LanguageClient

This is a Swift library for abstracting and interacting with language servers that implement the Language Server Protocol. It is built on top of the LanguageServerProtocol library.

Integration

Swift Package Manager

dependencies: [
    .package(url: "https://github.com/ChimeHQ/LanguageClient")
]

Environment

Setting correct environment variables can be critical for a language server. An executable on macOS will not inherent the user’s shell environment. Capturing shell environment variables is tricky business. Despite its name, ProcessInfo.processInfo.userEnvironment captures the process environment, not the user’s.

If you need help here, check out ProcessEnv and ProcessService.

Classes

LocalProcessServer

This class manages a locally-running LSP process.

let params = Process.ExecutionParameters(path: "/path/to/server-executable",
                                         arguments: [],
                                         environment: [])
let processServer = LocalProcessServer(executionParameters: params)
processServer.terminationHandler = { print("server exited") }

// and if you want to observe communications
processServer.logMessages = true

InitializingServer

Server wrapper that provides automatic initialization. This takes care of the protocol initialization handshake, and does so lazily, on first message.

import LanguageClient
import LanguageServerProtocol

let executionParams = Process.ExecutionParameters(path: "/usr/bin/sourcekit-lsp", environment: ProcessInfo.processInfo.userEnvironment)

let localServer = LocalProcessServer(executionParameters: executionParams)

let config = InitializingServer.Configuration(initializeParamsProvider: {
    // you may need to fill in more of the textDocument field for completions
    // to work, depending on your server
    let capabilities = ClientCapabilities(workspace: nil,
                                          textDocument: nil,
                                          window: nil,
                                          general: nil,
                                          experimental: nil)
   
    // pay careful attention to rootPath/rootURI/workspaceFolders, as different servers will
    // have different expectations/requirements here
   
    return InitializeParams(processId: Int(ProcessInfo.processInfo.processIdentifier),
                            locale: nil,
                            rootPath: nil,
                            rootURI: projectURL.absoluteString,
                            initializationOptions: nil,
                            capabilities: capabilities,
                            trace: nil,
                            workspaceFolders: nil)
})
let server = InitializingServer(server: localServer, configuration: config)

let docURL = URL(fileURLWithPath: "/path/to/your/test.swift")
let projectURL = docURL.deletingLastPathComponent()

Task {
    let docContent = try String(contentsOf: docURL)

    let doc = TextDocumentItem(uri: docURL.absoluteString,
                               languageId: .swift,
                               version: 1,
                               text: docContent)
    let docParams = DidOpenTextDocumentParams(textDocument: doc)

    try await server.didOpenTextDocument(params: docParams)

    // make sure to pick a reasonable position within your test document
    let pos = Position(line: 5, character: 25)
    let completionParams = CompletionParams(uri: docURL.absoluteString,
                                            position: pos,
                                            triggerKind: .invoked,
                                            triggerCharacter: nil)
    let completions = try await server.completion(params: completionParams)

    print("completions: ", completions)
}

RestartingServer

Server wrapper that provides transparent server-side state restoration should the underlying process crash.

TextPositionTransformer

A protocol useful for translating between NSRange and LSP’s line-relative positioning system.

FileWatcher

A utility class that uses FS events and glob patterns to handle DidChangeWatchedFiles.

Suggestions or Feedback

We’d love to hear from you! Get in touch via an issue or pull request.

Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms.