Parsing an SDL file with extend schema leads to NoMethodError (name on GraphQL::Language::Nodes::SchemaExtension)

[myronmarston]

Describe the bug

Apollo requires the following in a subgraph schema for Apollo Federation V2:

extend schema
  @link(url: "https://specs.apollo.dev/federation/v2.0",
        import: ["@key", "@shareable"])

However, when I try to parse an SDL file that contains this using graphql-ruby, I get a NoMethodError

Versions

graphql version: 2.0.14

GraphQL schema

See the script below for a full runnable example of this bug.

GraphQL query

N/A

Steps to reproduce

Put this file in tmp/graphql_ruby_bug.rb:

require "bundler/inline"

gemfile do
  source "https://rubygems.org"
  gem "graphql", "2.0.14"
end

schema_sdl = <<~EOS
  extend schema
    @link(url: "https://specs.apollo.dev/federation/v2.0",
          import: ["@key", "@shareable"])

  type Query {
    something: Int
  }
EOS

require "graphql"

GraphQL::Schema.from_definition(schema_sdl)

Then run with:

$ ruby tmp/graphql_ruby_bug.rb

Expected behavior

This SDL string should parse without throwing any exceptions.

Actual behavior

$ ruby tmp/graphql_ruby_bug.rb                                                                                                                                                                                                                                                                        Traceback (most recent call last):
        6: from tmp/graphql_ruby_bug.rb:20:in `<main>'
        5: from /Users/myron/.rvm/gems/ruby-2.7.5/gems/graphql-2.0.14/lib/graphql/schema.rb:122:in `from_definition'
        4: from /Users/myron/.rvm/gems/ruby-2.7.5/gems/graphql-2.0.14/lib/graphql/schema/build_from_definition.rb:10:in `from_definition'
        3: from /Users/myron/.rvm/gems/ruby-2.7.5/gems/graphql-2.0.14/lib/graphql/schema/build_from_definition.rb:18:in `from_document'
        2: from /Users/myron/.rvm/gems/ruby-2.7.5/gems/graphql-2.0.14/lib/graphql/schema/build_from_definition.rb:68:in `build'
        1: from /Users/myron/.rvm/gems/ruby-2.7.5/gems/graphql-2.0.14/lib/graphql/schema/build_from_definition.rb:68:in `each'
/Users/myron/.rvm/gems/ruby-2.7.5/gems/graphql-2.0.14/lib/graphql/schema/build_from_definition.rb:74:in `block in build': 
undefined method `name' for #<GraphQL::Language::Nodes::SchemaExtension:0x0000000130a2b580> (NoMethodError)

Additional context

It looks like the case statement clause here is missing GraphQL::Language::Nodes::SchemaExtension.

https://github.com/rmosolgo/graphql-ruby/blob/v2.0.14/lib/graphql/schema/build_from_definition.rb#L70

If I add GraphQL::Language::Nodes::SchemaExtension to it, I no longer get the exception.

[rmosolgo]

Thanks for the detailed report! I think we updated the parser to handle extensions but never actually implemented loading schemas with extend. But I can take a look at getting that started 👍

[rmosolgo]

I'm taking a look over at #4203.

One issue is, GraphQL-Ruby can't validate extend schema @link(...) usage without a directive @link(...) definition in the document. Would it be reasonable to include a directive @link ... definition, as described in https://www.apollographql.com/docs/federation/federated-types/federated-directives/#link ?

Alternatively, you could lay out the directive definition in the schema class, then call .from_definition on that custom class, as demonstrated in this example:

graphql-ruby/spec/graphql/schema/build_from_definition_spec.rb

Lines 1615 to 1636 in fd8f468

	class LinkSchema < GraphQL::Schema
	class Import < GraphQL::Schema::Scalar
	end
	class Purpose < GraphQL::Schema::Scalar
	end
	class Link < GraphQL::Schema::Directive
	argument :url, String
	argument :as, String, required: false
	argument :import, Import, required: false
	argument :for, Purpose, required: false
	repeatable(true)
	locations SCHEMA
	end
	directive(Link)
	end
	assert_equal LinkSchema::Link, LinkSchema.directives["link"]
	schema = LinkSchema.from_definition(schema_sdl)

Would one of those approaches work for your use case?

[myronmarston]

Great catch! You're right that my SDL is missing a definition for the @link directive. I don't expect the graphql gem to magically understand it, and in fact in my real SDL file I have this definition for it:

scalar link__Import
directive @link(import: [link__Import], url: String!) on SCHEMA

On a side note: I didn't realize you could define some parts of a schema in ruby, and load a definition for the rest into it--that's cool and I may use that in the future--so thanks!

[rmosolgo]

define some parts of a schema in ruby

To clarify, it's actually leveraging inheritance: the directive is added to the superclass, then .from_definition(...) creates a subclass. But that won't work properly until #4203 is merged 😅