Accept blocks to reference schema root types

[rmosolgo]

With this, the schema could defer loading a root type until necessary (thus also deferring loading all types referenced by it, resolvers, etc).

In this implementation, calling schema.query returns the deferred definition which means that if, say, a plug-in references that root type, all the magic is lost.

To be really effective, we'd also need some plugin behavior like extend(:query) { ... } where callbacks could be registered by the plugin, then called by GraphQL-Ruby after the type is actually loaded. I think that can be added later.

Part of #5014

TODO:

• Add a test that proves that Rails doesn't load types/query.rb until a query is run when using Schema::Subset.
• Write a Rubocop rule for it

[rmosolgo]

I confirmed this has the desired effect by making a Rails app and configuring the schema with:

puts ">>>> loading #{__FILE__}"

class GraphqlLazyLoadTestSchema < GraphQL::Schema
  self.use_schema_subset = true

  mutation { Types::MutationType }
  query { Types::QueryType }
  # ...
end 

Then, I ran two queries, and watched the Rails server logs:

query {
  __typename
}
# Processing by GraphqlController#execute as */*
#   Parameters: {"query"=>"query {\n  __typename\n}", "graphql"=>{"query"=>"query {\n  __typename\n}"}}
# >>>> loading /Users/rmosolgo/code/graphql_lazy_load_test/app/graphql/graphql_lazy_load_test_schema.rb
# >>>> loading /Users/rmosolgo/code/graphql_lazy_load_test/app/graphql/types/query_type.rb
# Completed 200 OK in 15ms (Views: 0.2ms | ActiveRecord: 0.0ms | Allocations: 6307)

Then:

mutation {
  __typename
}
# Started POST "/graphql" for 127.0.0.1 at 2024-08-08 10:57:45 -0400
# Processing by GraphqlController#execute as */*
#   Parameters: {"query"=>"mutation {\n  __typename\n}", "graphql"=>{"query"=>"mutation {\n  __typename\n}"}}
# >>>> loading /Users/rmosolgo/code/graphql_lazy_load_test/app/graphql/types/mutation_type.rb
# Completed 200 OK in 3ms (Views: 0.1ms | ActiveRecord: 0.0ms | Allocations: 1025)

So, it works: running a query doesn't cause types/mutation.rb to be loaded 🎉