From 892b3adad8caf14d286f9a20579b5391e0b832af Mon Sep 17 00:00:00 2001
From: Skander Mzali <skanderm@gmail.com>
Date: Thu, 31 Jul 2025 17:10:49 -0700
Subject: [PATCH 1/2] Add failing test for a calculation with a :struct return
 type

---
 test/read_test.exs                      | 30 +++++++++++++++++++++++++
 test/support/resources/post.ex          | 10 +++++++++
 test/support/types/unreferenced_type.ex | 13 +++++++++++
 3 files changed, 53 insertions(+)
 create mode 100644 test/support/types/unreferenced_type.ex

diff --git a/test/read_test.exs b/test/read_test.exs
index e0ad5c1e..150395e9 100644
--- a/test/read_test.exs
+++ b/test/read_test.exs
@@ -1625,4 +1625,34 @@ defmodule AshGraphql.ReadTest do
              } = result
     end
   end
+
+  describe "calculations" do
+    test "loads calculated struct type that uses constraint" do
+      post =
+        AshGraphql.Test.Post
+        |> Ash.Changeset.for_create(:create,
+          text: "a",
+          published: true
+        )
+        |> Ash.create!()
+
+      resp =
+        """
+        query postLibrary {
+          postLibrary(sort: {field: TEXT}) {
+            structCalc {
+              some
+            }
+          }
+        }
+        """
+        |> Absinthe.run(AshGraphql.Test.Schema)
+
+      assert {:ok, result} = resp
+
+      refute Map.has_key?(result, :errors)
+
+      assert %{data: %{"postLibrary" => [%{"structCalc" => %{"some" => "string"}}]}} = result
+    end
+  end
 end
diff --git a/test/support/resources/post.ex b/test/support/resources/post.ex
index 3179ee91..095e4a70 100644
--- a/test/support/resources/post.ex
+++ b/test/support/resources/post.ex
@@ -625,6 +625,16 @@ defmodule AshGraphql.Test.Post do
       end,
       public?: true
     )
+
+    calculate(
+      :struct_calc,
+      :struct,
+      fn records, _ ->
+        Enum.map(records, fn _ -> %{some: "string"} end)
+      end,
+      public?: true,
+      constraints: [instance_of: AshGraphql.Test.UnreferencedType]
+    )
   end
 
   aggregates do
diff --git a/test/support/types/unreferenced_type.ex b/test/support/types/unreferenced_type.ex
new file mode 100644
index 00000000..1232001f
--- /dev/null
+++ b/test/support/types/unreferenced_type.ex
@@ -0,0 +1,13 @@
+defmodule AshGraphql.Test.UnreferencedType do
+  @moduledoc false
+  use Ash.Type.NewType,
+    subtype_of: :map,
+    constraints: [
+      fields: [
+        some: [
+          type: :string,
+          allow_nil?: false
+        ]
+      ]
+    ]
+end

From 8bb77dfebba945fa6d7cc81bf4a2ffe1d40844e0 Mon Sep 17 00:00:00 2001
From: Skander Mzali <skanderm@gmail.com>
Date: Thu, 31 Jul 2025 17:58:47 -0700
Subject: [PATCH 2/2] chore: traverse instance_of in constraints when present
 (not working yet)

---
 lib/ash_graphql.ex | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/lib/ash_graphql.ex b/lib/ash_graphql.ex
index a64c8039..84f18e13 100644
--- a/lib/ash_graphql.ex
+++ b/lib/ash_graphql.ex
@@ -748,6 +748,16 @@ defmodule AshGraphql do
         type = Ash.Type.NewType.subtype_of(type)
         nested_attrs(type, all_domains, constraints, already_checked)
 
+      type == Ash.Type.Struct && Keyword.has_key?(constraints, :instance_of) ->
+        type = Keyword.get(constraints, :instance_of)
+
+        if function_exported?(type, :subtype_constraints, 0) do
+          constraints = apply(type, :subtype_constraints, [])
+          nested_attrs(type, all_domains, constraints, already_checked)
+        else
+          {[], already_checked}
+        end
+
       true ->
         {[], already_checked}
     end