fixers/xo: support stdin relative to the fixed file

autoload/ale/fixers/xo.vim

@@ -14,10 +14,35 @@ function! ale#fixers#xo#Fix(buffer) abort
     let l:executable = ale#handlers#xo#GetExecutable(a:buffer, l:type)
     let l:options = ale#handlers#xo#GetOptions(a:buffer, l:type)
 
+    return ale#semver#RunWithVersionCheck(
+    \   a:buffer,
+    \   l:executable,
+    \   '%e --version',
+    \   {b, v -> ale#fixers#xo#ApplyFixForVersion(b, v, l:executable, l:options)}
+    \)
+endfunction
+
+function! ale#fixers#xo#ApplyFixForVersion(buffer, version, executable, options) abort
+    let l:executable = ale#node#Executable(a:buffer, a:executable)
+    let l:options = ale#Pad(a:options)
+
+    " 0.30.0 is the first version with a working --stdin --fix
+    if ale#semver#GTE(a:version, [0, 30, 0])
+        let l:project_root = ale#handlers#xo#GetProjectRoot(a:buffer)
+
         return {
-    \   'command': ale#node#Executable(a:buffer, l:executable)
+        \   'command': ale#path#CdString(l:project_root)
+        \       . l:executable
+        \       . ' --stdin --stdin-filename %s'
+        \       . ' --fix'
+        \       . l:options,
+        \}
+    endif
+
+    return {
+    \   'command': l:executable
     \       . ' --fix %t'
-    \       . ale#Pad(l:options),
+    \       . l:options,
     \   'read_temporary_file': 1,
     \}
 endfunction

autoload/ale/handlers/xo.vim

@@ -27,3 +27,9 @@ endfunction
 function! ale#handlers#xo#HandleJSON(buffer, lines) abort
     return ale#handlers#eslint#HandleJSON(a:buffer, a:lines)
 endfunction
+
+function! ale#handlers#xo#GetProjectRoot(buffer) abort
+    let l:package_path = ale#path#FindNearestFile(a:buffer, 'package.json')
+
+    return empty(l:package_path) ? '' : fnamemodify(l:package_path, ':p:h')
+endfunction

test/fixers/test_xo_fixer_callback.vader

@@ -29,3 +29,18 @@ Execute(The xo callback should include custom xo options):
   \     . ' --fix %t'
   \     . ' --space',
   \ }
+
+Execute(--stdin should be used when xo is new enough):
+  let g:ale_javascript_xo_options = '--space'
+  call ale#test#SetFilename('../eslint-test-files/react-app/subdir/testfile.js')
+
+  GivenCommandOutput ['0.30.0']
+  AssertFixer
+  \ {
+  \   'command': ale#path#CdString(ale#path#Simplify(g:dir . '/../eslint-test-files'))
+  \     . (has('win32') ? 'node.exe ' : '')
+  \     . ale#Escape(ale#path#Simplify(g:dir . '/../eslint-test-files/react-app/node_modules/xo/cli.js'))
+  \     . ' --stdin --stdin-filename %s'
+  \     . ' --fix'
+  \     . ' --space',
+  \ }

test/fixers/test_xots_fixer_callback.vader

@@ -29,3 +29,18 @@ Execute(The xo callback should include custom xo options):
   \     . ' --fix %t'
   \     . ' --space',
   \ }
+
+Execute(--stdin should be used when xo is new enough):
+  let g:ale_typescript_xo_options = '--space'
+  call ale#test#SetFilename('../eslint-test-files/react-app/subdir/testfile.ts')
+
+  GivenCommandOutput ['0.30.0']
+  AssertFixer
+  \ {
+  \   'command': ale#path#CdString(ale#path#Simplify(g:dir . '/../eslint-test-files'))
+  \     . (has('win32') ? 'node.exe ' : '')
+  \     . ale#Escape(ale#path#Simplify(g:dir . '/../eslint-test-files/react-app/node_modules/xo/cli.js'))
+  \     . ' --stdin --stdin-filename %s'
+  \     . ' --fix'
+  \     . ' --space',
+  \ }