Vim: fix linting of new buffer

In Vim, if the user creates a new buffer with no name, quick-lint-js
searches for a configuration file starting in the parent of the current
working directory. This behavior is unintentional.

Change the Vim plugin to only pass the --path-for-config-search option
for buffers which represent files. THis means that new buffers will
always use the default configuration.

Author: strager

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

@@ -5,7 +5,11 @@
 " https://github.com/dense-analysis/ale
 
 function! quick_lint_js_ale#get_command(buffer_number) abort
-  return '%e --output-format=vim-qflist-json --vim-file-bufnr '.string(a:buffer_number).' --path-for-config-search=%s %t'
+  let l:extra_options = ''
+  if quick_lint_js_ale#is_buffer_associated_with_file(a:buffer_number)
+    let l:extra_options .= ' --path-for-config-search=%s'
+  endif
+  return '%e --output-format=vim-qflist-json --vim-file-bufnr '.string(a:buffer_number).l:extra_options.' %t'
 endfunction
 
 function! quick_lint_js_ale#get_executable(buffer_number) abort
@@ -36,6 +40,11 @@ function! quick_lint_js_ale#get_lsp_project_root(_buffer_number) abort
   return '/'
 endfunction
 
+function! quick_lint_js_ale#is_buffer_associated_with_file(buffer_number) abort
+  return bufname(a:buffer_number) !=# ''
+    \ && getbufvar(a:buffer_number, '&buftype') ==# ''
+endfunction
+
 " quick-lint-js finds bugs in JavaScript programs.
 " Copyright (C) 2020  Matthew "strager" Glazar
 "

plugin/vim/test.vim

@@ -15,6 +15,11 @@ function! s:main() abort
 endfunction
 
 function! s:test_all() abort
+  call s:test_parse_command_output()
+  call s:test_buffer_is_associated_with_file()
+endfunction
+
+function! s:test_parse_command_output() abort
   let l:qflist = s:parse([''])
   call assert_equal([], l:qflist)
 
@@ -72,6 +77,33 @@ function! s:parse(lines) abort
   return quick_lint_js_ale#parse_command_output(0, a:lines)
 endfunction
 
+function! s:test_buffer_is_associated_with_file() abort
+  %bwipeout!
+  call assert_false(quick_lint_js_ale#is_buffer_associated_with_file(bufnr('%')))
+
+  %bwipeout!
+  silent edit file-name.txt
+  call assert_true(quick_lint_js_ale#is_buffer_associated_with_file(bufnr('%')))
+
+  %bwipeout!
+  silent edit file-name.txt
+  set buftype=nofile
+  call assert_false(quick_lint_js_ale#is_buffer_associated_with_file(bufnr('%')))
+
+  %bwipeout!
+  help
+  set filetype=javascript
+  call assert_false(quick_lint_js_ale#is_buffer_associated_with_file(bufnr('%')))
+
+  " Check a buffer different from the current buffer:
+  %bwipeout!
+  silent edit file.txt
+  let l:file_buffer_number = bufnr('%')
+  new
+  call assert_false(quick_lint_js_ale#is_buffer_associated_with_file(bufnr('%')))
+  call assert_true(quick_lint_js_ale#is_buffer_associated_with_file(l:file_buffer_number))
+endfunction
+
 function! s:check_for_errors() abort
   if len(v:errors) > 0
     for l:error in v:errors