JSON object scalar

[nitsky]

Hi, I would like to create a custom scalar that serializes as a JSON object. @tyranron is this feasible with the v0.15 API, or are #1072 and #975 necessary for this?

I am hoping to be able to implement a GraphQL server like this:

scalar Point

type Query {
  location: Point
}

#[derive(serde::Serialize)]
struct Point {
  x: f32,
  y: f32,
}

[tyranron]

@nitsky yes, for having fields in GraphQL scalar like this we need to finish #1072 and #975 first, which is definitely 0.16 and onwards.

But why not use GraphQLInputObject for this?

[nitsky]

This would work in the simple case of the Point example I gave, but the data structures I am dealing with have a complex serialization defined with serde including multiple levels of structs and enums, and I don't want to allow users of my API to attempt to query a subset of the fields, it's either all or nothing, so a scalar is the most appropriate. Is serializing JSON to a string my only option until #1072 and #975 land?

[ilslv]

@nitsky

I don't want to allow users of my API to attempt to query a subset of the fields, it's either all or nothing, so a scalar is the most appropriate.

If you want to just give users a lot of data without querying subsets of it, custom scalar is your best option. I don't see how support for serde_json would help here. This integration is more for dynamic schema which isn't defined strictly with Rust types.
0.16 also will land more ergonomic scalar macros.

[nitsky]

I guess my question is, can my custom scalar be a complex nested JSON value, which I serialize with serde? Does that make sense?

[tyranron]

@nitsky

Is serializing JSON to a string my only option until #1072 and #975 land?

Yes.

[tyranron]

@nitsky

I guess my question is, can my custom scalar be a complex nested JSON value, which I serialize with serde?

Something like this should work now:

#[derive(Deserialize, Serialize, GraphQLScalar)]
#[graphql(parse_token(String))]
struct MyCustomStruct {
    // a lot of fields...
}

impl MyCustomStruct {
    fn from_input<S: ScalarValue>(
        input: &InputValue<S>,
    ) -> Result<Self, String> {
        serde_json::from_str(input.as_string_value()).map_err(|e| e.to_string())
    }

    fn to_output<S: ScalarValue>(&self) -> Value<S> {
        serde_json::to_string(self).unwrap().into()
    }
}