Model: the order of 'convert' fields can be broken

[natb]

REQUIRED INFORMATION
Ext version tested:

• Sencha 2.1

Browser versions tested against:

• Chrome 23.0

Description:

• Sencha applies sorting to Model fields based on 'covert' function existence in order to ensure that fields with 'convert' are at the bottom.
  
  But it seems that in some cases sorting can reorder equal items thus breaking initially configured order and dependencies between 'convert' fields.
  
  It seems there is no need to apply sorting to fields array and enough to go through all fields once moving 'non-convert' fields to the top. This would keep the order of 'convert' fields.

Steps to reproduce the problem:

• Create model as in the test case with 'convert' fields depending each other -> view fields array, the order of 'convert' fields is different to the configured order.
• Create a record of that model -> error appears because some of expected fields are not set yet.

Test Case:

 Ext.define('User', {
    extend: 'Ext.data.Model',


    config: {
        fields: [
            { name: 'first_name', type: 'string' },
            { name: 'first_name2', type: 'string' },
            { name: 'first_name3', type: 'string' },
            { name: 'first_name4', type: 'string' },
            { name: 'first_name5', type: 'string' },
            { name: 'first_name6', type: 'string' },
            
            { name: 'last_name', type: 'string' },
            
            { name: 'letters1',
                convert: function (v, record) {
                    return record.get('last_name').substr(0, 2);
                }
            },
            { name: 'letters2',
                convert: function (v, record) {
                    return record.get('letters1').substr(0, 1);
                }
            },
            { name: 'letters4',
                convert: function (v, record) {
                    return record.get('letters1').substr(0, 1);
                }
            },
            { name: 'letters5',
                convert: function (v, record) {
                    return record.get('letters1').substr(0, 1);
                }
            },
            { name: 'letters6',
                convert: function (v, record) {
                    return record.get('letters1').substr(0, 1);
                }
            },
            { name: 'letters7',
                convert: function (v, record) {
                    return record.get('letters1').substr(0, 1);
                }
            }
        ]
    }
});

User.getFields().keys // fields are reordered: id is added at position 1, first_name2 is moved to position 7, letters1 is moved to bottom position 13 so that letters2, letters3, etc can't be properly set now


var user = Ext.create('User', {
    first_name: 'Ed',
    last_name: 'Spencer'
});  // -> Error; Cannot call method 'substr' of undefined

[mitchellsimoens]

Thanks for the report! I have opened a bug in our bug tracker.