Allow transforms to return a { css, files } object (#147)

* Allow transforms to return a `{ css, files }` object

`'file'` events will be emitted for each file listed in `files`.

* Fix lint

Author: goto-bus-stop

index.js

@@ -64,15 +64,15 @@ function parseCss (src, filename, prefix, options, done) {
   assert.equal(typeof options, 'object', 'options must be a object')
   assert.equal(typeof done, 'function', 'done must be a function')
 
-  applyTransforms(filename, String(src), xtend(options), function (err, css) {
+  applyTransforms(filename, String(src), xtend(options), function (err, result) {
     if (err) return done(err)
     var p = postcss()
     p = p.use(cssPrefix('.' + prefix))
 
     try {
-      css = p.process(css).toString()
+      result.css = p.process(result.css).toString()
 
-      return done(null, css, prefix)
+      return done(null, result, prefix)
     } catch (e) {
       return done(e)
     }
@@ -82,9 +82,10 @@ function parseCss (src, filename, prefix, options, done) {
   // one at the time
   // (str, str, obj, fn) -> null
   function applyTransforms (filename, src, options, done) {
+    var current = { css: src, files: [] }
     mapLimit(options.transform, 1, iterate, function (err) {
       if (err) return done(err)
-      done(null, src)
+      done(null, current)
     })
 
     // find and apply a transform to a string of css
@@ -106,9 +107,14 @@ function parseCss (src, filename, prefix, options, done) {
         if (err) return done(err)
 
         const transform = require(transformPath)
-        transform(filename, src, opts, function (err, result) {
+        transform(filename, current.css, opts, function (err, result) {
           if (err) return next(err)
-          src = result
+          if (typeof result === 'string') {
+            current.css = result
+          } else {
+            current.css = result.css
+            current.files = current.files.concat(result.files)
+          }
           next()
         })
       })

test/fixtures/files-plugin.js

@@ -0,0 +1,6 @@
+module.exports = function (file, source, opts, done) {
+  done(null, {
+    css: '.test {}',
+    files: [opts.file]
+  })
+}

test/plugins.js

@@ -55,4 +55,39 @@ test('plugins', function (t) {
         t.end()
       }))
   })
+
+  t.test('should emit \'file\' events if transform included more files', function (t) {
+    const bpath = path.join(__dirname, 'fixtures/plugins-source.js')
+    const bOpts = { browserField: false }
+    const expectedFiles = [
+      bpath,
+      '/path/to/included/file.css'
+    ]
+    const actualFiles = []
+    browserify(bpath, bOpts)
+      .transform(sheetify, {
+        transform: [
+          [ require.resolve('./fixtures/files-plugin'), {
+            file: '/path/to/included/file.css'
+          } ]
+        ]
+      })
+      .exclude('sheetify/insert')
+      .on('file', onfile)
+      .on('transform', ontransform)
+      .bundle(function (err, result) {
+        t.ifError(err)
+        t.deepEqual(actualFiles.sort(), expectedFiles.sort())
+        t.end()
+      })
+
+    function onfile (filename) {
+      if (actualFiles.indexOf(filename) === -1) {
+        actualFiles.push(filename)
+      }
+    }
+    function ontransform (tr) {
+      tr.on('file', onfile)
+    }
+  })
 })

transform.js

@@ -202,10 +202,10 @@ function transform (filename, options) {
     }
 
     function handleCss (val) {
-      sheetify(val.css, val.filename, val.opts, function (err, css, prefix) {
+      sheetify(val.css, val.filename, val.opts, function (err, result, prefix) {
         if (err) return done(err)
         const str = [
-          "((require('sheetify/insert')(" + JSON.stringify(css) + ')',
+          "((require('sheetify/insert')(" + JSON.stringify(result.css) + ')',
           ' || true) && ' + JSON.stringify(prefix) + ')'
         ].join('')
 
@@ -215,6 +215,11 @@ function transform (filename, options) {
           ? ''
           : ';'
         val.node.update(lolSemicolon + str)
+
+        result.files.forEach(function (includedFile) {
+          transformStream.emit('file', includedFile)
+        })
+
         done()
       })
     }