Deriving query code from type

[CGenie]

Hello,

Suppose I have a type

newtype User = 
  { id :: Int
  , name  :: String
}

Is it possible to automatically create a "full" query for it? I.e I don't want to type

type UserGQL =
  { id :: Int
  , name :: String
  }

and then create a schema out of it, and then remap the UserGQL from the response but just directly define User in schema and have it automatically generate all fields for the query?

Just a note: my model is more complex, with complex types inside of it. On the Haskell side I'm able to derive the deeply nested models structure via the Morpheus library without hand-writing anything.

[roryc89]

@CGenie I can see the use of this but unfortunately this library does not support this yet.

This could probably be achieved outside of this library by defining your own type class that would deep map a record proxy (in this case User) and return a query record for it.

i.e.

class GetQueryFields r query | r -> query where 
   getQueryFields :: Proxy (Record r) -> query

The the instances could be defined using https://github.com/natefaubion/purescript-heterogeneous or some sort of generics.

The only part I'm not sure of is how to handle arguments on fields. Do you know how Morpheus handles this?

Is this something that you may work on? If so let please make a PR and I'll add it. If not, I'll probably be able to work on it soon.

I'll have a look at adding this today

[roryc89]

@CGenie I've added some functions that generate queries from types at https://github.com/OxfordAbstracts/purescript-graphql-client/pull/68/files . Is this the sort of thing you had in mind?

[CGenie]

For Morpheus you basically need to derive the GQLType class
https://hackage.haskell.org/package/morpheus-graphql-0.17.0/docs/Data-Morpheus-Types.html
and it works (i.e. the server-side is able to generate all the code to handle queries, that includes listing all of model's fields in the playground).

Thanks @roryc89 for that solution, looks interesting, I'll check out in more detail and will let you know.

[CGenie]

Is it possible to do a similar thing for newtype? (I guess sum types would be more difficult, does GraphQL support querying sum types at all?)

Then my question is https://github.com/OxfordAbstracts/purescript-graphql-client/pull/68/files#diff-404493334c4108c2411bd1767059be2e94295df5742d14d58116667dc5e80dd7R16-R19 really necessary, seems like duplication of the User type defined above.

[roryc89]

is https://github.com/OxfordAbstracts/purescript-graphql-client/pull/68/files#diff-404493334c4108c2411bd1767059be2e94295df5742d14d58116667dc5e80dd7R16-R19 really necessary, seems like duplication of the User type defined above.

No that's not necessary. It was just a type level test so I could check that getFieldsStandard returns the corrects query type. Going forward I would imagine adding a function that derived the query and ran it so that from the library user's point of view it could work similarly to morpheus, if you wanted.

For custom types, you could either derive the type class instance using derive newtype instance or create your instance if you wanted you a custom query with arguments, directives, aliases or anything else.

[roryc89]

I think that keeping the ability to run the queries without a type is also useful as sometimes I want to query a graphql api without having to write out the return type but still have it inferred

[roryc89]

(I guess sum types would be more difficult, does GraphQL support querying sum types at all?)

At the moment we generate the purescript sum type from graphql enums during codegen. You can see an example of this at https://github.com/OxfordAbstracts/purescript-graphql-client/blob/main/examples/3-enums/src/Main.purs