Implement schema loading from adapter

lib/graphql/client.rb

@@ -21,6 +21,8 @@ module GraphQL
 
     attr_accessor :document_tracking_enabled
 
+    IntrospectionDocument = GraphQL.parse(GraphQL::Introspection::INTROSPECTION_QUERY).deep_freeze
+
     def self.load_schema(schema)
       case schema
       when GraphQL::Schema
@@ -33,6 +35,17 @@ module GraphQL
         else
           load_schema(JSON.parse(schema))
         end
+      else
+        if schema.respond_to?(:execute)
+          load_schema(
+            schema.execute(
+              document: IntrospectionDocument,
+              operation_name: "IntrospectionQuery",
+              variables: {},
+              context: {}
+            )
+          )
+        end
       end
     end
 
@@ -236,17 +249,6 @@ module GraphQL
       Response.for(definition, result)
     end
 
-    IntrospectionDocument = GraphQL.parse(GraphQL::Introspection::INTROSPECTION_QUERY).deep_freeze
-
-    def fetch_schema
-      execute.execute(
-        document: IntrospectionDocument,
-        operation_name: "IntrospectionQuery",
-        variables: {},
-        context: {}
-      )
-    end
-
     # Internal: FragmentSpread and FragmentDefinition extension to allow its
     # name to point to a lazily defined Proc instead of a static string.
     module LazyName

test/test_client_schema.rb

@@ -0,0 +1,30 @@
+require "graphql"
+require "graphql/client"
+require "json"
+require "minitest/autorun"
+
+class TestClientSchema < MiniTest::Test
+  QueryType = GraphQL::ObjectType.define do
+    name "AwesomeQuery"
+    field :version, !types.Int
+  end
+
+  Schema = GraphQL::Schema.define(query: QueryType)
+
+  def test_load_schema_identity
+    schema = GraphQL::Client.load_schema(Schema)
+    assert_equal "AwesomeQuery", schema.query.name
+  end
+
+  def test_load_schema_from_introspection_query_result
+    result = Schema.execute(GraphQL::Introspection::INTROSPECTION_QUERY)
+    schema = GraphQL::Client.load_schema(result)
+    assert_equal "AwesomeQuery", schema.query.name
+  end
+
+  def test_load_schema_from_json_string
+    json = JSON.generate(Schema.execute(GraphQL::Introspection::INTROSPECTION_QUERY))
+    schema = GraphQL::Client.load_schema(json)
+    assert_equal "AwesomeQuery", schema.query.name
+  end
+end