Cannot Initialize Language Server Protocol

Question

I'm toying around LSP and I cannot get past first stage. Am using Python as client language since it is simple to work with. All I do is:

Connect to LSP - This works fine
Send Initialize JSON RPC - Client report success
Get response - Empty result

I have tried everything I could and read whatever I could find but I had no success. I hope for someone more conversant with LSP to help me pointing out what am doing wrong.

Here is my Python code. I tried with PHP Language Server but shouldn't matter the kind of server used.

import socket
import sys 

initReq = """
{
    "jsonrpc": "2.0",
    "id": 1,
    "method": " initialize",
    "params": {
        "processId": null,
        "rootPath": "/Users/stefano/Testing/PHPSources",
        "rootUri": "file:///Users/stefano/Testing/PHPSources",
        "capabilities": {
            "workspace": {
                "applyEdit": true,
                "workspaceEdit": {
                    "documentChanges": true,
                    "resourceOperations": [
                        "create",
                        "rename",
                        "delete"
                    ],
                    "failureHandling": "textOnlyTransactional"
                },
                "didChangeConfiguration": {
                    "dynamicRegistration": true
                },
                "didChangeWatchedFiles": {
                    "dynamicRegistration": 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
                        ]
                    }
                },
                "executeCommand": {
                    "dynamicRegistration": true
                },
                "configuration": true,
                "workspaceFolders": true
            },
            "textDocument": {
                "publishDiagnostics": {
                    "relatedInformation": true,
                    "tagSupport": 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
                    },
                    "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
                        ]
                    }
                },
                "hover": {
                    "dynamicRegistration": true,
                    "contentFormat": [
                        "markdown",
                        "plaintext"
                    ]
                },
                "signatureHelp": {
                    "dynamicRegistration": true,
                    "signatureInformation": {
                        "documentationFormat": [
                            "markdown",
                            "plaintext"
                        ],
                        "parameterInformation": {
                            "labelOffsetSupport": 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
                },
                "codeAction": {
                    "dynamicRegistration": true,
                    "codeActionLiteralSupport": {
                        "codeActionKind": {
                            "valueSet": [
                                "",
                                "quickfix",
                                "refactor",
                                "refactor.extract",
                                "refactor.inline",
                                "refactor.rewrite",
                                "source",
                                "source.organizeImports"
                            ]
                        }
                    }
                },
                "codeLens": {
                    "dynamicRegistration": true
                },
                "formatting": {
                    "dynamicRegistration": true
                },
                "rangeFormatting": {
                    "dynamicRegistration": true
                },
                "onTypeFormatting": {
                    "dynamicRegistration": true
                },
                "rename": {
                    "dynamicRegistration": true,
                    "prepareSupport": true
                },
                "documentLink": {
                    "dynamicRegistration": true
                },
                "typeDefinition": {
                    "dynamicRegistration": true,
                    "linkSupport": true
                },
                "implementation": {
                    "dynamicRegistration": true,
                    "linkSupport": true
                },
                "colorProvider": {
                    "dynamicRegistration": true
                },
                "foldingRange": {
                    "dynamicRegistration": true,
                    "rangeLimit": 5000,
                    "lineFoldingOnly": true
                },
                "declaration": {
                    "dynamicRegistration": true,
                    "linkSupport": true
                }
            }
        },
        "initializationOptions": {
            "storagePath": "/Users/hosanna/Library/Application Support/Code/User/workspaceStorage/30bd6a399166f4f329c9f383d63b74ca/bmewburn.vscode-intelephense-client",
            "clearCache": false
        },
        "trace": "verbose",
        "workspaceFolders": [
            {
                "uri": "file:///Users/stefano/Testing/PHPSources",
                "name": "TransportationApp"
            }
        ]
    }
}
"""

host = '127.0.0.1'
port = 8088

# create socket
print('# Creating socket')
try:
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
except socket.error:
    print('Failed to create socket')
    sys.exit()

# Connect to remote server
print('# Connecting to server, ' + host)
s.connect((host , port))

# Send data to remote server
print('# Sending data to server')

try:
    s.sendall(initReq.encode('utf-8'))
except socket.error:
    print('Send failed')
    sys.exit()

# Receive data
print('# Receive data from server')
reply = s.recv(4096)

print(reply)

Stefano Mtangoo · Accepted Answer · 2019-03-28 17:54:32Z

2

I was missing the header part and its respective new lines. Thanks to rcjsuen for helping on Github

format for reference should be:

Content-Length: <length>\r\n
\r\n
{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "textDocument/didOpen",
    "params": {
        ...
    }
}

answered Mar 28, 2019 at 17:54

Stefano Mtangoo

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7 Comments

K. Symbol Over a year ago

Currently I am wondering if it works to interact with the language server by directly sending JSON RPC. It seems that your code confirms it, but how to generate the valid json for LSP? Can you give me some instructions?

Stefano Mtangoo Over a year ago

LSP uses JSONRPC. You can see the Specs here: jsonrpc.org/specification

Stefano Mtangoo Over a year ago

Then the JSON payloa have to be combined with at least Content-Length header to make a valid Protocol compliant request (as my answer shows

K. Symbol Over a year ago

Thanks for answering, I am trying to generate valid LSP json according to: microsoft.github.io/language-server-protocol/specification , but currently I only managed to send initialize request as your code, did you try other methods (like didOpen/definition)?

Stefano Mtangoo Over a year ago

Yes I did, where do you get a problem? Do you get the response for initialize?

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