#+TITLE: Language Server Protocol
#+AUTHOR: Christopher James Hayward
#+EMAIL: chris@chrishayward.xyz

#+PROPERTY: header-args:emacs-lisp :tangle lsp.el :comments org
#+PROPERTY: header-args:shell      :tangle no
#+PROPERTY: header-args            :results silent :eval no-export :comments org

#+OPTIONS: num:nil toc:nil todo:nil tasks:nil tags:nil
#+OPTIONS: skip:nil author:nil email:nil creator:nil timestamp:nil

The Language Server Protocol (LSP) defines the protocol used between an editor, or IDE, and a language server that provides language features like auto-complete, go-to-definition, find-all-references, etc[fn:1]

* Config

Support for the Language Server Protocol[fn:1] is available through the ~lsp-mode~[fn:2] package. Configure an immutable delay of =.5= to ensure it doesn't attack the current language server and overload it with requests.

#+begin_src emacs-lisp
(use-package lsp-mode
  :commands (lsp lsp-deferred)
  :custom (lsp-idle-delay 0.5)
          (lsp-prefer-flymake t))
#+end_src

** Code snippets

Download ~yasnippet~[fn:4], used by a number of ~lsp-mode~[fn:2] extensions to provide smart completion functionality.

#+begin_src emacs-lisp
(use-package yasnippet
  :ensure t)
#+end_src

** UI integration

Download ~lsp-ui~[fn:3] to provide user interface improvements for ~lsp-mode~[fn:2] over the defaults.

#+begin_src emacs-lisp
(use-package lsp-ui
  :after lsp
  :custom (lsp-ui-doc-position 'at-point)
          (lsp-ui-doc-delay 0.500))
#+end_src

** Code completion

Text completion provided by ~company~[fn:5], AKA Complete Anything. Make sure it's integrated with ~lsp-mode~[fn:2] to provide completion candidates through the Language Server Protocol[fn:1].

#+begin_src emacs-lisp
(use-package company
  :after lsp)
#+end_src

Specify the repository for ~company-lsp~ using straight to make sure we're getting the most recent version from GitHub, instead of the typically outdated versions in the Emacs package repositories.

#+begin_src emacs-lisp
(use-package company-lsp
  :after (lsp company)
  :custom (company-lsp-async t)
          (company-backend 'company-lsp)
  :straight (company-lsp :type git
                         :host github
                         :repo "tigersoldier/company-lsp"))
#+end_src

* Footnotes

[fn:1] https://microsoft.github.io/language-server-protocol/

[fn:2] https://emacs-lsp.github.io/lsp-mode/

[fn:3] https://emacs-lsp.github.io/lsp-ui/

[fn:4] https://github.com/joaotavora/yasnippet

[fn:5] https://company-mode.github.io/