Respect postcssrc (#7)

* Add support for postcssrc config file

* Ensure default options are persisted

* Fix support for static postcssrc config

* Documented postcssrc usage in README

README.md

@@ -61,6 +61,26 @@ add to your `package.json` `browserify.transform` field:
 }
 ```
 
+### using `.postcssrc`
+
+Options and plugins can be defined using a config file. Uses [postcss-load-config](https://github.com/michael-ciniawsky/postcss-load-config) which supports `postcss` field in `package.json`, an external JSON or YAML (`.postcssrc`) file as well as JS (`.postcssrc.js` and `postcss.config.js`) file format.
+
+```javascript
+// .postcssrc.js
+module.exports = function (ctx) {
+  var plugins = [require('postcss-color-function')]
+
+  if (ctx.env !== 'development') {
+    plugins.push(require('autoprefixer'))
+  }
+
+  return {
+    map: ctx.env === 'development' ? 'inline' : false
+    plugins: plugins
+  }
+}
+```
+
 ## license
 
 The Apache License

index.js

@@ -2,6 +2,7 @@ const defined = require('defined')
 const postcss = require('postcss')
 const extend = require('xtend')
 const resolve = require('resolve')
+const postcssrc = require('postcss-load-config')
 
 module.exports = transform
 
@@ -23,19 +24,25 @@ function transform (filename, source, options, done) {
     })
     .map(plugin => require(plugin.path)(plugin.options))
 
-  postcss(plugins)
-    .process(source, extend({
-      sourcemap: true,
-      from: filename,
-      messages: {
-        browser: true,
-        console: false
-      }
-    }, options))
-    .then(function (result) {
-      done(null, result.css)
-    })
-    .catch(function (err) {
-      done(err)
-    })
+  const ctx = extend({
+    sourcemap: true,
+    from: filename,
+    messages: {
+      browser: true,
+      console: false
+    }
+  }, options)
+
+  delete ctx.plugins
+
+  postcssrc(ctx, basedir).then(compile, function () {
+    return compile({options: ctx})
+  }).then(function (result) {
+    done(null, result.css)
+  }, done)
+
+  function compile (config) {
+    return postcss(plugins.concat(config.plugins).filter(Boolean))
+      .process(source, config.options)
+  }
 }

package.json

@@ -34,6 +34,7 @@
   "dependencies": {
     "defined": "^1.0.0",
     "postcss": "^5.1.2",
+    "postcss-load-config": "^1.2.0",
     "resolve": "^1.1.7",
     "xtend": "^4.0.1"
   }

test/index.js

@@ -1,3 +1,4 @@
+const path = require('path')
 const test = require('tape')
 const sheetifyPostcss = require('../')
 
@@ -19,5 +20,14 @@ test(function (t) {
       t.equal(css, '.ok-with-options {}')
     })
   })
+
+  t.test('module should respect postcssrc config file', function (t) {
+    t.plan(2)
+
+    sheetifyPostcss('test.css', '.rule {}', { basedir: path.join(__dirname, 'stubs') }, (err, css) => {
+      t.equal(err, null)
+      t.equal(css, '.ok-with-postcssrc {}')
+    })
+  })
 })
 

test/stubs/.postcssrc.js

@@ -0,0 +1,13 @@
+var postcss = require('postcss')
+
+var plugin = postcss.plugin('postcss-plugin', function postcssPlugin () {
+  return function (root, result) {
+    root.walkRules('.rule', rule => {
+      rule.replaceWith(postcss.rule({ selector: '.ok-with-postcssrc' }))
+    })
+  }
+})
+
+module.exports = {
+  plugins: [plugin]
+}