Add debug info to UnresolvedTypeError

lib/graphql/unresolved_type_error.rb

@@ -24,11 +24,27 @@ def initialize(value, field, parent_type, resolved_type, possible_types)
       @parent_type = parent_type
       @resolved_type = resolved_type
       @possible_types = possible_types
-      message = "The value from \"#{field.graphql_name}\" on \"#{parent_type.graphql_name}\" could not be resolved to \"#{field.type.to_type_signature}\". " \
-        "(Received: `#{resolved_type.inspect}`, Expected: [#{possible_types.map(&:graphql_name).join(", ")}]) " \
-        "Make sure you have defined a `resolve_type` proc on your schema and that value `#{value.inspect}` " \
+      abstract_type = field.type.unwrap
+      message = "The value from \"#{field.graphql_name}\" on \"#{parent_type.graphql_name}\" could not be resolved to \"#{abstract_type.to_type_signature}\". " \
+        "(Received: `#{resolved_type.name ? resolved_type.inspect : resolved_type.graphql_name}`, Expected: [#{possible_types.map(&:graphql_name).join(", ")}]) " \
+        "Make sure you have defined a `resolve_type` method on your schema and that value `#{value.inspect}` " \
         "gets resolved to a valid type. You may need to add your type to `orphan_types` if it implements an " \
         "interface but isn't a return type of any other field."
+
+      if abstract_type.kind.interface? && (multiplex = Fiber[:__graphql_current_multiplex])
+        types = multiplex.queries.first.types # rubocop:disable Development/ContextIsPassedCop
+        if types.is_a?(Schema::Visibility::Profile)
+          message = message.dup
+          visibility = types.instance_variable_get(:@visibility)
+          cached_vis = types.instance_variable_get(:@cached_visible)
+          message << "\n\n`#{abstract_type.graphql_name}.orphan_types`: #{abstract_type.orphan_types}"
+          impls = visibility.all_interface_type_memberships[abstract_type]
+          message << "\n`Schema.visibility.all_interface_type_memberships[#{abstract_type.graphql_name}]` (#{impls.size}):"
+          impls.each do |(impl_type, memberships)|
+            message << "\n    - `#{impl_type.graphql_name}` | Object? #{impl_type.kind.object?} | referenced? #{types.send(:referenced?, impl_type)} | visible? #{cached_vis[impl_type]} | membership_visible? #{memberships.map { |itm| cached_vis[itm]}}"
+          end
+        end
+      end
       super(message)
     end
   end

spec/graphql/schema/member/has_unresolved_type_error_spec.rb

@@ -37,7 +37,7 @@
 
     schema = Class.new(GraphQL::Schema) do
       query(query_type)
-
+      use GraphQL::Schema::Visibility
       def self.resolve_type(abs_t, obj, ctx)
         ctx.schema.query
       end
@@ -52,5 +52,12 @@ def self.resolve_type(abs_t, obj, ctx)
       schema.execute("{ anonInt { __typename } }")
     end
     assert_equal "GraphQL::UnresolvedTypeError", err.class.name
+    assert_equal <<~ERR.chomp, err.message
+    The value from "anonInt" on "Query" could not be resolved to "AnonInt". (Received: `Query`, Expected: [Obj]) Make sure you have defined a `resolve_type` method on your schema and that value `1` gets resolved to a valid type. You may need to add your type to `orphan_types` if it implements an interface but isn\'t a return type of any other field.
+
+    `AnonInt.orphan_types`: []
+    `Schema.visibility.all_interface_type_memberships[AnonInt]` (1):
+        - `Obj` | Object? true | referenced? true | visible? true | membership_visible? [true]
+    ERR
   end
 end