Ext Data Session and bad server response ("[W] Ignoring server record: ...") - session

Question

Our application handles and manages records changes on the client side. We use ExtJS5 Data Session mechanism.
A session tracks records that need to be updated, created or destroyed
on the server. It can also order these operations to ensure that newly
created records properly reference other newly created records by
their new, server-assigned id.
Let me introduce short use case.
User opens and fills a form. Behind the scene fields are binded to entity object which is tracked by session. When user clicks Submit then session is synchronized, i.e. Ext sends requests to the server and parse response. Here I've encountered a problem.
Server returns following object but Ext does not recognize it:
[{"success": false, errorMessage: "error"}]
Ext prints warning:
[W] Ignoring server record: {"success":false}
or
[W] Ignoring server record: {"success":true}
My question is how should look server response in order to indicate that record is not accepted/saved by backend?
The source code where above warning is printed: http://docs-origin.sencha.com/extjs/5.0/apidocs/source/Operation.html (in function doProcess)
Below I put snippet how I'm starting a batch operation (sync session):
var session = this.getViewModel().getSession(),
saveBatch = session.getSaveBatch();
saveBatch.on('complete', function (batch, operation, eOpts) {
// whole batch processing has been completed
/*...*/
});
saveBatch.on('exception', function (batch, operation, eOpts) {
// exception has been occurred (possible for each operation) (such as HTTP 500)
/*...*/
});
saveBatch.on('operationcomplete', function (batch, operation, eOpts) {
// single operation has been completed
// now, every operation is marked as successful
/*...*/
});
saveBatch.start();
update 26.09.2014
Sencha developer has suggested including an id of object in the response. so I've modified server response to:
[{"id": 10, "success": false}]
but this does not solve the problem.

Answer 1

I spend some time on debugging Ext.data.operation.Operation.doProcess method and I analyzed a sample code from sencha support. Ultimately I've found the solution.
There is my proxy config:
proxy: {
type: 'rest',
// ...
reader: {
type: 'json',
rootProperty: 'data',
totalProperty: 'totalCount',
successProperty: 'success',
messageProperty: 'errorMessage'
}
}
Server response when some error occured:
{
"success": false,
"errorMessage": "<error message>"
}
Server response when data was successfully saved:
The minimal form for delete or update record without changing data:
{
"success": true,
}
The extended form for creating or updating record with changing record data:
{
"success": true,
"data": [{
clientId: 5, // clientIdProperty
id: 5,
// [optional] fields to change, e.g.:
name: 'new name'
}]
}
I modified a demo which I have from sencha support:
https://fiddle.sencha.com/#fiddle/bem
in proxy config use data2.json for error and data3.json for success response.