Support `python -m flake8` for users who are running flake8 that way

2 files changed, 41 insertions, 3 deletions

diff --git a/ale_linters/python/flake8.vim b/ale_linters/python/flake8.vim
index ab074567..4959583f 100644
--- a/ale_linters/python/flake8.vim
+++ b/ale_linters/python/flake8.vim
@@ -14,8 +14,12 @@ let g:ale_python_flake8_use_global = get(g:, 'ale_python_flake8_use_global', 0)
 " executables, so we don't have to look up the version number constantly.
 let s:version_cache = {}
 
+function! s:UsingModule(buffer) abort
+    return ale#Var(a:buffer, 'python_flake8_options') =~# ' *-m flake8'
+endfunction
+
 function! ale_linters#python#flake8#GetExecutable(buffer) abort
-    if !ale#Var(a:buffer, 'python_flake8_use_global')
+    if !s:UsingModule(a:buffer) && !ale#Var(a:buffer, 'python_flake8_use_global')
         let l:virtualenv = ale#python#FindVirtualenv(a:buffer)
 
         if !empty(l:virtualenv)
@@ -44,8 +48,10 @@ function! ale_linters#python#flake8#VersionCheck(buffer) abort
         return ''
     endif
 
-    return fnameescape(ale_linters#python#flake8#GetExecutable(a:buffer))
-    \   . ' --version'
+    let l:executable = fnameescape(ale_linters#python#flake8#GetExecutable(a:buffer))
+    let l:module_string = s:UsingModule(a:buffer) ? ' -m flake8' : ''
+
+    return l:executable . l:module_string . ' --version'
 endfunction
 
 " Get the flake8 version from the output, or the cache.
diff --git a/test/command_callback/test_flake8_command_callback.vader b/test/command_callback/test_flake8_command_callback.vader
index bf4dfaff..baec5335 100644
--- a/test/command_callback/test_flake8_command_callback.vader
+++ b/test/command_callback/test_flake8_command_callback.vader
@@ -70,3 +70,35 @@ Execute(The flake8 callbacks should detect virtualenv directories):
   \   g:dir . '/python_paths/with_virtualenv/env/bin/flake8'
   \   . ' --stdin-display-name %s -',
   \ ale_linters#python#flake8#GetCommand(bufnr(''), ['3.0.0'])
+
+" Some users currently run flake8 this way, so we should support it.
+Execute(Using `python -m flake8` should be supported for running flake8):
+  silent execute 'file ' . fnameescape(g:dir . '/python_paths/with_virtualenv/subdir/foo/bar.py')
+
+  let g:ale_python_flake8_executable = 'python'
+  let g:ale_python_flake8_options = '-m flake8 --some-option'
+
+  AssertEqual
+  \ 'python',
+  \ ale_linters#python#flake8#GetExecutable(bufnr(''))
+  AssertEqual
+  \ 'python -m flake8 --version',
+  \ ale_linters#python#flake8#VersionCheck(bufnr(''))
+  AssertEqual
+  \ 'python -m flake8 --some-option -',
+  \ ale_linters#python#flake8#GetCommand(bufnr(''), ['2.9.9'])
+
+  call ale_linters#python#flake8#ClearVersionCache()
+
+  " Leading spaces shouldn't matter
+  let g:ale_python_flake8_options = '  -m flake8 --some-option'
+
+  AssertEqual
+  \ 'python',
+  \ ale_linters#python#flake8#GetExecutable(bufnr(''))
+  AssertEqual
+  \ 'python -m flake8 --version',
+  \ ale_linters#python#flake8#VersionCheck(bufnr(''))
+  AssertEqual
+  \ 'python   -m flake8 --some-option -',
+  \ ale_linters#python#flake8#GetCommand(bufnr(''), ['2.9.9'])