Inferring the syntax of unknow file

.gitignore

@@ -1,2 +1,4 @@
 node_modules
 npm-debug.log
+.nyc_output/
+coverage/

README.md

@@ -302,7 +302,7 @@ $ cat input.css | stylefmt --stdin-filename input.css
 ```js
 var fs = require('fs');
 var postcss = require('postcss');
-var scss = require('postcss-scss'); // when you use scss syntax
+var syntax = require('postcss-html'); // when you use non-standard syntax
 var stylefmt = require('stylefmt');
 
 var css = fs.readFileSync('input.css', 'utf-8');
@@ -311,7 +311,7 @@ postcss([
   stylefmt
 ]).process(css, {
     from: 'input.css',
-    syntax: scss
+    syntax: syntax
   })
   .then(function (result) {
     result.css; // formatted code

bin/cli.js

@@ -24,7 +24,7 @@ var argv = minimist(process.argv.slice(2), {
 })
 
 var postcss = require('postcss')
-var scss = require('postcss-scss')
+var syntax = require('postcss-html')
 
 if (argv.v) {
   console.log(pkg.version)
@@ -76,7 +76,7 @@ if (argv.r) {
   postcss([stylefmt(options)])
     .process(css, {
       from: fullPath,
-      syntax: scss
+      syntax: syntax
     })
     .then(function (result) {
       var formatted = result.css
@@ -98,7 +98,7 @@ if (argv.r) {
     postcss([stylefmt(options)])
       .process(css, {
         from: options.codeFilename,
-        syntax: scss
+        syntax: syntax
       })
       .then(function (result) {
         process.stdout.write(result.css)
@@ -122,7 +122,7 @@ function processMultipleFiles (files) {
     return postcss([stylefmt(options)])
       .process(css, {
         from: fullPath,
-        syntax: scss
+        syntax: syntax
       })
       .then(function (result) {
         var formatted = result.css
@@ -156,7 +156,7 @@ function processMultipleFiles (files) {
 
 
 function isCss (filePath) {
-  return /^\.css|\.less|\.pcss|\.scss|\.wxss$/i.test(path.extname(filePath))
+  return /^\.(?:vue|html?|(?:(?:[ps]?c)|le|wx|sa?)ss)$/i.test(path.extname(filePath))
 }
 
 

package.json

@@ -37,12 +37,16 @@
     "globby": "^6.1.0",
     "minimist": "^1.2.0",
     "postcss": "^6.0.1",
+    "postcss-html": "^0.4.0",
+    "postcss-less": "^1.0.1",
+    "postcss-sass": "^0.1.0",
     "postcss-scss": "^1.0.0",
     "postcss-sorting": "^2.1.0",
     "postcss-value-parser": "^3.3.0",
     "stdin": "^0.0.1",
     "stylelint": "^7.10.1",
-    "stylelint-order": "^0.4.4"
+    "stylelint-order": "^0.4.4",
+    "sugarss": "^1.0.0"
   },
   "devDependencies": {
     "each-series": "^1.0.0",