Typed JSON

[Palmik]

It would be nice and useful to have types generated for objects produced by toJson, rather than just having a generic type like today.

[smaye81]

Hi @Palmik this has been requested a few times. It's probably something we should consider. Going to keep this open so we can eventually prioritize.

[FND]

FWIW, I've run into the same issue and resorted to deriving data structures from classes. However, that's not just brittle, it also feels like solving the problem at the wrong layer because the compiler should already know what these data structures look like.

source code

// given the following class hierarchy...

import { Message } from "@bufbuild/protobuf";

class Person extends Message<Person> {
    name?: string;
    age?: number;
    address?: Address;
}

class Address extends Message<Address> {
    country?: string;
    location?: string;
}

// ... we want to generate a type containing only the respective data fields

let data: PersonData = {
    name: "JD",
    age: 123,
    address: {
        country: "Nirvana",
        location: "ether"
    }
};

// ... so we derive data structures from the respective classes

type PersonData = DataOnly<Person>;
type AddressData = DataOnly<Address>; // for testing purposes only

type DataOnly<T extends OptionalMessage> = T extends Message ? {
        [Key in Exclude<keyof T, keyof Message>]: T[Key] extends OptionalMessage
            ? DataOnly<T[Key]>
            : T[Key];
    }
    : undefined;
type OptionalMessage = Message | undefined;

// ... except properties' optional flag is lost

data = {
    name: "JD",
    age: 123
};

[Zetanova]

I run into an issue with IndexedDb used over dexie.js

To use a generic JsonValue inside the stored data type then the the query and patch feature of dexie is not type-safe.

The PlainMessage<MyMessage> is useable (not optimal) but brings other issues
dexie/Dexie.js#2001

To generate a typed Interface for the JsonValue with the correct used json_name would be optimal in this regard.