#371 Allow buffer variables to be set based on patterns

autoload/ale/pattern_options.vim

@@ -0,0 +1,18 @@
+" Author: w0rp <devw0rp@gmail.com>
+" Description: Set options in files based on regex patterns.
+
+function! ale#pattern_options#SetOptions() abort
+    let l:filename = expand('%:p')
+    let l:options = {}
+
+    for l:pattern in keys(g:ale_pattern_options)
+        if match(l:filename, l:pattern) >= 0
+            let l:options = g:ale_pattern_options[l:pattern]
+            break
+        endif
+    endfor
+
+    for l:key in keys(l:options)
+        let b:[l:key] = l:options[l:key]
+    endfor
+endfunction

doc/ale.txt

@@ -517,6 +517,41 @@ g:ale_open_list                                               *g:ale_open_list*
   to `1`, in which case the window will be kept open until closed manually.
 
 
+g:ale_pattern_options                                   *g:ale_pattern_options*
+
+  Type: |Dictionary|
+  Default: `{}`
+
+  This option maps regular expression patterns to |Dictionary| values for
+  buffer variables. This option can be set to automatically configure
+  different settings for different files. For example: >
+
+  let g:ale_pattern_options = {
+  \   '\.foo\.js$': {
+  \       'ale_linters: {'javascript': ['eslint']},
+  \   },
+  \}
+<
+  The above example will match any filename ending in `.foo.js`, and use
+  only `eslint` for checking those files by setting `b:ale_linters`.
+
+  Filenames are matched with |match()|, and patterns depend on the |magic|
+  setting, unless prefixed with the special escape sequences like `'\v'`, etc.
+
+  The patterns can match any part of a filename. The absolute path of the
+  filename will be used for matching, taken from `expand('%:p')`.
+
+
+g:ale_pattern_options_enabled                   *g:ale_pattern_options_enabled*
+
+  Type: |Number|
+  Default: `!empty(g:ale_pattern_options)`
+
+  This option can be used for turning the behaviour of setting
+  |g:ale_pattern_options| on or off. By default, setting a single key
+  for |g:ale_pattern_options| will turn this option on.
+
+
 g:ale_set_highlights                                     *g:ale_set_highlights*
 
   Type: |Number|

plugin/ale.vim

@@ -161,10 +161,23 @@ let g:ale_history_enabled = get(g:, 'ale_history_enabled', 1)
 " A flag for storing the full output of commands in the history.
 let g:ale_history_log_output = get(g:, 'ale_history_log_output', 0)
 
+" A dictionary mapping regular expression patterns to arbitrary buffer
+" variables to be set. Useful for configuration ALE based on filename
+" patterns.
+call ale#Set('pattern_options', {})
+call ale#Set('pattern_options_enabled', !empty(g:ale_pattern_options))
+
 function! ALEInitAuGroups() abort
     " This value used to be a Boolean as a Number, and is now a String.
     let l:text_changed = '' . g:ale_lint_on_text_changed
 
+    augroup ALEPatternOptionsGroup
+        autocmd!
+        if g:ale_enabled && g:ale_pattern_options_enabled
+            autocmd BufEnter,BufRead * call ale#pattern_options#SetOptions()
+        endif
+    augroup END
+
     augroup ALERunOnTextChangedGroup
         autocmd!
         if g:ale_enabled
@@ -226,6 +239,7 @@ function! ALEInitAuGroups() abort
     augroup END
 
     if !g:ale_enabled
+        augroup! ALEPatternOptionsGroup
         augroup! ALERunOnTextChangedGroup
         augroup! ALERunOnEnterGroup
         augroup! ALERunOnSaveGroup
@@ -238,6 +252,11 @@ function! s:ALEToggle() abort
     let g:ale_enabled = !get(g:, 'ale_enabled')
 
     if g:ale_enabled
+        " Set pattern options again, if enabled.
+        if g:ale_pattern_options_enabled
+            call ale#pattern_options#SetOptions()
+        endif
+
         " Lint immediately, including running linters against the file.
         call ale#Queue(0, 'lint_file')
     else

test/test_pattern_options.vader

@@ -0,0 +1,28 @@
+Before:
+  Save g:ale_pattern_options, g:ale_pattern_options_enabled
+
+After:
+  Restore
+
+  unlet! b:ale_enabled
+  unlet! b:some_option
+
+Execute(Buffer variables should be set when filename patterns match):
+  let g:ale_pattern_options = {'baz.*\.js': {
+  \ 'ale_enabled': 1,
+  \ 'some_option': 347,
+  \}}
+
+  silent! file foobar.js
+
+  call ale#pattern_options#SetOptions()
+
+  Assert !exists('b:ale_enabled')
+  Assert !exists('b:some_option')
+
+  silent! file bazboz.js
+
+  call ale#pattern_options#SetOptions()
+
+  AssertEqual 1, b:ale_enabled
+  AssertEqual 347, b:some_option