From b1184fe590be795412e234078c7ba2d61326e800 Mon Sep 17 00:00:00 2001
From: Thomas Marshall <thomas@thomasmarshall.com>
Date: Sun, 7 Apr 2024 04:53:08 +0100
Subject: [PATCH] Fix hydration of boundaries with abstract types (#130)

---
 lib/graphql/stitching/supergraph.rb                |  3 ++-
 .../stitching/supergraph/resolver_directive.rb     |  1 +
 test/graphql/stitching/supergraph_test.rb          | 14 +++++++++-----
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/lib/graphql/stitching/supergraph.rb b/lib/graphql/stitching/supergraph.rb
index 88247841..aa3c70d5 100644
--- a/lib/graphql/stitching/supergraph.rb
+++ b/lib/graphql/stitching/supergraph.rb
@@ -31,7 +31,7 @@ def from_definition(schema, executables:)
               kwargs = directive.arguments.keyword_arguments
               boundary_map[type_name] ||= []
               boundary_map[type_name] << Boundary.new(
-                type_name: type_name,
+                type_name: kwargs.fetch(:type_name, type_name),
                 location: kwargs[:location],
                 key: kwargs[:key],
                 field: kwargs[:field],
@@ -134,6 +134,7 @@ def to_definition
               end
 
               type.directive(ResolverDirective, **{
+                type_name: (boundary.type_name if boundary.type_name != type_name),
                 location: boundary.location,
                 key: boundary.key,
                 field: boundary.field,
diff --git a/lib/graphql/stitching/supergraph/resolver_directive.rb b/lib/graphql/stitching/supergraph/resolver_directive.rb
index eeaa9501..4214325b 100644
--- a/lib/graphql/stitching/supergraph/resolver_directive.rb
+++ b/lib/graphql/stitching/supergraph/resolver_directive.rb
@@ -5,6 +5,7 @@ class Supergraph
     class ResolverDirective < GraphQL::Schema::Directive
       graphql_name "resolver"
       locations OBJECT, INTERFACE, UNION
+      argument :type_name, String, required: false
       argument :location, String, required: true
       argument :key, String, required: true
       argument :field, String, required: true
diff --git a/test/graphql/stitching/supergraph_test.rb b/test/graphql/stitching/supergraph_test.rb
index dde7a45b..f0bf0777 100644
--- a/test/graphql/stitching/supergraph_test.rb
+++ b/test/graphql/stitching/supergraph_test.rb
@@ -314,8 +314,9 @@ def test_route_type_to_locations_returns_nil_for_unreachable_locations
   describe "#to_definition / #from_definition" do
     def setup
       alpha = %|
-        type T { id:ID! a:String }
-        type Query { a(id:ID!):T @stitch(key: "id") }
+        type T implements A { id:ID! a:String }
+        interface A { id:ID! }
+        type Query { a(id:ID!):A @stitch(key: "id") }
       |
       bravo = %|
         type T { id:ID! b:String }
@@ -331,13 +332,16 @@ def test_to_definition_annotates_schema
       assert @schema_sdl.include?("directive @resolver")
       assert @schema_sdl.include?("directive @source")
       assert @schema_sdl.include?(squish_string(%|
-        type T @resolver(location: "alpha", key: "id", field: "a", arg: "id")
-               @resolver(location: "bravo", key: "id", field: "b", arg: "id") {
+        interface A @resolver(location: "alpha", key: "id", field: "a", arg: "id") {
+      |))
+      assert @schema_sdl.include?(squish_string(%|
+        type T implements A @resolver(location: "bravo", key: "id", field: "b", arg: "id")
+                            @resolver(typeName: "A", location: "alpha", key: "id", field: "a", arg: "id") {
       |))
       assert @schema_sdl.include?(%|id: ID! @source(location: "alpha") @source(location: "bravo")|)
       assert @schema_sdl.include?(%|a: String @source(location: "alpha")|)
       assert @schema_sdl.include?(%|b: String @source(location: "bravo")|)
-      assert @schema_sdl.include?(%|a(id: ID!): T @source(location: "alpha")|)
+      assert @schema_sdl.include?(%|a(id: ID!): A @source(location: "alpha")|)
       assert @schema_sdl.include?(%|b(id: ID!): T @source(location: "bravo")|)
     end