add rustfmt fixer

autoload/ale/fix/registry.vim

@@ -107,6 +107,11 @@ let s:default_registry = {
 \       'suggested_filetypes': ['typescript'],
 \       'description': 'Fix typescript files with tslint --fix.',
 \   },
+\   'rustfmt': {
+\       'function': 'ale#fixers#rustfmt#Fix',
+\       'suggested_filetypes': ['rust'],
+\       'description': 'Fix Rust files with Rustfmt.',
+\   },
 \}
 
 " Reset the function registry to the default entries.

autoload/ale/fixers/rustfmt.vim

@@ -0,0 +1,17 @@
+" Author: Kelly Fox <kelly@bumfuddled.com>
+" Description: Integration of rustfmt with ALE.
+
+call ale#Set('rust_rustfmt_executable', 'rustfmt')
+call ale#Set('rust_rustfmt_options', '')
+
+function! ale#fixers#rustfmt#Fix(buffer) abort
+    let l:executable = ale#Var(a:buffer, 'rust_rustfmt_executable')
+    let l:options = ale#Var(a:buffer, 'rust_rustfmt_options')
+
+    return {
+    \   'command': ale#Escape(l:executable)
+    \       . (empty(l:options) ? '' : ' ' . l:options)
+    \       . ' %t',
+    \   'read_temporary_file': 1,
+    \}
+endfunction