Change gen usage

[ghostdogpr]

TL;DR
gen[A] becomes gen[R, A]

For Scala 2:
You no longer need to worry about calling the right gen (from Schema vs GenericSchema), you can simply use Schema.gen everywhere. It now takes 2 type parameters R and A but you can usually omit them if you explicitly define the return type of your schema.

object schema extends GenericSchema[MyEnv]
import schema._

implicit val queriesSchema: Schema[MyEnv, Queries] = Schema.gen
// or
implicit val queriesSchema = Schema.gen[MyEnv, Queries]

If you use genMacro, you still need to do it on GenericSchema.

For Scala 3:
It is no longer necessary to use GenericSchema[R]. You can simply use Schema.gen when you need to explicitly derive a schema. Caliban will be able to derive a Schema[R, A] directly from that.

If your R is not Any, you need to pass it to the graphQL function, unless you already have a Schema[R, Query] in scope:

val api = graphQL[MyEnv, Queries, Unit, Unit](RootResolver(queries))
// or
implicit val queriesSchema: Schema[MyEnv, Queries] = Schema.gen
val api = graphQL(RootResolver(queries))

If you want to see the code generated by the derivation, you can use Schema.genDebug instead. It will print the generated code to the console when compiling.