Add support for interface implementing other interfaces (#1012)

* Add support in parser for interfaces implementing interfaces

* Walk interfaces on interfaces in AST

* Validate interface implementations on interfaces

* Add interfaces on interfaces support in macro schema

* Add interface info on interface type

* Add validation disallowing interface cycles

* Add no interface cycle validation to schema pipeline

* Test SDL interfaces

* Add interface implements to sdl render

* Improve tests for interfaces implementing interfaces

* Fix comment

lib/absinthe/blueprint/schema/interface_type_definition.ex

@@ -12,6 +12,8 @@ defmodule Absinthe.Blueprint.Schema.InterfaceTypeDefinition do
     description: nil,
     fields: [],
     directives: [],
+    interfaces: [],
+    interface_blueprints: [],
     source_location: nil,
     # Added by phases
     flags: %{},
@@ -27,6 +29,8 @@ defmodule Absinthe.Blueprint.Schema.InterfaceTypeDefinition do
           description: nil | String.t(),
           fields: [Blueprint.Schema.FieldDefinition.t()],
           directives: [Blueprint.Directive.t()],
+          interfaces: [String.t()],
+          interface_blueprints: [Blueprint.Draft.t()],
           source_location: nil | Blueprint.SourceLocation.t(),
           # Added by phases
           flags: Blueprint.flags_t(),
@@ -40,12 +44,15 @@ defmodule Absinthe.Blueprint.Schema.InterfaceTypeDefinition do
       fields: Blueprint.Schema.ObjectTypeDefinition.build_fields(type_def, schema),
       identifier: type_def.identifier,
       resolve_type: type_def.resolve_type,
-      definition: type_def.module
+      definition: type_def.module,
+      interfaces: type_def.interfaces
     }
   end
 
+  @interface_types [Schema.ObjectTypeDefinition, Schema.InterfaceTypeDefinition]
+
   def find_implementors(iface, type_defs) do
-    for %Schema.ObjectTypeDefinition{} = obj <- type_defs,
+    for %struct{} = obj when struct in @interface_types <- type_defs,
         iface.identifier in obj.interfaces,
         do: obj.identifier
   end

lib/absinthe/blueprint/transform.ex

@@ -83,7 +83,7 @@ defmodule Absinthe.Blueprint.Transform do
     Blueprint.Schema.FieldDefinition => [:type, :arguments, :directives],
     Blueprint.Schema.InputObjectTypeDefinition => [:fields, :directives],
     Blueprint.Schema.InputValueDefinition => [:type, :default_value, :directives],
-    Blueprint.Schema.InterfaceTypeDefinition => [:fields, :directives],
+    Blueprint.Schema.InterfaceTypeDefinition => [:interfaces, :fields, :directives],
     Blueprint.Schema.ObjectTypeDefinition => [:interfaces, :fields, :directives],
     Blueprint.Schema.ScalarTypeDefinition => [:directives],
     Blueprint.Schema.SchemaDefinition => [:directive_definitions, :type_definitions, :directives],

lib/absinthe/language/interface_type_definition.ex

@@ -7,13 +7,15 @@ defmodule Absinthe.Language.InterfaceTypeDefinition do
             description: nil,
             fields: [],
             directives: [],
+            interfaces: [],
             loc: %{line: nil}
 
   @type t :: %__MODULE__{
           name: String.t(),
           description: nil | String.t(),
           fields: [Language.FieldDefinition.t()],
           directives: [Language.Directive.t()],
+          interfaces: [Language.NamedType.t()],
           loc: Language.loc_t()
         }
 
@@ -25,10 +27,18 @@ defmodule Absinthe.Language.InterfaceTypeDefinition do
         identifier: Macro.underscore(node.name) |> String.to_atom(),
         fields: Absinthe.Blueprint.Draft.convert(node.fields, doc),
         directives: Absinthe.Blueprint.Draft.convert(node.directives, doc),
+        interfaces: interfaces(node.interfaces, doc),
+        interface_blueprints: Absinthe.Blueprint.Draft.convert(node.interfaces, doc),
         source_location: source_location(node)
       }
     end
 
+    defp interfaces(interfaces, doc) do
+      interfaces
+      |> Absinthe.Blueprint.Draft.convert(doc)
+      |> Enum.map(&(&1.name |> Macro.underscore() |> String.to_atom()))
+    end
+
     defp source_location(%{loc: nil}), do: nil
     defp source_location(%{loc: loc}), do: Blueprint.SourceLocation.at(loc)
   end

lib/absinthe/phase/schema/validation/no_interface_cycles.ex

@@ -0,0 +1,78 @@
+defmodule Absinthe.Phase.Schema.Validation.NoInterfaceCyles do
+  @moduledoc false
+
+  use Absinthe.Phase
+  alias Absinthe.Blueprint
+  alias Absinthe.Blueprint.Schema
+
+  def run(blueprint, _opts) do
+    blueprint = check(blueprint)
+
+    {:ok, blueprint}
+  end
+
+  defp check(blueprint) do
+    graph = :digraph.new([:cyclic])
+
+    try do
+      _ = build_interface_graph(blueprint, graph)
+
+      Blueprint.prewalk(blueprint, &validate_schema(&1, graph))
+    after
+      :digraph.delete(graph)
+    end
+  end
+
+  defp validate_schema(%Schema.InterfaceTypeDefinition{} = interface, graph) do
+    if cycle = :digraph.get_cycle(graph, interface.identifier) do
+      interface |> put_error(error(interface, cycle))
+    else
+      interface
+    end
+  end
+
+  defp validate_schema(node, _graph) do
+    node
+  end
+
+  defp build_interface_graph(blueprint, graph) do
+    _ = Blueprint.prewalk(blueprint, &vertex(&1, graph))
+  end
+
+  defp vertex(%Schema.InterfaceTypeDefinition{} = implementor, graph) do
+    :digraph.add_vertex(graph, implementor.identifier)
+
+    for interface <- implementor.interfaces do
+      edge(implementor, interface, graph)
+    end
+
+    implementor
+  end
+
+  defp vertex(implementor, _graph) do
+    implementor
+  end
+
+  # Add an edge, modeling the relationship between two interfaces
+  defp edge(implementor, interface, graph) do
+    :digraph.add_vertex(graph, interface)
+
+    :digraph.add_edge(graph, implementor.identifier, interface)
+
+    true
+  end
+
+  defp error(type, deps) do
+    %Absinthe.Phase.Error{
+      message:
+        String.trim("""
+        Interface Cycle Error
+
+        Interface `#{type.identifier}' forms a cycle via: (#{inspect(deps)})
+        """),
+      locations: [type.__reference__.location],
+      phase: __MODULE__,
+      extra: type.identifier
+    }
+  end
+end

lib/absinthe/phase/schema/validation/object_must_implement_interfaces.ex

@@ -25,7 +25,12 @@ defmodule Absinthe.Phase.Schema.Validation.ObjectMustImplementInterfaces do
     obj
   end
 
-  defp validate_objects(%Blueprint.Schema.ObjectTypeDefinition{} = object, ifaces, types) do
+  @interface_types [
+    Blueprint.Schema.ObjectTypeDefinition,
+    Blueprint.Schema.InterfaceTypeDefinition
+  ]
+
+  defp validate_objects(%struct{} = object, ifaces, types) when struct in @interface_types do
     Enum.reduce(object.interfaces, object, fn ident, object ->
       case Map.fetch(ifaces, ident) do
         {:ok, iface} -> validate_object(object, iface, types)

lib/absinthe/pipeline.ex

@@ -150,6 +150,7 @@ defmodule Absinthe.Pipeline do
       Phase.Schema.Validation.InterfacesMustResolveTypes,
       Phase.Schema.Validation.ObjectInterfacesMustBeValid,
       Phase.Schema.Validation.ObjectMustImplementInterfaces,
+      Phase.Schema.Validation.NoInterfaceCyles,
       Phase.Schema.Validation.QueryTypeMustBeObject,
       Phase.Schema.Validation.NamesMustBeValid,
       Phase.Schema.RegisterTriggers,

lib/absinthe/schema/notation.ex

@@ -220,7 +220,7 @@ defmodule Absinthe.Schema.Notation do
     )
   end
 
-  @placement {:interfaces, [under: [:object]]}
+  @placement {:interfaces, [under: [:object, :interface]]}
   @doc """
   Declare implemented interfaces for an object.
 
@@ -299,7 +299,7 @@ defmodule Absinthe.Schema.Notation do
   end
   ```
   """
-  @placement {:interface_attribute, [under: [:object]]}
+  @placement {:interface_attribute, [under: [:object, :interface]]}
   defmacro interface(identifier) do
     __CALLER__
     |> recordable!(:interface_attribute, @placement[:interface_attribute])

lib/absinthe/schema/notation/sdl_render.ex

@@ -173,6 +173,7 @@ defmodule Absinthe.Schema.Notation.SDL.Render do
       "interface",
       concat([
         string(interface_type.name),
+        implements(interface_type, type_definitions),
         directives(interface_type.directives, type_definitions)
       ]),
       render_list(interface_type.fields, type_definitions)

lib/absinthe/type/interface.ex

@@ -63,6 +63,7 @@ defmodule Absinthe.Type.Interface do
           description: binary,
           fields: map,
           identifier: atom,
+          interfaces: [Absinthe.Type.Interface.t()],
           __private__: Keyword.t(),
           definition: module,
           __reference__: Type.Reference.t()
@@ -73,6 +74,7 @@ defmodule Absinthe.Type.Interface do
             fields: nil,
             identifier: nil,
             resolve_type: nil,
+            interfaces: [],
             __private__: [],
             definition: nil,
             __reference__: nil

src/absinthe_parser.yrl

@@ -261,6 +261,11 @@ InterfaceTypeDefinition -> 'interface' Name '{' FieldDefinitionList '}' :
   build_ast_node('InterfaceTypeDefinition', #{'name' => extract_binary('$2'), 'fields' => '$4'}, extract_location('$1')).
 InterfaceTypeDefinition -> 'interface' Name Directives '{' FieldDefinitionList '}' :
   build_ast_node('InterfaceTypeDefinition', #{'name' => extract_binary('$2'), 'directives' => '$3', 'fields' => '$5'}, extract_location('$1')).
+InterfaceTypeDefinition -> 'interface' Name ImplementsInterfaces '{' FieldDefinitionList '}' :
+  build_ast_node('InterfaceTypeDefinition', #{'name' => extract_binary('$2'), 'interfaces' => '$3', 'fields' => '$5'}, extract_location('$1')).
+InterfaceTypeDefinition -> 'interface' Name ImplementsInterfaces Directives '{' FieldDefinitionList '}' :
+  build_ast_node('InterfaceTypeDefinition', #{'name' => extract_binary('$2'), 'interfaces' => '$3', 'directives' => '$4', 'fields' => '$6'}, extract_location('$1')).
+
 
 UnionTypeDefinition -> 'union' Name :
   build_ast_node('UnionTypeDefinition', #{'name' => extract_binary('$2')}, extract_location('$1')).

test/absinthe/schema/notation_test.exs

@@ -204,14 +204,14 @@ defmodule Absinthe.Schema.NotationTest do
           interface :foo
         end
         """,
-        "Invalid schema notation: `interface_attribute` must only be used within `object`"
+        "Invalid schema notation: `interface_attribute` must only be used within `object`, `interface`"
       )
     end
   end
 
   describe "interfaces" do
     test "can be under object as an attribute" do
-      assert_no_notation_error("InterfacesValid", """
+      assert_no_notation_error("ObjectInterfacesValid", """
       interface :bar do
         field :name, :string
         resolve_type fn _, _ -> :foo end
@@ -223,6 +223,19 @@ defmodule Absinthe.Schema.NotationTest do
       """)
     end
 
+    test "can be under interface as an attribute" do
+      assert_no_notation_error("InterfaceInterfacesValid", """
+      interface :bar do
+        field :name, :string
+        resolve_type fn _, _ -> :foo end
+      end
+      interface :foo do
+        field :name, :string
+        interfaces [:bar]
+      end
+      """)
+    end
+
     test "cannot be toplevel" do
       assert_notation_error(
         "InterfacesInvalid",
@@ -232,7 +245,7 @@ defmodule Absinthe.Schema.NotationTest do
         end
         interfaces [:bar]
         """,
-        "Invalid schema notation: `interfaces` must only be used within `object`"
+        "Invalid schema notation: `interfaces` must only be used within `object`, `interface`"
       )
     end
   end

test/absinthe/schema/rule/no_interface_cycles_test.exs

@@ -0,0 +1,36 @@
+defmodule Absinthe.Schema.Rule.NoInterfacecyclesTest do
+  use Absinthe.Case, async: true
+
+  describe "rule" do
+    test "is enforced" do
+      assert_schema_error("interface_cycle_schema", [
+        %{
+          extra: :named,
+          locations: [
+            %{
+              file: "test/support/fixtures/dynamic/interface_cycle_schema.exs",
+              line: 24
+            }
+          ],
+          message:
+            "Interface Cycle Error\n\nInterface `named' forms a cycle via: ([:named, :node, :named])",
+          path: [],
+          phase: Absinthe.Phase.Schema.Validation.NoInterfaceCyles
+        },
+        %{
+          extra: :node,
+          locations: [
+            %{
+              file: "test/support/fixtures/dynamic/interface_cycle_schema.exs",
+              line: 24
+            }
+          ],
+          message:
+            "Interface Cycle Error\n\nInterface `node' forms a cycle via: ([:node, :named, :node])",
+          path: [],
+          phase: Absinthe.Phase.Schema.Validation.NoInterfaceCyles
+        }
+      ])
+    end
+  end
+end

test/absinthe/schema/rule/object_must_implement_interfaces_test.exs

@@ -19,7 +19,13 @@ defmodule Absinthe.Schema.Rule.ObjectMustImplementInterfacesTest do
     use Absinthe.Schema
     import_types Types
 
+    interface :parented do
+      field :parent, :named
+      field :another_parent, :named
+    end
+
     interface :named do
+      interface :parented
       field :name, :string
       field :parent, :named
       field :another_parent, :named
@@ -80,10 +86,48 @@ defmodule Absinthe.Schema.Rule.ObjectMustImplementInterfacesTest do
   end
 
   test "interfaces are propogated across type imports" do
-    assert %{named: [:cat, :dog, :user], favorite_foods: [:cat, :dog, :user]} ==
+    assert %{
+             named: [:cat, :dog, :user],
+             favorite_foods: [:cat, :dog, :user],
+             parented: [:named]
+           } ==
              Schema.__absinthe_interface_implementors__()
   end
 
+  defmodule InterfaceImplementsInterfaces do
+    use Absinthe.Schema
+
+    import_sdl """
+    interface Node {
+      id: ID!
+    }
+
+    interface Resource implements Node {
+      id: ID!
+      url: String
+    }
+
+    interface Image implements Resource & Node {
+      id: ID!
+      url: String
+      thumbnail: String
+    }
+
+    """
+
+    query do
+    end
+  end
+
+  test "interfaces are set from sdl" do
+    assert %{
+             image: [],
+             node: [:image, :resource],
+             resource: [:image]
+           } ==
+             InterfaceImplementsInterfaces.__absinthe_interface_implementors__()
+  end
+
   test "is enforced" do
     assert_schema_error("invalid_interface_types", [
       %{