Add support for interfaces on interfaces

graphene/types/interface.py

@@ -5,11 +5,12 @@
 # For static type checking with Mypy
 MYPY = False
 if MYPY:
-    from typing import Dict  # NOQA
+    from typing import Dict, Iterable, Type  # NOQA
 
 
 class InterfaceOptions(BaseOptions):
     fields = None  # type: Dict[str, Field]
+    interfaces = ()  # type: Iterable[Type[Interface]]
 
 
 class Interface(BaseType):
@@ -45,7 +46,7 @@ class Meta:
     """
 
     @classmethod
-    def __init_subclass_with_meta__(cls, _meta=None, **options):
+    def __init_subclass_with_meta__(cls, _meta=None, interfaces=(), **options):
         if not _meta:
             _meta = InterfaceOptions(cls)
 
@@ -58,6 +59,9 @@ def __init_subclass_with_meta__(cls, _meta=None, **options):
         else:
             _meta.fields = fields
 
+        if not _meta.interfaces:
+            _meta.interfaces = interfaces
+
         super(Interface, cls).__init_subclass_with_meta__(_meta=_meta, **options)
 
     @classmethod

graphene/types/schema.py

@@ -236,11 +236,20 @@ def create_interface(self, graphene_type):
             else None
         )
 
+        def interfaces():
+            interfaces = []
+            for graphene_interface in graphene_type._meta.interfaces:
+                interface = self.add_type(graphene_interface)
+                assert interface.graphene_type == graphene_interface
+                interfaces.append(interface)
+            return interfaces
+
         return GrapheneInterfaceType(
             graphene_type=graphene_type,
             name=graphene_type._meta.name,
             description=graphene_type._meta.description,
             fields=partial(self.create_fields_for_type, graphene_type),
+            interfaces=interfaces,
             resolve_type=resolve_type,
         )
 

graphene/types/tests/test_interface.py

@@ -25,13 +25,18 @@ class MyInterface(Interface):
 
 
 def test_generate_interface_with_meta():
+    class MyFirstInterface(Interface):
+        pass
+
     class MyInterface(Interface):
         class Meta:
             name = "MyOtherInterface"
             description = "Documentation"
+            interfaces = [MyFirstInterface]
 
     assert MyInterface._meta.name == "MyOtherInterface"
     assert MyInterface._meta.description == "Documentation"
+    assert MyInterface._meta.interfaces == [MyFirstInterface]
 
 
 def test_generate_interface_with_fields():

graphene/types/tests/test_type_map.py

@@ -270,3 +270,33 @@ class Meta:
     assert graphql_type.is_type_of
     assert graphql_type.is_type_of({}, None) is True
     assert graphql_type.is_type_of(MyObjectType(), None) is False
+
+
+def test_interface_with_interfaces():
+    class FooInterface(Interface):
+        foo = String()
+
+    class BarInterface(Interface):
+        class Meta:
+            interfaces = [FooInterface]
+
+        foo = String()
+        bar = String()
+
+    type_map = create_type_map([FooInterface, BarInterface])
+    assert "FooInterface" in type_map
+    foo_graphql_type = type_map["FooInterface"]
+    assert isinstance(foo_graphql_type, GraphQLInterfaceType)
+    assert foo_graphql_type.name == "FooInterface"
+
+    assert "BarInterface" in type_map
+    bar_graphql_type = type_map["BarInterface"]
+    assert isinstance(bar_graphql_type, GraphQLInterfaceType)
+    assert bar_graphql_type.name == "BarInterface"
+
+    fields = bar_graphql_type.fields
+    assert list(fields) == ["foo", "bar"]
+    assert isinstance(fields["foo"], GraphQLField)
+    assert isinstance(fields["bar"], GraphQLField)
+
+    assert bar_graphql_type.interfaces == [foo_graphql_type]