Simplify file submission front end

common/lib/xmodule/xmodule/js/src/capa/display.coffee

@@ -67,16 +67,14 @@ class @Problem
 
     fd = new FormData()
 
-    # For each file input, allow a single file submission,
-    #   which is routed to Django 'request.FILES'
-    @$('input:file').each (index, element) ->
+    @$("[id^=input_#{@element_id.replace(/problem_/, '')}_]").each (index, element) ->
+      if element.type is 'file'
         if element.files[0] instanceof File
           fd.append(element.id, element.files[0])
         else
-        fd.append(element.id, '')  # Even if no file selected, need to include input id
-
-    # Simple (non-file) answers, which is routed to Django 'request.POST'
-    fd.append('__answers_querystring', @answers)
+          fd.append(element.id, '')
+      else
+        fd.append(element.id, element.value)
 
     settings = 
       type: "POST"

lms/djangoapps/courseware/module_render.py

 import json
 import logging
-from urlparse import parse_qs
 
 from django.conf import settings
 from django.http import Http404
@@ -273,22 +272,10 @@ def modx_dispatch(request, dispatch=None, id=None):
     # ''' (fix emacs broken parsing)
 
     # Check for submitted files
-    post = dict()
+    p = request.POST.copy()
     if request.FILES:
         for inputfile_id in request.FILES.keys():
-            post[inputfile_id] = request.FILES[inputfile_id]
-
-    # Catch the use of FormData in xmodule frontend for 'problem_check'. After this block,
-    #   the 'post' dict is functionally equivalent before and after the use of FormData
-    # TODO: A more elegant solution?
-    for key in request.POST.keys():
-        if key == '__answers_querystring':
-            qs = request.POST.get(key)
-            qsdict = parse_qs(qs, keep_blank_values=True)
-            for qskey in qsdict.keys():
-                post[qskey] = qsdict[qskey][0] # parse_qs returns {key: list}
-        else:
-            post[key] = request.POST.get(key)
+            p[inputfile_id] = request.FILES[inputfile_id]
 
     student_module_cache = StudentModuleCache(request.user, modulestore().get_item(id))
     instance, instance_module, shared_module, module_type = get_module(request.user, request, id, student_module_cache)
@@ -301,7 +288,7 @@ def modx_dispatch(request, dispatch=None, id=None):
 
     # Let the module handle the AJAX
     try:
-        ajax_return = instance.handle_ajax(dispatch, post)
+        ajax_return = instance.handle_ajax(dispatch, p)
     except NotFoundError:
         log.exception("Module indicating to user that request doesn't exist")
         raise Http404