Added support for Python black fixer (#1451)

8 files changed, 100 insertions, 2 deletions

diff --git a/README.md b/README.md
index 26699126..5f06d945 100644
--- a/README.md
+++ b/README.md
@@ -139,7 +139,7 @@ formatting.
 | proto | [protoc-gen-lint](https://github.com/ckaznocha/protoc-gen-lint) |
 | Pug | [pug-lint](https://github.com/pugjs/pug-lint) |
 | Puppet | [puppet](https://puppet.com), [puppet-lint](https://puppet-lint.com) |
-| Python | [autopep8](https://github.com/hhatto/autopep8), [flake8](http://flake8.pycqa.org/en/latest/), [isort](https://github.com/timothycrosley/isort), [mypy](http://mypy-lang.org/), [prospector](http://github.com/landscapeio/prospector), [pycodestyle](https://github.com/PyCQA/pycodestyle), [pyls](https://github.com/palantir/python-language-server), [pylint](https://www.pylint.org/) !!, [yapf](https://github.com/google/yapf) |
+| Python | [autopep8](https://github.com/hhatto/autopep8), [black](https://github.com/ambv/black), [flake8](http://flake8.pycqa.org/en/latest/), [isort](https://github.com/timothycrosley/isort), [mypy](http://mypy-lang.org/), [prospector](http://github.com/landscapeio/prospector), [pycodestyle](https://github.com/PyCQA/pycodestyle), [pyls](https://github.com/palantir/python-language-server), [pylint](https://www.pylint.org/) !!, [yapf](https://github.com/google/yapf) |
 | QML | [qmlfmt](https://github.com/jesperhh/qmlfmt), [qmllint](https://github.com/qt/qtdeclarative/tree/5.11/tools/qmllint) |
 | R | [lintr](https://github.com/jimhester/lintr) |
 | ReasonML | [merlin](https://github.com/the-lambda-church/merlin) see `:help ale-reasonml-ols` for configuration instructions, [ols](https://github.com/freebroccolo/ocaml-language-server), [refmt](https://github.com/reasonml/reason-cli) |
diff --git a/autoload/ale/fix/registry.vim b/autoload/ale/fix/registry.vim
index 4c0703a5..86a10908 100644
--- a/autoload/ale/fix/registry.vim
+++ b/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'],
diff --git a/autoload/ale/fixers/black.vim b/autoload/ale/fixers/black.vim
new file mode 100644
index 00000000..6f6d56f3
--- /dev/null
+++ b/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
diff --git a/doc/ale-python.txt b/doc/ale-python.txt
index 4d55e751..dc7c8bba 100644
--- a/doc/ale-python.txt
+++ b/doc/ale-python.txt
@@ -30,6 +30,33 @@ g:ale_python_autopep8_use_global             *g:ale_python_autopep8_use_global*
 
 
 ===============================================================================
+black                                                        *ale-python-black*
+
+g:ale_python_black_executable                   *g:ale_python_black_executable*
+                                                *b:ale_python_black_executable*
+  Type: |String|
+  Default: `'black'`
+
+  See |ale-integrations-local-executables|
+
+autopep8
+g:ale_python_black_options                         *g:ale_python_black_options*
+                                                   *b:ale_python_black_options*
+  Type: |String|
+  Default: `''`
+
+  This variable can be set to pass extra options to black.
+
+
+g:ale_python_black_use_global                   *g:ale_python_black_use_global*
+                                                *b:ale_python_black_use_global*
+  Type: |Number|
+  Default: `0`
+
+  See |ale-integrations-local-executables|
+
+
+===============================================================================
 flake8                                                      *ale-python-flake8*
 
 g:ale_python_flake8_executable                 *g:ale_python_flake8_executable*
diff --git a/doc/ale.txt b/doc/ale.txt
index 4ba8e649..2e5c5e47 100644
--- a/doc/ale.txt
+++ b/doc/ale.txt
@@ -179,6 +179,7 @@ CONTENTS                                                         *ale-contents*
       puppetlint..........................|ale-puppet-puppetlint|
     python................................|ale-python-options|
       autopep8............................|ale-python-autopep8|
+      black...............................|ale-python-black|
       flake8..............................|ale-python-flake8|
       isort...............................|ale-python-isort|
       mypy................................|ale-python-mypy|
@@ -369,7 +370,7 @@ Notes:
 * proto: `protoc-gen-lint`
 * Pug: `pug-lint`
 * Puppet: `puppet`, `puppet-lint`
-* Python: `autopep8`, `flake8`, `isort`, `mypy`, `prospector`, `pycodestyle`, `pyls`, `pylint`!!, `yapf`
+* Python: `autopep8`, `black`, `flake8`, `isort`, `mypy`, `prospector`, `pycodestyle`, `pyls`, `pylint`!!, `yapf`
 * QML: `qmlfmt`, `qmllint`
 * R: `lintr`
 * ReasonML: `merlin`, `ols`, `refmt`
diff --git a/test/command_callback/python_paths/with_virtualenv/env/Scripts/black.exe b/test/command_callback/python_paths/with_virtualenv/env/Scripts/black.exe
new file mode 100755
index 00000000..e69de29b
--- /dev/null
+++ b/test/command_callback/python_paths/with_virtualenv/env/Scripts/black.exe
diff --git a/test/command_callback/python_paths/with_virtualenv/env/bin/black b/test/command_callback/python_paths/with_virtualenv/env/bin/black
new file mode 100755
index 00000000..e69de29b
--- /dev/null
+++ b/test/command_callback/python_paths/with_virtualenv/env/bin/black
diff --git a/test/fixers/test_black_fixer_callback.vader b/test/fixers/test_black_fixer_callback.vader
new file mode 100644
index 00000000..365b0fa6
--- /dev/null
+++ b/test/fixers/test_black_fixer_callback.vader
@@ -0,0 +1,39 @@
+Before:
+  Save g:ale_python_black_executable
+  Save g:ale_python_black_options
+
+  " Use an invalid global executable, so we don't match it.
+  let g:ale_python_black_executable = 'xxxinvalid'
+  let g:ale_python_black_options = ''
+
+  call ale#test#SetDirectory('/testplugin/test/fixers')
+  silent cd ..
+  silent cd command_callback
+  let g:dir = getcwd()
+
+  let b:bin_dir = has('win32') ? 'Scripts' : 'bin'
+
+After:
+  Restore
+
+  unlet! b:bin_dir
+
+  call ale#test#RestoreDirectory()
+
+Execute(The black callback should return the correct default values):
+  AssertEqual
+  \ 0,
+  \ ale#fixers#black#Fix(bufnr(''))
+
+  silent execute 'file ' . fnameescape(g:dir . '/python_paths/with_virtualenv/subdir/foo/bar.py')
+  AssertEqual
+  \ {'command': ale#Escape(ale#path#Simplify(g:dir . '/python_paths/with_virtualenv/env/' . b:bin_dir . '/black')) . ' -'},
+  \ ale#fixers#black#Fix(bufnr(''))
+
+Execute(The black callback should include options):
+  let g:ale_python_black_options = '--some-option'
+
+  silent execute 'file ' . fnameescape(g:dir . '/python_paths/with_virtualenv/subdir/foo/bar.py')
+  AssertEqual
+  \ {'command': ale#Escape(ale#path#Simplify(g:dir . '/python_paths/with_virtualenv/env/' . b:bin_dir . '/black')) . ' --some-option -' },
+  \ ale#fixers#black#Fix(bufnr(''))