log file

[10:41:20.508][info] [#0:main:51]: Lua Lsp startup, root: 	/home/rai/dev/langservers/sumneko-lua
[10:41:20.508][debug][#0:main:52]: ROOT:	/home/rai/dev/langservers/sumneko-lua
[10:41:20.508][debug][#0:main:53]: LOGPATH:	/home/rai/dev/langservers/sumneko-lua/log
[10:41:20.508][debug][#0:main:54]: METAPATH:	/home/rai/dev/langservers/sumneko-lua/meta
[10:41:20.513][info] [#0:script.service.telemetry:16]: Telemetry Token:	4C128984A723FF59
[10:41:20.542][info] [#0:script.pub.pub:48]: Create brave:	1
[10:41:20.542][info] [#0:script.pub.pub:48]: Create brave:	2
[10:41:20.542][info] [#0:script.pub.pub:48]: Create brave:	3
[10:41:20.542][info] [#0:script.pub.pub:48]: Create brave:	4
[10:41:20.542][debug][#0:script.service.service:136]: 
========= Medical Examination Report =========
    --------------- Memory ---------------
        Total: 1.753 MB
        # 00 : 1.753 MB
        # 01 : 0.000 MB
        # 02 : 0.000 MB
        # 03 : 0.000 MB
        # 04 : 0.000 MB
    --------------- Coroutine ---------------
        Total:     0
        Running:   0
        Suspended: 0
        Normal:    0
        Dead:      0
    --------------- Cache ---------------
        Total: 1
        Dead:  0
    --------------- Proto ---------------
        Holdon:   0
        Waiting:  0
==============================================
[10:41:20.573][debug][#0:script.provider.client:32]: Client init	{
    capabilities = {
        textDocument = {
            codeAction = {
                codeActionLiteralSupport = {
                    codeActionKind = {
                        valueSet = {
                            [1] = "quickfix",
                            [2] = "refactor",
                            [3] = "refactor.extract",
                            [4] = "refactor.inline",
                            [5] = "refactor.rewrite",
                            [6] = "source",
                            [7] = "source.organizeImports",
                        },
                    },
                },
                dynamicRegistration = false,
                isPreferredSupport = false,
            },
            codeLens = {
                dynamicRegistration = false,
            },
            colorProvider = {
                dynamicRegistration = false,
            },
            completion = {
                completionItem = {
                    commitCharactersSupport = false,
                    deprecatedSupport = false,
                    documentationFormat = {
                        [1] = "plaintext",
                    },
                    preselectSupport = false,
                    snippetSupport = true,
                },
                completionItemKind = {
                    valueSet = {
                        [01] = 1,
                        [02] = 2,
                        [03] = 3,
                        [04] = 4,
                        [05] = 5,
                        [06] = 6,
                        [07] = 7,
                        [08] = 8,
                        [09] = 9,
                        [10] = 10,
                        [11] = 11,
                        [12] = 12,
                        [13] = 13,
                        [14] = 14,
                        [15] = 15,
                        [16] = 16,
                        [17] = 17,
                        [18] = 18,
                        [19] = 19,
                        [20] = 20,
                        [21] = 21,
                        [22] = 22,
                        [23] = 23,
                        [24] = 24,
                        [25] = 25,
                    },
                },
                contextSupport = false,
                dynamicRegistration = false,
            },
            declaration = {
                dynamicRegistration = false,
                linkSupport = false,
            },
            definition = {
                dynamicRegistration = false,
                linkSupport = false,
            },
            documentHighlight = {
                dynamicRegistration = false,
            },
            documentLink = {
                dynamicRegistration = false,
                tooltipSupport = false,
            },
            documentSymbol = {
                dynamicRegistration = false,
            },
            formatting = {
                dynamicRegistration = false,
            },
            hover = {
                contentFormat = {
                    [1] = "plaintext",
                },
                dynamicRegistration = false,
            },
            implementation = {
                dynamicRegistration = false,
                linkSupport = false,
            },
            onTypeFormatting = {
                dynamicRegistration = false,
            },
            publishDiagnostics = {
                relatedInformation = false,
            },
            rangeFormatting = {
                dynamicRegistration = false,
            },
            references = {
                dynamicRegistration = false,
            },
            rename = {
                dynamicRegistration = false,
                prepareSupport = false,
            },
            semanticHighlightingCapabilities = {
                semanticHighlighting = true,
            },
            semanticTokens = {
                dynamicRegistration = false,
                formats = {
                    [1] = "relative",
                },
                requests = {
                    full = true,
                    range = false,
                },
                tokenModifiers = {
                    [1] = "documentation",
                    [2] = "readonly",
                },
                tokenTypes = {
                    [01] = "string",
                    [02] = "variable",
                    [03] = "comment",
                    [04] = "type",
                    [05] = "enumMember",
                    [06] = "macro",
                    [07] = "namespace",
                    [08] = "parameter",
                    [09] = "function",
                    [10] = "keyword",
                    [11] = "lifetime",
                    [12] = "enum",
                    [13] = "operator",
                },
            },
            signatureHelp = {
                contextSupport = false,
                dynamicRegistration = false,
                signatureInformation = {
                    documentationFormat = {
                        [1] = "plaintext",
                    },
                    parameterInformation = {
                        labelOffsetSupport = false,
                    },
                },
            },
            synchronization = {
                didSave = true,
                dynamicRegistration = false,
                willSave = false,
                willSaveWaitUntil = false,
            },
            typeDefinition = {
                dynamicRegistration = false,
                linkSupport = false,
            },
        },
        window = {
            workDoneProgress = false,
        },
        workspace = {
            applyEdit = false,
            configuration = false,
            didChangeConfiguration = {
                dynamicRegistration = false,
            },
            executeCommand = {
                dynamicRegistration = false,
            },
            symbol = {
                dynamicRegistration = false,
                symbolKind = {
                    valueSet = {
                        [01] = 1,
                        [02] = 2,
                        [03] = 3,
                        [04] = 4,
                        [05] = 5,
                        [06] = 6,
                        [07] = 7,
                        [08] = 8,
                        [09] = 9,
                        [10] = 10,
                        [11] = 11,
                        [12] = 12,
                        [13] = 13,
                        [14] = 14,
                        [15] = 15,
                        [16] = 16,
                        [17] = 17,
                        [18] = 18,
                        [19] = 19,
                        [20] = 20,
                        [21] = 21,
                        [22] = 22,
                        [23] = 23,
                        [24] = 24,
                        [25] = 25,
                        [26] = 26,
                    },
                },
            },
            workspaceEdit = {
                changeAnnotationSupport = {
                },
                documentChanges = true,
                failureHandling = "abort",
                normalizesLineEndings = false,
                resourceOperations = {
                    [1] = "create",
                    [2] = "delete",
                    [3] = "rename",
                },
            },
            workspaceFolders = false,
        },
    },
    clientInfo = {
        name = "kak-lsp",
        version = "9.0.0-snapshot",
    },
    processId = 20736,
    rootPath = "/home/rai/dev/projects/personal/Factorio-RecipeBook",
    rootUri = "file:///home/rai/dev/projects/personal/Factorio-RecipeBook",
    trace = "off",
}
[10:41:20.573][info] [#0:script.language:135]: VSC language: nil
[10:41:20.573][info] [#0:script.language:136]: LS  language: en-us
[10:41:20.584][info] [#0:script.workspace.workspace:31]: Workspace inited: 	file:///home/rai/dev/projects/personal/Factorio-RecipeBook
[10:41:20.584][info] [#0:script.workspace.workspace:38]: Log path: 	/home/rai/dev/langservers/sumneko-lua/log/file_home_rai_dev_projects_personal_Factorio-RecipeBook.log
[10:41:20.585][warn] [#0:script.pub.report:24]: Load proto error:	Disconnected!

To Reproduce
Steps to reproduce the behavior:

1. Install Kakoune and kak-lsp via the links above
2. Set up kak-lsp.toml like so (change paths accordingly):

[language.lua]
filetypes = ["lua"]
roots = [".git/"]
command = "/home/rai/dev/langservers/sumneko-lua/bin/lua-language-server"
args = ["-E", "/home/rai/dev/langservers/sumneko-lua/main.lua"]

3. Open a Lua file in Kakoune and enable the language server with :lsp-enable-window
4. Observe that nothing happens
5. Open the log file and observe the error there

Expected behavior
The language server would start up and provide diagnostics.

Screenshots
There should be a syntax error here, but nothing happens:

Environment

• OS: Zorin OS 15 (Ubuntu 18.04)
• Client: Kakoune with kak-lsp

[sumneko]

LSP requires the client to open the standard input and standard output of the server for data exchange. From the log, the standard input was closed for some reason. The server recorded this exception, indicating that the server did not crash at least, so I tended to be a client-side problem.

[raiguard]

Alright, thanks, I'll open an issue with kak-lsp. I'll keep this issue open just in case action is needed on this end.

[raiguard]

See here. I looked into it myself and came to the same conclusion: the language server is returning a value that is out-of-spec, which is causing kak-lsp to panic. It does the same thing with the args set correctly, as in my first post.

[raiguard]

So, any idea why the server would be providing an out-of-spec workspace object?

[raiguard]

I looked into it deeper, and it appears that the server is providing an empty array for the workspace field in the ServerCapabilities object. That field should be an object instead, or if it's empty, shouldn't be provided at all. This is why kak-lsp is crashing, because it's simply the incorrect type.

Here is the spec from the LSP page:

/**
 * Workspace specific server capabilities
 */
workspace?: {
    /**
     * The server supports workspace folder.
     *
     * @since 3.6.0
     */
    workspaceFolders?: WorkspaceFoldersServerCapabilities;

    /**
     * The server is interested in file notifications/requests.
     *
     * @since 3.16.0
     */
    fileOperations?: {
        // snip
    }
}

And here is what kak-lsp is receiving:

"workspace": Array([]),

[raiguard]

Thank you for the fix!