Property resolver with context

[StefanLiebig]

While it is possible to pass an optional context object to the "execute" function of the Schema which than will be propagated to the "suspendResolver"/"resolver" functions of the "query" block, I have not found a way how this context object gets passed to the property resolvers.

(using version 0.3.0)

[shamresh]

Can you give a use case of where this would be used? (I am new to GraphQL and Kotlin :))

[StefanLiebig]

The context could hold a security context which could be used to check permissions, e.g. restrict visibility of data.

[AlphonseSantoro]

You can access the context by using

type<Post>{
    property(Post::id){
        accessRule { post, ctx ->
            if(post.id == ctx.get<String>()) null else IllegalAccessException()
        }
    }
}

and

query("black_mamba") {
    resolver { -> Player("KOBE") }
    accessRule { ctx -> if (ctx.get<String>().equals("LAKERS")) null else IllegalAccessException() }
}

What I'm missing is that you can access the properties and context in the query itself.
e.g. I want a user to be able to read all posts but i dont want the user to edit posts of other users

[StefanLiebig]

Ah, ok - Thanks!

.. but i dont want the user to edit posts of other users

Is this about mutations?

[AlphonseSantoro]

Is this about mutations?

Both, it's about accessing properties in each query/mutation.
When using the first example I gave, the access rule applies to all queries/mutations to that type. As of now i can't see there is any property access on query/mutation level.

[StefanLiebig]

Ok, I got your point! I have not yet used mutations, so I did not stumble upon this problem.

This 'accessRule' looks nice, but it prevents my use case. I do not want to do the permission checking in the graphql layer but a little bit deeper in the 'data' layer because a parallel REST-API also uses this 'data' layer.

So I would like to have the possibility to pass the context (more precise: just the authorization part of it) to the 'data' layer. The suspendResolver/resolver function inside a query accepts a context object as parameter so that I can forward it:

    query("timeEntries") {
        suspendResolver { ctx: Context, year: Int?, month: Int?, userId: UserId?, topicFK: Int?, timeEntryTypeFK: Int? ->
            // forward "ctx" to the "data" layer.
        }
    }

Unfortunatlly, this is not possible with the property resolver.

[pgutkowski]

Hi @StefanHUB and @AlphonseSantoro

You can use Context in resolvers of queries, extension properties and transformations (I have to update the documentation), see:

KGraphQL/src/test/kotlin/com/github/pgutkowski/kgraphql/schema/SchemaBuilderTest.kt

Line 321 in 780eda8

fun `client code can use context class in property resolver`(){

But if I understand correctly, you would like to declare "resolver" for Kotlin properties as well, with access to property and context?

DSL example (not implemented yet):

type<Actor> {
                property(Actor::name) {
                    resolver { actor : Actor, ctx: Context ->
                        if(ctx.get<UserData>()?.canAccessActorName){
                            actor.name
                        } else {
                            throw UnauthorizedAccessException()
                        }
                    }
                }
}

Would this solve your use case?

[NataliiaVallander]

UPDATE: Working from locally built version. Probably last release is too old
@pgutkowski This works, but still there is a problem -- schema became invalid. I am getting this in qraphiql:
Error: Invalid or incomplete schema, unknown type: null. Ensure that a full introspection query is used in order to build a client schema.
As I understand this is because Context become input type which is not defined.
If I am trying to define it as Input Type am getting an error that generic classes are not supported from handleInputValues method.
Do you have any suggestions how to fix this?