From 34f83d991956ace694857cbd7170d09962cd3355 Mon Sep 17 00:00:00 2001
From: "Ryan L. Bell" <ryan.l.bell@gmail.com>
Date: Tue, 4 Oct 2016 15:02:32 -0400
Subject: [PATCH] Handle cases where DataTransfer has a null +files+ slot

---
 src/DOM/HTML/Event/DragEvent/DataTransfer.js   |  2 +-
 src/DOM/HTML/Event/DragEvent/DataTransfer.purs | 12 +++++++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/DOM/HTML/Event/DragEvent/DataTransfer.js b/src/DOM/HTML/Event/DragEvent/DataTransfer.js
index 9c95d84..0eee62e 100644
--- a/src/DOM/HTML/Event/DragEvent/DataTransfer.js
+++ b/src/DOM/HTML/Event/DragEvent/DataTransfer.js
@@ -1,6 +1,6 @@
 "use strict";
 
-exports.files = function (dataTransfer) {
+exports.filesNullable = function (dataTransfer) {
   return dataTransfer.files;
 };
 
diff --git a/src/DOM/HTML/Event/DragEvent/DataTransfer.purs b/src/DOM/HTML/Event/DragEvent/DataTransfer.purs
index 9792f6a..416ff44 100644
--- a/src/DOM/HTML/Event/DragEvent/DataTransfer.purs
+++ b/src/DOM/HTML/Event/DragEvent/DataTransfer.purs
@@ -1,16 +1,26 @@
 module DOM.HTML.Event.DragEvent.DataTransfer
   ( DataTransfer
   , files
+  , filesNullable
   , types
   ) where
 
+import Prelude
 import DOM.File.Types (FileList)
+import Data.Maybe (Maybe)
+import Data.Nullable (Nullable, toMaybe)
 
 foreign import data DataTransfer :: *
 
 -- | Contains a list of all the local files available on the data transfer.
 -- | Empty if the drag operation doesn't involve dragging files.
-foreign import files :: DataTransfer -> FileList
+-- |
+-- | It's possible that a drag operation may have null files, instead of an
+-- | empty file list. In these cases Nothing is returned.
+files :: DataTransfer -> Maybe FileList
+files = toMaybe <$> filesNullable
+
+foreign import filesNullable :: DataTransfer -> Nullable FileList
 
 -- | Returns an array of data formats used in the drag operation.
 -- | If the drag operation included no data, then the array is empty.