Fix #624 - Ask for the Vint version in the background

ale_linters/vim/vint.vim

@@ -4,18 +4,32 @@
 " This flag can be used to change enable/disable style issues.
 let g:ale_vim_vint_show_style_issues =
 \   get(g:, 'ale_vim_vint_show_style_issues', 1)
-
-let s:vint_version = ale#semver#Parse(system('vint --version'))
-let s:can_use_no_color_flag = ale#semver#GreaterOrEqual(s:vint_version, [0, 3, 7])
 let s:enable_neovim = has('nvim') ? ' --enable-neovim ' : ''
 let s:format = '-f "{file_path}:{line_number}:{column_number}: {severity}: {description} (see {reference})"'
 
-function! ale_linters#vim#vint#GetCommand(buffer) abort
+function! ale_linters#vim#vint#VersionCommand(buffer) abort
+    if !exists('s:vint_version')
+        " Check the Vint version if we haven't checked it already.
+        return 'vint --version'
+    endif
+
+    return ''
+endfunction
+
+function! ale_linters#vim#vint#GetCommand(buffer, version_output) abort
+    if !empty(a:version_output)
+        " Parse the version out of the --version output.
+        let s:vint_version = ale#semver#Parse(join(a:version_output, "\n"))
+    endif
+
+    let l:can_use_no_color_flag = exists('s:vint_version')
+    \   && ale#semver#GreaterOrEqual(s:vint_version, [0, 3, 7])
+
     let l:warning_flag = ale#Var(a:buffer, 'vim_vint_show_style_issues') ? '-s' : '-w'
 
     return 'vint '
     \   . l:warning_flag . ' '
-    \   . (s:can_use_no_color_flag ? '--no-color ' : '')
+    \   . (l:can_use_no_color_flag ? '--no-color ' : '')
     \   . s:enable_neovim
     \   . s:format
     \   . ' %t'
@@ -24,6 +38,9 @@ endfunction
 call ale#linter#Define('vim', {
 \   'name': 'vint',
 \   'executable': 'vint',
-\   'command_callback': 'ale_linters#vim#vint#GetCommand',
+\   'command_chain': [
+\       {'callback': 'ale_linters#vim#vint#VersionCommand', 'output_stream': 'stderr'},
+\       {'callback': 'ale_linters#vim#vint#GetCommand', 'output_stream': 'stdout'},
+\   ],
 \   'callback': 'ale#handlers#gcc#HandleGCCFormat',
 \})