Don't return other interfaces in list of .possible_types

lib/graphql/schema/addition.rb

@@ -258,7 +258,9 @@ def add_type(type, owner:, late_types:, path:)
                 # We can get these now; we'll have to get late-bound types later
                 if interface_type.is_a?(Module) && type.is_a?(Class)
                   implementers = @possible_types[interface_type] ||= []
-                  implementers << type
+                  if !implementers.include?(type)
+                    implementers << type
+                  end
                 end
               when String, Schema::LateBoundType
                 interface_type = interface_type_membership

lib/graphql/schema/visibility.rb

@@ -212,7 +212,11 @@ def ensure_all_loaded(types_to_visit)
       def load_all(types: nil)
         if @visit.nil?
           # Set up the visit system
-          @interface_type_memberships = Hash.new { |h, interface_type| h[interface_type] = [] }.compare_by_identity
+          @interface_type_memberships = Hash.new { |h, interface_type|
+            h[interface_type] = Hash.new { |h2, obj_type|
+              h2[obj_type] = []
+            }.compare_by_identity
+          }.compare_by_identity
           @directives = []
           @types = {} # String => Module
           @all_references = Hash.new { |h, member| h[member] = Set.new.compare_by_identity }.compare_by_identity
@@ -237,7 +241,7 @@ def load_all(types: nil)
                   @all_references[itm.abstract_type] << member
                   # `itm.object_type` may not actually be `member` if this implementation
                   # is inherited from a superclass
-                  @interface_type_memberships[itm.abstract_type] << [itm, member]
+                  @interface_type_memberships[itm.abstract_type][member] << itm
                 end
               elsif member < GraphQL::Schema::Union
                 @unions_for_references << member
@@ -286,12 +290,11 @@ def load_all(types: nil)
 
         # TODO: somehow don't iterate over all these,
         # only the ones that may have been modified
-        @interface_type_memberships.each do |int_type, type_membership_pairs|
-          referers = @all_references[int_type].select { |r| r.is_a?(GraphQL::Schema::Field) }
-          if !referers.empty?
-            type_membership_pairs.each do |(type_membership, impl_type)|
-              # Add new items only:
-              @all_references[impl_type] |= referers
+        @interface_type_memberships.each do |int_type, obj_type_memberships|
+          referrers = @all_references[int_type].select { |r| r.is_a?(GraphQL::Schema::Field) }
+          if !referrers.empty?
+            obj_type_memberships.each_key do |impl_type|
+              @all_references[impl_type] |= referrers
             end
           end
         end

lib/graphql/schema/visibility/profile.rb

@@ -403,9 +403,11 @@ def possible_types_for(type)
           case type.kind.name
           when "INTERFACE"
             pts = []
-            @visibility.all_interface_type_memberships[type].each do |(itm, impl_type)|
-              if @cached_visible[itm] && @cached_visible[impl_type] && referenced?(impl_type)
-                pts << impl_type
+            @visibility.all_interface_type_memberships[type].each do |impl_type, type_memberships|
+              if impl_type.kind.object? && referenced?(impl_type) && @cached_visible[impl_type]
+                if type_memberships.any? { |itm| @cached_visible[itm] }
+                  pts << impl_type
+                end
               end
             end
             pts

spec/graphql/schema/interface_spec.rb

@@ -359,6 +359,11 @@ def thing
 
       assert_equal ["Named", "Node", "Timestamped"], interfaces_names
     end
+
+    it "doesn't return interfaces as possible types" do
+      pts = TransitiveInterfaceSchema.possible_types(TransitiveInterfaceSchema::Node)
+      assert_equal ["Thing"], pts.map(&:graphql_name)
+    end
   end
 
   describe "supplying a fallback_value to a field" do