Support string argument

Author: zoubin

README.md

@@ -20,7 +20,8 @@ var fixtures = path.resolve.bind(path, __dirname, 'fixtures')
 
 postcss(url([
   [ util.inline, { maxSize: 5 } ],
-  [ util.copy, { assetOutFolder: fixtures('build', 'images') } ],
+  // equivalent with util.copy
+  [ 'copy', { assetOutFolder: fixtures('build', 'images') } ],
 ]))
 .process(
   '.a{ background-image: url(images/octocat_setup.png); }',

lib/result.js

@@ -3,6 +3,7 @@
 const Url = require('url')
 const path = require('path')
 const Asset = require('./asset')
+const util = require('./util')
 
 class Result {
   constructor(url, opts) {
@@ -46,6 +47,9 @@ class Result {
     })
     return trs.reduce(function (p, tr) {
       return p.then(function () {
+        if (typeof tr[0] === 'string') {
+          tr[0] = util[tr[0]]
+        }
         let r = tr[0].apply(null, tr.slice(1))
         if (r && typeof r.then === 'function') {
           return r

test/custom.js

@@ -18,7 +18,7 @@ test('custom', function(t) {
 
       result.url = path.join(base, path.basename(result.url))
     }, 'i'],
-    util.copy,
+    'copy',
   ])
   let body = '.a{ background-image: url(images/octocat_setup.png) url(images/octocat_fork.png); }'
   let expectedBody = [ '.a{background-image:url(', ')url(i/octocat_fork.png);}' ]