Add support for prettier configuration file. (#886)

* Add support for prettier configuration file.

As of version 1.6.0, prettier allows passing a `--config` argument with
a path to a configuration file.

* Add test prettier configuration file.

* Add option to use local prettier configuration.

* Add description for new prettier option.

* Also check if the config is present before using it.

autoload/ale/fixers/prettier.vim

@@ -4,8 +4,27 @@
 
 call ale#Set('javascript_prettier_executable', 'prettier')
 call ale#Set('javascript_prettier_use_global', 0)
+call ale#Set('javascript_prettier_use_local_config', 0)
 call ale#Set('javascript_prettier_options', '')
 
+function! s:FindConfig(buffer) abort
+    for l:filename in [
+    \   '.prettierrc',
+    \   'prettier.config.js',
+    \   'package.json',
+    \ ]
+
+        let l:config = ale#path#FindNearestFile(a:buffer, l:filename)
+
+        if !empty(l:config)
+            return l:config
+        endif
+    endfor
+
+    return ''
+endfunction
+
+
 function! ale#fixers#prettier#GetExecutable(buffer) abort
     return ale#node#FindExecutable(a:buffer, 'javascript_prettier', [
     \   'node_modules/.bin/prettier_d',
@@ -16,11 +35,15 @@ endfunction
 
 function! ale#fixers#prettier#Fix(buffer) abort
     let l:options = ale#Var(a:buffer, 'javascript_prettier_options')
+    let l:config = s:FindConfig(a:buffer)
+    let l:use_config = ale#Var(a:buffer, 'javascript_prettier_use_local_config')
+                \ && !empty(l:config)
 
     return {
     \   'command': ale#Escape(ale#fixers#prettier#GetExecutable(a:buffer))
     \       . ' %t'
-    \       . ' ' . l:options
+    \       . (!empty(l:options) ? ' ' . l:options : '')
+    \       . (l:use_config ? ' --config ' . ale#Escape(l:config) : '')
     \       . ' --write',
     \   'read_temporary_file': 1,
     \}

doc/ale-javascript.txt

@@ -86,6 +86,12 @@ g:ale_javascript_prettier_use_global     *g:ale_javascript_prettier_use_global*
 
   See |ale-integrations-local-executables|
 
+g:ale_javascript_prettier_use_local_config     *g:ale_javascript_prettier_use_local_config*
+                                               *b:ale_javascript_prettier_use_local_config*
+  Type: |Number|
+  Default: `0`
+
+  This variable can be set to use the local prettier configuration file.
 
 ===============================================================================
 prettier-eslint                                *ale-javascript-prettier-eslint*

test/fixers/test_prettier_fixer_callback.vader

@@ -0,0 +1,58 @@
+Before:
+  call ale#test#SetDirectory('/testplugin/test/fixers')
+  Save g:ale_javascript_prettier_executable
+  Save g:ale_javascript_prettier_options
+
+  " Use an invalid global executable, so we don't match it.
+  let g:ale_javascript_prettier_executable = 'xxxinvalid'
+  let g:ale_javascript_prettier_options = ''
+
+  call ale#test#SetDirectory('/testplugin/test/fixers')
+  silent cd ..
+  silent cd command_callback
+  let g:dir = getcwd()
+
+After:
+  let g:ale_has_override = {}
+  call ale#test#RestoreDirectory()
+
+Execute(The prettier callback should return the correct default values):
+  call ale#test#SetFilename('../prettier-test-files/testfile.js')
+
+  AssertEqual
+  \ {
+  \   'read_temporary_file': 1,
+  \   'command': ale#Escape(g:ale_javascript_prettier_executable)
+  \     . ' %t'
+  \     . ' --write',
+  \ },
+  \ ale#fixers#prettier#Fix(bufnr(''))
+
+Execute(The prettier callback should include configuration files when the option is set):
+  let g:ale_javascript_prettier_use_local_config = 1
+  call ale#test#SetFilename('../prettier-test-files/with_config/testfile.js')
+
+  AssertEqual
+  \ {
+  \   'read_temporary_file': 1,
+  \   'command': ale#Escape(g:ale_javascript_prettier_executable)
+  \     . ' %t'
+  \     . ' --config ' . ale#Escape(simplify(g:dir .  '/../prettier-test-files/with_config/.prettierrc'))
+  \     . ' --write',
+  \ },
+  \ ale#fixers#prettier#Fix(bufnr(''))
+
+Execute(The prettier callback should include custom prettier options):
+  let g:ale_javascript_prettier_options = '--no-semi'
+  call ale#test#SetFilename('../prettier-test-files/with_config/testfile.js')
+
+  AssertEqual
+  \ {
+  \   'read_temporary_file': 1,
+  \   'command': ale#Escape(g:ale_javascript_prettier_executable)
+  \     . ' %t'
+  \     . ' --no-semi'
+  \     . ' --config ' . ale#Escape(simplify(g:dir .  '/../prettier-test-files/with_config/.prettierrc'))
+  \     . ' --write',
+  \ },
+  \ ale#fixers#prettier#Fix(bufnr(''))