Not getting errors when field present in class is not present on JSON when parsing

[marlon-sousa]

Hello,

I am having an unexpected behavior when parsing, at least as far as I can understand the documentation.

When a required @jsonMember field in class is not present on Json, I expected to have a parse error.
Instead, I apparently got the field either as undefined or not present.

I tested versions from 1.5.0 to 1.8.0 and got the same results:

import "reflect-metadata";
import { jsonMember, jsonObject, TypedJSON } from "typedjson";




@jsonObject
class Response {
    @jsonMember
    // have to mark it with ! because we have no constructor
    id!: number;
    @jsonMember
    // have to mark it with ! because we have no constructor
    firstName!: string;
    @jsonMember
    // have to mark it with ! because we have no constructor
    lastName!: string;
}

const serializer = new TypedJSON(Response);
serializer.config({
    errorHandler: e => { throw e; },
});
const resp = serializer.parse(`{
        "id": 1,
        "firstName": "a",
        "lavstName": "xx",
        "bla": "aaa"
}`);
console.log(resp);

As you can see, we expect a lastName field in the class but JSON has a lavstName, so the @jsonMember lastName is not provided.

I expected an error, but instead I got a Response class with id and firstName set, lastName not set.
The output of this script for me is this:

Response { id: 1, firstName: 'a', lastName: undefined }

I have tried to remove the ! of fields and to create an assignment constructor, with the same response.

To summarize ... my use case is simple:I want to make sure that a given JSON matches the specs of a given class, by specs I mean that all fields listed in the class are present and have the same types also on JSON, although JSON can perfectly contain more fields than the class.

Am I doing something wrong or this library doesn't help in these cases?

[marlon-sousa]

I forgot to mention that if lastName exists on JSON but its type is not the expected type of JSON ember, then I got an error as expected.

[sumbricht]

For anyone blocked by TypedJSON issues: my own software heavily relied on TypedJSON and had to apply numerous hacks for issues in TypedJSON that are not getting fixed. I loved TypedJSON but unfortunately had to move on as there has not been a single fix in 4 years now.

Therefore I created the similarly powerful library json-class-serializer heavily inspired by TypedJSON, which addresses all my issues (and hopefully yours). It's pretty much a drop-in replacement if you don't rely on reflect-metadata, which I'm not supporting (as this was the cause of most of my issues). If you rely on reflect-metadata, just specify the constructors of properties other than string/number/boolean and then it most likely just works.

Please feel free to give it a try if you feel the urge to move away from TypedJSON but don't want to do any heavy re-engineering. And please don't hate on me for the advertisement here as I have contributed to TypedJSON as well and opened many still-open issues :-).

You can find my library at @sumbricht/json-class-serializer and gladly open issues there if you feel something's missing / not working correctly.