I broke up with neovim....vim is my best friend now

dot_vim/plugged/ale/ale_linters/dart/language_server.vim

@@ -0,0 +1,20 @@
+" Author: aurieh <me@aurieh.me>
+" Description: A language server for dart
+
+call ale#Set('dart_language_server_executable', 'dart_language_server')
+
+function! ale_linters#dart#language_server#GetProjectRoot(buffer) abort
+    " Note: pub only looks for pubspec.yaml, there's no point in adding
+    " support for pubspec.yml
+    let l:pubspec = ale#path#FindNearestFile(a:buffer, 'pubspec.yaml')
+
+    return !empty(l:pubspec) ? fnamemodify(l:pubspec, ':h:h') : ''
+endfunction
+
+call ale#linter#Define('dart', {
+\   'name': 'language_server',
+\   'lsp': 'stdio',
+\   'executable': {b -> ale#Var(b, 'dart_language_server_executable')},
+\   'command': '%e',
+\   'project_root': function('ale_linters#dart#language_server#GetProjectRoot'),
+\})