Per file config, context for postcss-config-loader

Author: Andrey Kuzmin

README.md

@@ -49,18 +49,18 @@ gulp.task('css', function () {
 
 The second optional argument to gulp-postcss is passed to PostCSS.
 
-This, for instance, may be used to enable custom syntax:
+This, for instance, may be used to enable custom parser:
 
 ```js
 var gulp = require('gulp');
 var postcss = require('gulp-postcss');
 var nested = require('postcss-nested');
-var scss = require('postcss-scss');
+var sugarss = require('sugarss');
 
 gulp.task('default', function () {
     var plugins = [nested];
-    return gulp.src('in.css')
-        .pipe(postcss(plugins, {syntax: scss}))
+    return gulp.src('in.sss')
+        .pipe(postcss(plugins, { parser: sugarss }))
         .pipe(gulp.dest('out'));
 });
 ```
@@ -105,6 +105,65 @@ return gulp.src('./src/*.css')
     .pipe(gulp.dest('./dest'));
 ```
 
+## Advanced usage
+
+If you want to configure per file basis, you can pass a callback that
+receives [vinyl file object](https://github.com/gulpjs/vinyl) and returns
+`{ plugins: plugins, options: options }`. For example, when you need to
+parse different extensions differntly:
+
+```js
+var gulp = require('gulp');
+var postcss = require('gulp-postcss');
+
+gulp.task('css', function () {
+    function callback(file) {
+        return {
+            plugins: [
+                require('postcss-import')({ root: file.dirname }),
+                require('postcss-modules')
+            ],
+            options: {
+                parser: file.extname === '.sss' ? require('sugarss') : false
+            }
+        }
+    }
+    return gulp.src('./src/*.css')
+        .pipe(postcss(callback))
+        .pipe(gulp.dest('./dest'));
+});
+```
+
+The same result may be achieved with
+[`postcss-load-config`](https://www.npmjs.com/package/postcss-load-config),
+because it receives `ctx` with the context options and the vinyl file.
+
+```js
+var gulp = require('gulp');
+var postcss = require('gulp-postcss');
+
+gulp.task('css', function () {
+    var contextOptions = { modules: true };
+    return gulp.src('./src/*.css')
+        .pipe(postcss(contextOptions))
+        .pipe(gulp.dest('./dest'));
+});
+```
+
+```js
+module.exports = function (ctx) {
+    var file = ctx.file;
+    var options = ctx.options;
+    return {
+        parser: file.extname === '.sss' ? : 'sugarss' : false,
+        plugins: {
+           'postcss-import': { root: file.dirname }
+           'postcss-modules': options.modules ? {} : false
+        }
+    }
+})
+```
+
 ## Changelog
 
 * 6.2.0

index.js

@@ -3,7 +3,6 @@ var postcss = require('postcss')
 var applySourceMap = require('vinyl-sourcemaps-apply')
 var gutil = require('gulp-util')
 var path = require('path')
-var postcssLoadConfig = require('postcss-load-config')
 
 
 module.exports = withConfigLoader(function (loadConfig) {
@@ -32,11 +31,7 @@ module.exports = withConfigLoader(function (loadConfig) {
     , map: file.sourceMap ? { annotation: false } : false
     }
 
-    loadConfig({
-      from: options.from
-    , to: options.to
-    , map: options.map
-    })
+    loadConfig(file)
       .then(function (config) {
         var configOpts = config.options || {}
         // Extend the default options if not protected
@@ -102,20 +97,25 @@ module.exports = withConfigLoader(function (loadConfig) {
 
 function withConfigLoader(cb) {
   return function (plugins, options) {
-    if (typeof plugins === 'undefined') {
-      return cb(postcssLoadConfig)
-    } else if (Array.isArray(plugins)) {
+    if (Array.isArray(plugins)) {
       return cb(function () {
         return Promise.resolve({
           plugins: plugins
         , options: options
         })
       })
+    } else if (typeof plugins === 'function') {
+      return cb(function (file) {
+        return Promise.resolve(plugins(file))
+      })
     } else {
-      throw new gutil.PluginError(
-        'gulp-postcss',
-        'Please provide array of postcss processors!'
-      )
+      var postcssLoadConfig = require('postcss-load-config')
+      return cb(function(file) {
+        return postcssLoadConfig({
+          file: file
+        , options: plugins
+        })
+      })
     }
   }
 }

test.js

@@ -92,13 +92,6 @@ it('should respond with error on stream files', function (cb) {
 
 })
 
-
-it('should throw error if plugins are not array', function () {
-  assert.throws( function () { postcss('') }, gutil.PluginError )
-  assert.throws( function () { postcss({}) }, gutil.PluginError )
-})
-
-
 it('should generate source maps', function (cb) {
 
   var init = sourceMaps.init()
@@ -175,8 +168,8 @@ describe('PostCSS Guidelines', function () {
       postcssStub.use(plugins)
       return postcssStub
     }
-  , 'postcss-load-config': function (args) {
-      return postcssLoadConfigStub(args)
+  , 'postcss-load-config': function (ctx) {
+      return postcssLoadConfigStub(ctx)
     }
   , 'vinyl-sourcemaps-apply': function () {
       return {}
@@ -242,10 +235,46 @@ describe('PostCSS Guidelines', function () {
 
   })
 
+  it('should take plugins and options from callback', function (cb) {
+
+    var cssPath = __dirname + '/fixture.css'
+    var file = new gutil.File({
+      contents: new Buffer('a {}')
+    , path: cssPath
+    })
+    var plugins = [ doubler ]
+    var callback = sandbox.stub().returns({
+      plugins: plugins
+    , options: { to: 'overriden' }
+    })
+    var stream = postcss(callback)
+
+    postcssStub.process.returns(Promise.resolve({
+      css: ''
+    , warnings: function () {
+        return []
+      }
+    }))
+
+    stream.on('data', function () {
+      assert.equal(callback.getCall(0).args[0], file)
+      assert.equal(postcssStub.use.getCall(0).args[0], plugins)
+      assert.equal(postcssStub.process.getCall(0).args[1].to, 'overriden')
+      cb()
+    })
+
+    stream.end(file)
+
+  })
+
   it('should take plugins and options from postcss-load-config', function (cb) {
 
     var cssPath = __dirname + '/fixture.css'
-    var stream = postcss()
+    var file = new gutil.File({
+      contents: new Buffer('a {}')
+    , path: cssPath
+    })
+    var stream = postcss({ to: 'initial' })
     var plugins = [ doubler ]
 
     postcssLoadConfigStub.returns(Promise.resolve({
@@ -262,21 +291,15 @@ describe('PostCSS Guidelines', function () {
 
     stream.on('data', function () {
       assert.deepEqual(postcssLoadConfigStub.getCall(0).args[0], {
-        from: cssPath
-      , to: cssPath
-      , map: false
+        file: file
+      , options: { to: 'initial' }
       })
       assert.equal(postcssStub.use.getCall(0).args[0], plugins)
       assert.equal(postcssStub.process.getCall(0).args[1].to, 'overriden')
       cb()
     })
 
-    stream.write(new gutil.File({
-      contents: new Buffer('a {}')
-    , path: cssPath
-    }))
-
-    stream.end()
+    stream.end(file)
 
   })