add filter option to applyTransforms (#456)

lib/environment.js

@@ -34,6 +34,8 @@ const {
   createYoResolveTransform
 } = require('./util/transform');
 
+const {isFilePending} = FileEditor.State;
+
 /**
  * Two-step argument splitting function that first splits arguments in quotes,
  * and then splits up the remaining arguments if they are not part of a quote.
@@ -1230,12 +1232,13 @@ class Environment extends Base {
   /**
    * Apply transform streams to file in MemFs.
    * @param {Transform[]} transformStreams - transform streams to be applied.
-   * @param {Stream} [stream] - files stream, defaults to this.sharedFs.stream().
+   * @param {{ streamOptions: any; stream: Stream; name: string; log: boolean }} [options] - files stream, defaults to this.sharedFs.stream().
    * @return {Promise}
    */
   applyTransforms(transformStreams, options = {}) {
     const {
-      stream = this.sharedFs.stream(),
+      streamOptions = {filter: file => isFilePending(file)},
+      stream = this.sharedFs.stream(streamOptions),
       name = 'Transforming'
     } = options;