Vim: add LSP client (disabled by default)

Allow Vim+ALE users to opt into using quick-lint-js' LSP server instead
of the inefficient CLI solution. The LSP server is more buggy, so it's
disabled by default.

Author: strager

plugin/vim/quick-lint-js.vim/ale_linters/javascript/quick_lint_js.vim

@@ -7,26 +7,45 @@
 call ale#Set('javascript_quick_lint_js_executable', 'quick-lint-js')
 call ale#Set('javascript_quick_lint_js_use_global', get(g:, 'ale_use_global_executables', 0))
 
+" TODO(strager): Make quick-lint-js-lsp the default when the bugs have been
+" ironed out:
+" https://github.com/quick-lint/quick-lint-js/issues/111
+" https://github.com/quick-lint/quick-lint-js/issues/171
+let s:enable_lsp_linter = v:false
+
 if ale#Has('ale-2.4.0')
   let s:linter_command_callback_key = 'command'
   let s:linter_executable_callback_key = 'executable'
+  let s:linter_project_root_callback_key = 'project_root'
 else
   " The _callback variants are not supported since ALE v3.0.0. For details, see
   " "Implement a uniform API for asynchronous processing for most ALE features":
   " https://github.com/dense-analysis/ale/issues/2132
   let s:linter_command_callback_key = 'command_callback'
   let s:linter_executable_callback_key = 'executable_callback'
+  let s:linter_project_root_callback_key = 'project_root_callback'
 endif
 
-call ale#linter#Define('javascript', {
-  \ 'aliases': ['quick_lint_js', 'quicklintjs'],
-  \ 'callback': function('quick_lint_js_ale#parse_command_output'),
-  \ 'name': 'quick-lint-js',
-  \ 'output_stream': 'stdout',
-  \ 'read_buffer': 0,
-  \ s:linter_command_callback_key: function('quick_lint_js_ale#get_command'),
-  \ s:linter_executable_callback_key: function('quick_lint_js_ale#get_executable'),
-\ })
+if s:enable_lsp_linter
+  call ale#linter#Define('javascript', {
+    \ 'aliases': ['quick-lint-js-lsp', 'quick_lint_js', 'quicklintjs'],
+    \ 'lsp': 'stdio',
+    \ 'name': 'quick-lint-js',
+    \ s:linter_command_callback_key: function('quick_lint_js_ale#get_lsp_command'),
+    \ s:linter_executable_callback_key: function('quick_lint_js_ale#get_executable'),
+    \ s:linter_project_root_callback_key: function('quick_lint_js_ale#get_lsp_project_root'),
+  \ })
+else
+  call ale#linter#Define('javascript', {
+    \ 'aliases': ['quick-lint-js-cli', 'quick_lint_js', 'quicklintjs'],
+    \ 'callback': function('quick_lint_js_ale#parse_command_output'),
+    \ 'name': 'quick-lint-js',
+    \ 'output_stream': 'stdout',
+    \ 'read_buffer': 0,
+    \ s:linter_command_callback_key: function('quick_lint_js_ale#get_command'),
+    \ s:linter_executable_callback_key: function('quick_lint_js_ale#get_executable'),
+  \ })
+endif
 
 " quick-lint-js finds bugs in JavaScript programs.
 " Copyright (C) 2020  Matthew Glazar

plugin/vim/quick-lint-js.vim/autoload/quick_lint_js_ale.vim

@@ -28,6 +28,14 @@ function! quick_lint_js_ale#parse_command_output(buffer, lines) abort
   return l:data.qflist
 endfunction
 
+function! quick_lint_js_ale#get_lsp_command(_buffer_number) abort
+  return '%e --lsp-server'
+endfunction
+
+function! quick_lint_js_ale#get_lsp_project_root(_buffer_number) abort
+  return '/'
+endfunction
+
 " quick-lint-js finds bugs in JavaScript programs.
 " Copyright (C) 2020  Matthew Glazar
 "