Type erasure and support for mixed

[tmarzec]

The problem

The communication between the device and the desktop side is done by sockets. before it's sent over (both ways), the data has to be serialized. The serialization process modifies the objects and erases some of the information.
For example, the Realm.UUID type is converted to a string, and inner realm objects (the ones with property { type: 'object', objectType: '...' }) lose all the functions, connecting them to existing schemas (objectSchema function).
This problem has consequences, that can be split into two parts:

Mixed types

When mixed values belonging to Realm are sent over, the real type is lost. There is no difference between UUID('aa79b9ed-fbc0-4038-8f16-31f4da3efb9e') and string 'aa79b9ed-fbc0-4038-8f16-31f4da3efb9e'. The same problem happens when we assign linked objects to mixed properties. There is no way to find out to which schema the object belongs, since the objectSchema function is lost.

Non-mixed type erasure

Consider a simple schema:

{
    name: 'schemaName',
    properties: {
        propName: 'uuid',  
    },
}

When sending that object between the device and the desktop, all the properties can be correctly converted upon receiving, since we can retrieve their correct type from the properties object. Also, containers can be properly handled.

Current solution

Right now non-mixed type conversion is only done when receiving the data on the device, in realm-flipper-plugin-device/src/ConvertFunctions.tsx file. That way of doing things is not perfect, since it only works for non-mixed types when the type is saved outside of the object being transferred.

My opinion on the ideal solution

Ideally, the properties of all the objects before sending via sockets should be wrapped with a type description (potentially like in MongoDB extended JSON).

This works nicely because this can save all the information about a value before it is serialized. Then, when receiving an object, it can be decoded and converted to a valid type. This would also work for con trivially serializable values in mixed properties.

The previously mentioned library (extended JSON) could be used, but with minor improvements:

• data has to be handled properly
• UUID seems to be not supported
• on the desktop side: objects have to be kept together with their schema at all times