fix(doc-gen): correctly transform index files

Closes #3021

1 files changed, 7 insertions, 1 deletions

diff --git a/docs/src/writer.js b/docs/src/writer.js
index c9089be0..cdfa12d6 100644
--- a/docs/src/writer.js
+++ b/docs/src/writer.js
@@ -51,13 +51,19 @@ exports.copyTemplate = function(filename) {
  * @param  transform{function=} transfromation function to be applied before return
  */
 exports.copy = function(from, to, transform) {
+  var transformArgs = Array.prototype.slice.call(arguments, 3);
+
   from = pathUtils.normalize(from);
   to = pathUtils.normalize(to);
 
   // We have to use binary reading, Since some characters are unicode.
   return qfs.read(from, 'b').then(function(content) {
     if (transform) {
-      content = transform.call(null, content.toString(), from, to, transform);
+      // Pass any extra arguments, e.g.
+      // `copy(from, to, transform, extra1, extra2, ...)`
+      // to the transform function
+      transformArgs.unshift(content.toString());
+      content = transform.apply(null, transformArgs);
     }
     return output(to, content);
   });