Add a unimport linter for Python files (#4058)

Unimport (https://github.com/hakancelik96/unimport/) is a linter,
formatter for finding and removing unused import statements.

This introduces linting support, although fixer support could come
later.

1 files changed, 75 insertions, 0 deletions

diff --git a/ale_linters/python/unimport.vim b/ale_linters/python/unimport.vim
new file mode 100644
index 00000000..71fd80f0
--- /dev/null
+++ b/ale_linters/python/unimport.vim
@@ -0,0 +1,75 @@
+" Author: Author: Jon Parise <jon@indelible.org>
+
+call ale#Set('python_unimport_executable', 'unimport')
+call ale#Set('python_unimport_options', '')
+call ale#Set('python_unimport_use_global', get(g:, 'ale_use_global_executables', 0))
+call ale#Set('python_unimport_auto_pipenv', 0)
+call ale#Set('python_unimport_auto_poetry', 0)
+
+function! ale_linters#python#unimport#GetExecutable(buffer) abort
+    if (ale#Var(a:buffer, 'python_auto_pipenv') || ale#Var(a:buffer, 'python_unimport_auto_pipenv'))
+    \ && ale#python#PipenvPresent(a:buffer)
+        return 'pipenv'
+    endif
+
+    if (ale#Var(a:buffer, 'python_auto_poetry') || ale#Var(a:buffer, 'python_unimport_auto_poetry'))
+    \ && ale#python#PoetryPresent(a:buffer)
+        return 'poetry'
+    endif
+
+    return ale#python#FindExecutable(a:buffer, 'python_unimport', ['unimport'])
+endfunction
+
+function! ale_linters#python#unimport#GetCommand(buffer) abort
+    let l:executable = ale_linters#python#unimport#GetExecutable(a:buffer)
+    let l:exec_args = l:executable =~? 'pipenv\|poetry$'
+    \   ? ' run unimport'
+    \   : ''
+
+    return '%e' . l:exec_args
+    \   . ale#Pad(ale#Var(a:buffer, 'python_unimport_options'))
+    \   . ' --check'
+    \   . ' %t'
+endfunction
+
+
+function! ale_linters#python#unimport#GetCwd(buffer) abort
+    let l:project_root = ale#python#FindProjectRoot(a:buffer)
+
+    return !empty(l:project_root)
+    \   ? l:project_root
+    \   : expand('#' . a:buffer . ':p:h')
+endfunction
+
+
+function! ale_linters#python#unimport#Handle(buffer, lines) abort
+    let l:output = ale#python#HandleTraceback(a:lines, 10)
+
+    if !empty(l:output)
+        return l:output
+    endif
+
+    " Matches lines like:
+    "
+    " urllib.parse at path/to/file.py:9
+    let l:pattern = '\v(.+) at [^:]+:(\d+)$'
+
+    for l:match in ale#util#GetMatches(a:lines, l:pattern)
+        call add(l:output, {
+        \   'lnum': l:match[2] + 0,
+        \   'type': 'W',
+        \   'text': 'unused: ' . l:match[1],
+        \})
+    endfor
+
+    return l:output
+endfunction
+
+
+call ale#linter#Define('python', {
+\   'name': 'unimport',
+\   'executable': function('ale_linters#python#unimport#GetExecutable'),
+\   'cwd': function('ale_linters#python#unimport#GetCwd'),
+\   'command': function('ale_linters#python#unimport#GetCommand'),
+\   'callback': 'ale_linters#python#unimport#Handle',
+\})