What is Language Server Protocol(LSP)?

  • Language Server Protocol defines standardized protocol with which both a text editor or IDE(client) and a language(server) communicate.
  • The protocol is based on JSONRPC.
  • A client(text editor) can implement
    • Go to definition
    • Error and warnings
    • Auto completion
    • …

diagram

https://microsoft.github.io/language-server-protocol/overviews/lsp/overview/

  • Solves m-times-n complexity problems

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What is Sourcekit-LSP?

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  • Apple’s LSP implementation on top of sourcekitd and clangd
  • sourcekitd is a framework that provide IDE features
  • clangd for c-family languages (C/C++/ObjC) language server
  • supports only Swift Package Manager project

As of Xcode 11.4, SourceKit-LSP is a built-in tool.

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/sourcekit-lsp

Xcode and the corresponding Command Line Tools package include the SourceKit-LSP language server for Swift and C-based languages. The language server is in early development, and this is a great time to experiment with it. SourceKit-LSP can be used with third-party tools that support the Language Server Protocol (LSP), and it supports Swift Packages built from the command-line. For information about using SourceKit-LSP see Getting Started with SourceKit-LSP. (48004600)

https://developer.apple.com/documentation/xcode_release_notes/xcode_11_4_release_notes

VSCode Integration

https://github.com/apple/sourcekit-lsp/tree/master/Editors/vscode

$ cd Editors/vscode
$ npm run createDevPackage
$ code --install-extension out/sourcekit-lsp-vscode-dev.vsix
  • VSCode extension isn’t published on marketplace yet.
  • You must build on your own.
  • try alternatives but they need more complex integration

Recap

LSP transforms text editor into IDE

Try writing Swift on

  • VSCode(recommended)
  • Sublime Text
  • Vim
  • Emacs
  • …