Add fs.listAsync

spec/stdlib/fs-utils-spec.coffee

@@ -127,3 +127,25 @@ describe "fs", ->
     it "returns the paths with the specified extensions", ->
       path = require.resolve('fixtures/css.css')
       expect(fs.list(fs.resolveOnLoadPath('fixtures'), ['.css'])).toEqual [path]
+  describe ".listAsync(path, [extensions,] callback)", ->
+    paths = null
+
+    it "calls the callback with the absolute paths of entries within the given directory", ->
+      waitsFor (done) ->
+        fs.listAsync project.getPath(), (err, result) ->
+          paths = result
+          done()
+      runs ->
+        expect(paths).toContain project.resolve('css.css')
+        expect(paths).toContain project.resolve('coffee.coffee')
+        expect(paths).toContain project.resolve('two-hundred.txt')
+
+    it "can filter the paths by an optional array of file extensions", ->
+      waitsFor (done) ->
+        fs.listAsync project.getPath(), ['css', '.coffee'], (err, result) ->
+          paths = result
+          done()
+      runs ->
+        expect(paths).toContain project.resolve('css.css')
+        expect(paths).toContain project.resolve('coffee.coffee')
+        expect(path).toMatch /(css|coffee)$/ for path in paths

src/stdlib/fs-utils.coffee

@@ -93,6 +93,19 @@ module.exports =
     @traverseTreeSync(rootPath, onPath, onPath)
     paths
 
+  listAsync: (rootPath, rest...) ->
+    extensions = rest.shift() if rest.length > 1
+    done = rest.shift()
+    fs.readdir rootPath, (err, paths) =>
+      return done(err) if err
+      paths = @filterExtensions(paths, extensions) if extensions
+      paths = paths.map (path) => @join(rootPath, path)
+      done(null, paths)
+
+  filterExtensions: (paths, extensions) ->
+    extensions = extensions.map (ext) -> '.' + ext.replace(/^\./, '')
+    paths.filter (path) => _.include(extensions, @extension(path))
+
   listTree: (rootPath) ->
     paths = []
     onPath = (path) =>