"sanity check" for cloud-saving mechanism

errors if the serialized project data is corrupt and cannot be parsed
as XML, addresses #203, #200, #171. I'm hoping that this might provide
us a clue whether the corruption is happening in Snap's marshalling or
on the backend side

cloud.js

@@ -29,7 +29,7 @@
 
 /*global modules, IDE_Morph, SnapSerializer, hex_sha512, alert, nop*/
 
-modules.cloud = '2013-September-17';
+modules.cloud = '2013-October-10';
 
 // Global stuff
 
@@ -356,6 +356,24 @@ Cloud.prototype.saveProject = function (ide, callBack, errorCall) {
     ide.serializer.isCollectingMedia = false;
     ide.serializer.flushMedia();
 
+    // check if serialized data can be parsed back again
+    try {
+        ide.serializer.parse(pdata);
+    } catch (err) {
+        ide.showMessage('Serialization of program data failed:\n' + err);
+        throw new Error('Serialization of program data failed:\n' + err);
+    }
+    if (media !== null) {
+        try {
+            ide.serializer.parse(media);
+        } catch (err) {
+            ide.showMessage('Serialization of media failed:\n' + err);
+            throw new Error('Serialization of media failed:\n' + err);
+        }
+    }
+    ide.serializer.isCollectingMedia = false;
+    ide.serializer.flushMedia();
+
     myself.reconnect(
         function () {
             myself.callService(

history.txt

@@ -1950,3 +1950,7 @@ ______
 131009
 ------
 * Theads: added a variant for linked lists to the experimental MAP primitive reporter
+
+131010
+------
+* Cloud: added "sanity check" to cloud-saving mechanism that errors if the serialized project data is corrupt and cannot be parsed as XML, addresses #203, #200, #171