Added support for Python black fixer (#1451)

autoload/ale/fix/registry.vim

@@ -17,6 +17,11 @@ let s:default_registry = {
 \       'suggested_filetypes': ['python'],
 \       'description': 'Fix PEP8 issues with autopep8.',
 \   },
+\   'black': {
+\       'function': 'ale#fixers#black#Fix',
+\       'suggested_filetypes': ['python'],
+\       'description': 'Fix PEP8 issues with black.',
+\   },
 \   'prettier_standard': {
 \       'function': 'ale#fixers#prettier_standard#Fix',
 \       'suggested_filetypes': ['javascript'],

autoload/ale/fixers/black.vim

@@ -0,0 +1,26 @@
+" Author: w0rp <devw0rp@gmail.com>
+" Description: Fixing Python files with black.
+"
+call ale#Set('python_black_executable', 'black')
+call ale#Set('python_black_use_global', 0)
+call ale#Set('python_black_options', '')
+
+function! ale#fixers#black#Fix(buffer) abort
+    let l:executable = ale#python#FindExecutable(
+    \   a:buffer,
+    \   'python_black',
+    \   ['black'],
+    \)
+
+    if !executable(l:executable)
+        return 0
+    endif
+
+    let l:options = ale#Var(a:buffer, 'python_black_options')
+
+    return {
+    \   'command': ale#Escape(l:executable)
+    \       . (!empty(l:options) ? ' ' . l:options : '')
+    \       . ' -',
+    \}
+endfunction