fix: fixes for embedded resources within unions (#2676)

Author: jsw800

lib/ash/actions/read/read.ex

@@ -1357,9 +1357,23 @@ defmodule Ash.Actions.Read do
         end)
       end)
 
+    # Ensure loadable attributes are included in load_through for cleanup,
+    # even if they weren't explicitly in the query's load_through.
+    # This matches what load_through_attributes does dynamically.
+    attribute_load_through =
+      resource
+      |> Ash.Resource.Info.attributes()
+      |> Enum.filter(fn %{name: name, type: type, constraints: constraints} ->
+        Ash.Type.can_load?(type, constraints) && (is_nil(query.select) || name in query.select)
+      end)
+      |> Enum.map(& &1.name)
+      |> Enum.reduce(query.load_through[:attribute] || %{}, fn name, acc ->
+        Map.put_new(acc, name, [])
+      end)
+
     records =
       Enum.reduce(
-        query.load_through[:attribute] || %{},
+        attribute_load_through,
         records,
         fn {attr_name, further_load}, records ->
           attribute = Ash.Resource.Info.attribute(resource, attr_name)

lib/ash/type/union.ex

@@ -464,11 +464,10 @@ defmodule Ash.Type.Union do
     end
   end
 
-  @impl true
-  def load(unions, [], _, _), do: {:ok, unions}
-
   @impl true
   def load(unions, load, constraints, context) do
+    load = load || []
+
     if Enum.any?(constraints[:types], fn {_name, config} ->
          Ash.Type.can_load?(config[:type], config[:constraints])
        end) do
@@ -1317,6 +1316,8 @@ defmodule Ash.Type.Union do
          {:ok, type_config} <- Keyword.fetch(type_configs, type_name),
          {:ok, type} <- Keyword.fetch(type_config, :type),
          type_constraints <- Keyword.get(type_config, :constraints, []),
+         type_constraints <-
+           Keyword.put(type_constraints, :__union_tag__, type_config[:tag]),
          type <- Ash.Type.get_type(type),
          {:ok, value} <- Ash.Type.prepare_change(type, old_value, new_value, type_constraints) do
       {:ok, %Ash.Union{type: type_name, value: value}}
@@ -1332,6 +1333,8 @@ defmodule Ash.Type.Union do
          {:ok, type_config} <- Keyword.fetch(type_configs, type_name),
          {:ok, type} <- Keyword.fetch(type_config, :type),
          type_constraints <- Keyword.get(type_config, :constraints, []),
+         type_constraints <-
+           Keyword.put(type_constraints, :__union_tag__, type_config[:tag]),
          type <- Ash.Type.get_type(type),
          {:ok, value} <- Ash.Type.prepare_change(type, nil, new_value, type_constraints) do
       {:ok, %Ash.Union{type: type_name, value: value}}