Define 'system metadata' which should not be editable by the end user. When posting back metadata edits, we need to fetch a copy of the existing metadata and apply the changes.

cms/djangoapps/contentstore/views.py

@@ -104,6 +104,7 @@ def edit_item(request):
 
     item = modulestore().get_item(item_location)
     item.get_html = wrap_xmodule(item.get_html, item, "xmodule_edit.html")
+
     return render_to_response('unit.html', {
         'contents': item.get_html(),
         'js_module': item.js_module_name,
@@ -287,8 +288,16 @@ def save_item(request):
 
     # cdodge: also commit any metadata which might have been passed along in the
     # POST from the client, if it is there
+    # note, that the postback is not the complete metadata, as there's system metadata which is
+    # not presented to the end-user for editing. So let's fetch the original and
+    # 'apply' the submitted metadata, so we don't end up deleting system metadata
     if request.POST['metadata']:
-        modulestore().update_metadata(item_location, request.POST['metadata'])
+        posted_metadata = request.POST['metadata']
+        # fetch original
+        existing_item = modulestore().get_item(item_location)
+        # update existing metadata with submitted metadata (which can be partial)
+        existing_item.metadata.update(posted_metadata)
+        modulestore().update_metadata(item_location, existing_item.metadata)
 
     # Export the course back to github
     # This uses wildcarding to find the course, which requires handling

cms/templates/widgets/metadata-edit.html

@@ -2,7 +2,7 @@
 <section class="metadata_edit">
   <h3>Metadata</h3>
   <ul>
-    % for keyname in metadata.keys():
+    % for keyname in editable_metadata_fields:
     <li>${keyname}: <input type='text' data-metadata-name='${keyname}' value='${metadata[keyname]}' size='60' /></li>
     % endfor
   </ul>

common/lib/xmodule/xmodule/editing_module.py

@@ -17,14 +17,13 @@ class EditingDescriptor(MakoModuleDescriptor):
     js = {'coffee': [resource_string(__name__, 'js/src/raw/edit.coffee')]}
     js_module_name = "RawDescriptor"
 
-    def get_context(self):
-        return {
-            'module': self,
-            'data': self.definition.get('data', ''),
-            'metadata': self.metadata
-    # TODO (vshnayder): allow children and metadata to be edited.
-    #'children' : self.definition.get('children, ''),
 
-    # TODO: show both own metadata and inherited?
-    #'metadata' : self.own_metadata,
-        }
+    # cdodge: a little refactoring here, since we're basically doing the same thing
+    # here as with our parent class, let's call into it to get the basic fields
+    # set and then add our additional fields. Trying to keep it DRY.
+    def get_context(self):
+        _context = MakoModuleDescriptor.get_context(self)
+        # Add our specific template information (the raw data body)
+        _context.update({ 'data' : self.definition.get('data','') })
+        return _context
+    

common/lib/xmodule/xmodule/mako_module.py

@@ -1,4 +1,5 @@
 from x_module import XModuleDescriptor, DescriptorSystem
+import logging
 
 
 class MakoDescriptorSystem(DescriptorSystem):
@@ -32,9 +33,17 @@ class MakoModuleDescriptor(XModuleDescriptor):
         Return the context to render the mako template with
         """
         return {'module': self,
-                'metadata': self.metadata
+                'metadata': self.metadata,
+                'editable_metadata_fields' : self.editable_metadata_fields
                 }
 
     def get_html(self):
         return self.system.render_template(
             self.mako_template, self.get_context())
+
+    # cdodge: encapsulate a means to expose "editable" metadata fields (i.e. not internal system metadata)
+    @property
+    def editable_metadata_fields(self):
+        subset = [name for name in self.metadata.keys() if name not in self.system_metadata_fields]
+        return subset
+

common/lib/xmodule/xmodule/x_module.py

@@ -352,6 +352,10 @@ class XModuleDescriptor(Plugin, HTMLSnippet):
         'data_dir'
     )
 
+    # cdodge: this is a list of metadata names which are 'system' metadata
+    # and should not be edited by an end-user
+    system_metadata_fields = [ 'data_dir' ]
+    
     # A list of descriptor attributes that must be equal for the descriptors to
     # be equal
     equality_attributes = ('definition', 'metadata', 'location',