yamlfmt (#4587)

* Added the fixer, wrote tests and tested it

autoload/ale/fix/registry.vim

@@ -179,7 +179,12 @@ let s:default_registry = {
 \   'yamlfix': {
 \       'function': 'ale#fixers#yamlfix#Fix',
 \       'suggested_filetypes': ['yaml'],
-\       'description': 'Fix yaml files with yamlfix.',
+\       'description': 'Fix YAML files with yamlfix.',
+\   },
+\   'yamlfmt': {
+\       'function': 'ale#fixers#yamlfmt#Fix',
+\       'suggested_filetypes': ['yaml'],
+\       'description': 'Format YAML files with yamlfmt.',
 \   },
 \   'yapf': {
 \       'function': 'ale#fixers#yapf#Fix',

autoload/ale/fixers/yamlfmt.vim

@@ -0,0 +1,20 @@
+" Author: https://github.com/Spixmaster
+" Description: Format YAML files with yamlfmt.
+
+call ale#Set('yaml_yamlfmt_executable', 'yamlfmt')
+call ale#Set('yaml_yamlfmt_use_global', get(g:, 'ale_use_global_executables', 0))
+call ale#Set('yaml_yamlfmt_options', '')
+
+function! ale#fixers#yamlfmt#Fix(buffer) abort
+    let l:executable = ale#python#FindExecutable(
+    \   a:buffer,
+    \   'yaml_yamlfmt',
+    \   ['yamlfmt']
+    \)
+
+    let l:options = ale#Var(a:buffer, 'yaml_yamlfmt_options')
+
+    return {
+    \   'command': ale#Escape(l:executable) . ' ' . l:options . ' -in',
+    \}
+endfunction