Add PyLS linter (#1097)

* Support PyLS (python language server)
* Replace pyls#GetProjectRoot and add more config types to ale#python#FindProjectRoot

README.md

@@ -126,7 +126,7 @@ formatting.
 | Pod | [proselint](http://proselint.com/), [write-good](https://github.com/btford/write-good) |
 | 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/), [pycodestyle](https://github.com/PyCQA/pycodestyle), [pylint](https://www.pylint.org/) !!, [yapf](https://github.com/google/yapf) |
+| 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/), [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) |
 | R | [lintr](https://github.com/jimhester/lintr) |
 | ReasonML | [merlin](https://github.com/the-lambda-church/merlin) see `:help ale-integration-reason-merlin` for configuration instructions, [refmt](https://github.com/reasonml/reason-cli) |
 | reStructuredText | [proselint](http://proselint.com/), [write-good](https://github.com/btford/write-good) |

ale_linters/python/pyls.vim

@@ -0,0 +1,21 @@
+" Author: aurieh <me@aurieh.me>
+" Description: A language server for Python
+
+call ale#Set('python_pyls_executable', 'pyls')
+
+function! ale_linters#python#pyls#GetExecutable(buffer) abort
+    return ale#Var(a:buffer, 'python_pyls_executable')
+endfunction
+
+function! ale_linters#python#pyls#GetLanguage(buffer) abort
+    return 'python'
+endfunction
+
+call ale#linter#Define('python', {
+\   'name': 'pyls',
+\   'lsp': 'stdio',
+\   'executable_callback': 'ale_linters#python#pyls#GetExecutable',
+\   'command_callback': 'ale_linters#python#pyls#GetExecutable',
+\   'language_callback': 'ale_linters#python#pyls#GetLanguage',
+\   'project_root_callback': 'ale#python#FindProjectRoot',
+\})

autoload/ale/python.vim

@@ -18,6 +18,8 @@ function! ale#python#FindProjectRootIni(buffer) abort
         \|| filereadable(l:path . '/setup.cfg')
         \|| filereadable(l:path . '/pytest.ini')
         \|| filereadable(l:path . '/tox.ini')
+        \|| filereadable(l:path . '/pycodestyle.cfg')
+        \|| filereadable(l:path . '/flake8.cfg')
             return l:path
         endif
     endfor

doc/ale-python.txt

@@ -189,6 +189,15 @@ g:ale_python_pylint_use_global                 *g:ale_python_pylint_use_global*
 
   See |ale-integrations-local-executables|
 
+===============================================================================
+pyls                                                          *ale-python-pyls*
+
+g:ale_python_pyls_executable                     *g:ale_python_pyls_executable*
+                                                 *b:ale_python_pyls_executable*
+  Type: |String|
+  Default: `pyls`
+
+  See |ale-integrations-local-executables|
 
 ===============================================================================
 yapf                                                          *ale-python-yapf*

doc/ale.txt

@@ -145,6 +145,7 @@ CONTENTS                                                         *ale-contents*
       mypy................................|ale-python-mypy|
       pycodestyle.........................|ale-python-pycodestyle|
       pylint..............................|ale-python-pylint|
+      pyls................................|ale-python-pyls|
       yapf................................|ale-python-yapf|
     r.....................................|ale-r-options|
       lintr...............................|ale-r-lintr|
@@ -309,7 +310,7 @@ Notes:
 * Pod: `proselint`, `write-good`
 * Pug: `pug-lint`
 * Puppet: `puppet`, `puppet-lint`
-* Python: `autopep8`, `flake8`, `isort`, `mypy`, `pycodestyle`, `pylint`!!, `yapf`
+* Python: `autopep8`, `flake8`, `isort`, `mypy`, `pycodestyle`, `pyls`, `pylint`!!, `yapf`
 * R: `lintr`
 * ReasonML: `merlin`, `refmt`
 * reStructuredText: `proselint`, `write-good`