Add Black support for Python formatting

Author: brentyi

README.md

@@ -23,7 +23,7 @@ helpfiles in the `doc/` directory. The helpfiles are also available via
 * JavaScript (clang-format or [prettier](https://prettier.io))
 * JSON (js-beautify)
 * Proto (clang-format)
-* Python (Autopep8 or YAPF)
+* Python (Autopep8, YAPF, or Black)
 * Rust ([rustfmt](https://github.com/rust-lang/rustfmt))
 * TypeScript (clang-format)
 * Shell (shfmt)

autoload/codefmt.vim

@@ -33,7 +33,7 @@
 "   * fish: fish_indent
 "   * gn: gn
 "   * go: gofmt
-"   * python: autopep8, yapf
+"   * python: autopep8, yapf, black
 
 
 let s:plugin = maktaba#plugin#Get('codefmt')

autoload/codefmt/black.vim

@@ -0,0 +1,51 @@
+" Copyright 2020 Google Inc. All rights reserved.
+"
+" Licensed under the Apache License, Version 2.0 (the "License");
+" you may not use this file except in compliance with the License.
+" You may obtain a copy of the License at
+"
+"     http://www.apache.org/licenses/LICENSE-2.0
+"
+" Unless required by applicable law or agreed to in writing, software
+" distributed under the License is distributed on an "AS IS" BASIS,
+" WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+" See the License for the specific language governing permissions and
+" limitations under the License.
+
+
+let s:plugin = maktaba#plugin#Get('codefmt')
+
+
+""
+" @private
+" Formatter: black
+function! codefmt#black#GetFormatter() abort
+  let l:formatter = {
+      \ 'name': 'black',
+      \ 'setup_instructions': 'Install black ' .
+          \ '(https://pypi.python.org/pypi/black/).'}
+
+  function l:formatter.IsAvailable() abort
+    return executable(s:plugin.Flag('black_executable'))
+  endfunction
+
+  function l:formatter.AppliesToBuffer() abort
+    return &filetype is# 'python'
+  endfunction
+
+  ""
+  " Reformat the current buffer with black or the binary named in
+  " @flag(black_executable)
+  "
+  " We implement Format(), and not FormatRange{,s}(), because black doesn't
+  " provide a hook for formatting a range
+  function l:formatter.Format() abort
+    let l:executable = s:plugin.Flag('black_executable')
+
+    call codefmt#formatterhelpers#Format([
+        \ l:executable,
+        \ '-'])
+  endfunction
+
+  return l:formatter
+endfunction

doc/codefmt.txt

@@ -57,6 +57,10 @@ Default: 'js-beautify' `
 The path to the yapf executable.
 Default: 'yapf' `
 
+                                                     *codefmt:black_executable*
+The path to the black executable.
+Default: 'black' `
+
                                                        *codefmt:gn_executable*
 The path to the gn executable.
 Default: 'gn' `
@@ -162,7 +166,7 @@ The current list of defaults by filetype is:
   * fish: fish_indent
   * gn: gn
   * go: gofmt
-  * python: autopep8, yapf
+  * python: autopep8, yapf, black
 
 ==============================================================================
 DICTIONARIES                                                   *codefmt-dicts*

instant/flags.vim

@@ -83,6 +83,10 @@ call s:plugin.Flag('js_beautify_executable', 'js-beautify')
 " The path to the yapf executable.
 call s:plugin.Flag('yapf_executable', 'yapf')
 
+""
+" The path to the black executable.
+call s:plugin.Flag('black_executable', 'black')
+
 ""
 " The path to the gn executable.
 call s:plugin.Flag('gn_executable', 'gn')

plugin/register.vim

@@ -30,6 +30,7 @@ call s:registry.AddExtension(codefmt#clangformat#GetFormatter())
 call s:registry.AddExtension(codefmt#gofmt#GetFormatter())
 call s:registry.AddExtension(codefmt#dartfmt#GetFormatter())
 call s:registry.AddExtension(codefmt#yapf#GetFormatter())
+call s:registry.AddExtension(codefmt#black#GetFormatter())
 call s:registry.AddExtension(codefmt#autopep8#GetFormatter())
 call s:registry.AddExtension(codefmt#gn#GetFormatter())
 call s:registry.AddExtension(codefmt#buildifier#GetFormatter())