Add supports for Type extention ("extend type" syntax)

[takeyoda]

What

Add supports for Type extention ("extend type" syntax)

Why

In GraphQL, we can extend a type using the "extend type" syntax, like the following example:

type Item {
  title: String!
}
extend type Item { # HERE
  price: Int!
}
type Query {
  item: Item
}

Type "Item" contains two attributes "title" and "price".
When generating a GraphQL query with graphql-autotest from the above schema,
the "price" attribute is not output.

In GraphQL-Ruby, an "extend type" block is treated as an independent instance of ObjectTypeExtension class.
It means that multiple definitions with the same name are included in Document#definitions.
On the other hand, QueryGenerator#type_definition assumes that there is only one definition that matches the name, so the definition inside the "extend type" block is not considered.

• Example

  require 'graphql'
  
  schema = <<~SCHEMA
    type Item {
      title: String!
    }
    extend type Item {
      price: Int!
    }
    type Query {
      item: Item!
    }
  SCHEMA
  
  doc = GraphQL::parse(schema)
  doc.definitions.map do |d|
    puts "name=#{d.name} (#{d.class})"
  end

  • Output

  name=Item (GraphQL::Language::Nodes::ObjectTypeDefinition)
  name=Item (GraphQL::Language::Nodes::ObjectTypeExtension)     # contains same named Node
  name=Query (GraphQL::Language::Nodes::ObjectTypeDefinition)
  

How to fix

Changed QueryGenerator#type_definition to merge all definitions that matched name.

⚠️ Note ⚠️

This change made graphql-autotest work as I expected, but I'm not sure it's the correct change.
For example, I'm worried about the following case expression:

graphql-autotest/lib/graphql/autotest/query_generator.rb

Lines 50 to 69 in d1d534d

	case field_type_def
	when nil, GraphQL::Language::Nodes::EnumTypeDefinition, GraphQL::Language::Nodes::ScalarTypeDefinition
	Field.new(name: f.name, children: nil, arguments: arguments)
	when GraphQL::Language::Nodes::UnionTypeDefinition
	possible_types = field_type_def.types.map do |t|
	t_def = type_definition(t.name)
	children = testable_fields(t_def, called_fields: called_fields.dup, depth: depth + 1, ancestors: [f, *ancestors])
	Field.new(name: "... on #{t.name}", children: children)
	end
	Field.new(name: f.name, children: possible_types + [Field::TYPE_NAME], arguments: arguments)
	else
	children = testable_fields(field_type_def, called_fields: called_fields.dup, depth: depth + 1, ancestors: [f, *ancestors])
	Field.new(
	name: f.name,
	children: children,
	arguments: arguments,
	)
	end
	end.compact + [Field::TYPE_NAME]

--
takeyoda

[kuroponzu]

@takeyoda
Sorry, please resolve conflicts 🙏