To use Dart’s LSP server with Vim you’ll need to be using at least version 2.2.0 of the Dart SDK (which shipped in version 1.2.1 of Flutter). A Vim plugin manager is not required but may simplify setup. The steps below have been written assuming use of vim-plug.
Install the dart-vim-plugin and vim-lsc plugins. Using vim-plug this can be done by adding the following to .vimrc then reloading and running :PlugInstall:
call plug#begin('~/.vim/plugged')
Plug 'dart-lang/dart-vim-plugin'
Plug 'natebosch/vim-lsc'
call plug#end()
Note: Other LSP plugins are available for Vim but this document assumes vim-lsc.
Next tell vim-lsc how to invoke the LSP server. You’ll need the path to the Dart SDK (which may be inside the Flutter SDK at bin/cache/dart-sdk for Flutter) and add this to .vimrc and reload.
let g:lsc_server_commands = {'dart': '~/dart-sdk/bin/dart ~/dart-sdk/bin/snapshots/analysis_server.dart.snapshot --lsp'}
let g:lsc_auto_map = v:true " Use defaults
This will set up the LSP server for Dart files using default keybindings. More info on configuring vim-lsc can be found at natebosch/vim-lsc#configuration.
Open a Dart file in Vim and confirm that you see syntax highlighting (this is provided by dart-vim-plugin) and that invalid code is highlighted (this is provided by the LSP server via vim-lsc), with the error showing along the bottom of the window.
Keybindings and commands are documented in the vim-lsc README.
Available features are those supported by both the vim-lsc plugin (see here) and the Dart LSP server (see here).
If you find an issue with the LSP server you can enable logging in the server by adding the following switches to the LSP server command in .vimrc:
--instrumentation-log-file /path/to/logs/lsp-vim.txt
Issues should be opened in the dart-lang/sdk repository.