feature: implement local ESLint support

Support to use the project local eslint installation to be used to
reformat javascript source with the eslint --fix command

README.md

@@ -158,6 +158,16 @@ Here is a list of formatprograms that are supported by default, and thus will be
   It can be installed by running `npm install -g standard` (`nodejs` is required). No more configuration needed.
   More information about the style guide can be found here: http://standardjs.com/.
 
+* `ESlint (local)` for __Javascript__. http://eslint.org/
+  It can be installed by running `npm install eslint`. The linter is then installed locally at ```node_modules/.bin/eslint```
+  When opening a javascript file (```vim autocmd FileType javscript```) vim will walk up from the current file to search for such local installation and a
+  ESLint configuration file (either .eslintrc or eslintrc.json). When both are   found eslint will 	be configured as first javascript formatter.
+  This linter can be disabled using global setting
+  ```vim
+  let g:formatters_javascript_eslint_local = 0
+  ```
+  Currently only working on *nix like OS (Linux, MacOS etc.) requires OS to provide sh like shell syntax
+
 * `xo` for __Javascript__.
   It can be installed by running `npm install -g xo` (`nodejs` is required).
   Here is the link to the repository: https://github.com/sindresorhus/xo.

plugin/defaults.vim

@@ -160,6 +160,82 @@ if !exists('g:formatdef_xo_javascript')
     let g:formatdef_xo_javascript = '"xo --fix --stdin"'
 endif
 
+" Setup ESLint local. Setup is done for each file in an autocmd to make sure
+" the most local instance of ESLint and corresponding config is used.
+" No windows support at the moment.
+if !exists('g:formatdef_eslint_local') && !has('win32')
+	" set disable flag when not defined already
+	let g:formatters_javascript_eslint_local = exists('g:formatters_javascript_eslint_local') ? g:formatters_javascript_eslint_local : 1
+	" find file upwards the filesystem
+	function! s:find_upward(path, filename)  
+		let l:current_folder = fnamemodify(a:path, ':p:h')
+		if l:current_folder == "/"
+			return
+		endif
+		let l:prog = l:current_folder.a:filename
+		if filereadable(l:prog)
+			return l:prog
+		elseif l:current_folder == "/"
+			return
+		else
+			return s:find_upward(fnamemodify(l:current_folder, ':h'), a:filename)
+		endif
+	endfunction
+
+	" add 'eslint_local' as first javscript formatter
+	function s:register_eslint_local() 
+		let l:index = index(g:formatters_javascript, 'eslint_local')
+		if l:index == -1
+			call insert(g:formatters_javascript, 'eslint_local', 0)
+		endif
+	endfunction
+
+	" remmove 'eslint_local' from javscript formatters
+	function s:unregister_eslint_local() 
+		let l:index = index(g:formatters_javascript, 'eslint_local')
+		if l:index != -1
+			call remove(g:formatters_javascript, l:index)
+		endif
+	endfunction
+
+	function! s:setup_eslint_local_cmd(path)
+		let verbose = &verbose || g:autoformat_verbosemode == 1
+		if g:formatters_javascript_eslint_local == 0
+			echomsg 'Disable ESLint local'
+			call s:unregister_eslint_local()
+			return
+		endif
+		" find formatter & config file
+		let l:prog = s:find_upward(a:path, '/node_modules/.bin/eslint')
+		let l:cfg = s:find_upward(a:path, '/.eslintrc.json')
+		if empty(l:cfg)
+			let l:cfg = s:find_upward(a:path, '/.eslintrc')
+		endif
+		if (empty(l:cfg) || empty(l:prog))
+			if verbose
+				echomsg 'No local ESLint program and/or config found'
+			endif
+			call s:unregister_eslint_local();
+			return 
+		endif
+
+		" This formatter uses a temporary file as ESLint has not option to only
+		" print the formatted source to stdout. It will allways modify the file 
+		" in place.
+		if !exists('l:eslint_js_tmp_file')
+			let l:eslint_js_tmp_file = fnameescape(tempname().".js")
+		endif
+		let g:formatdef_eslint_local = 
+					\ '"rm -f '.l:eslint_js_tmp_file.';
+					\ cat '.expand('%').' > '.l:eslint_js_tmp_file.'; '
+					\ .l:prog.' -c '.l:cfg.' --fix '.l:eslint_js_tmp_file.' 1> /dev/null; exit_code=$?
+					\ cat '.l:eslint_js_tmp_file.'; rm -f '.l:eslint_js_tmp_file.'; exit $exit_code"'
+		call s:register_eslint_local()	
+	endfunction
+	" register hook to setup lint command correctly for the current file
+	autocmd FileType javascript call s:setup_eslint_local_cmd(expand('<afile>'))
+endif
+
 if !exists('g:formatters_javascript')
     let g:formatters_javascript = [
                 \ 'jsbeautify_javascript',