From f03b6a4370d741b23cdd1b7432cb1fdc6f10eaa5 Mon Sep 17 00:00:00 2001
From: Robert Graff <robert@workingdemo.com>
Date: Wed, 25 Oct 2023 05:31:25 -0700
Subject: [PATCH] fix: handle builtin types in unions (#752)

---
 .gitpod.yml              |  5 ++++
 lib/ash/type/union.ex    |  2 ++
 test/type/union_test.exs | 56 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+)
 create mode 100644 .gitpod.yml

diff --git a/.gitpod.yml b/.gitpod.yml
new file mode 100644
index 00000000..326062b1
--- /dev/null
+++ b/.gitpod.yml
@@ -0,0 +1,5 @@
+image: elixir:latest
+  
+tasks:
+  - init: mix deps.get && mix compile
+    command: iex -S mix
\ No newline at end of file
diff --git a/lib/ash/type/union.ex b/lib/ash/type/union.ex
index 31ffa4b6..9addfc3a 100644
--- a/lib/ash/type/union.ex
+++ b/lib/ash/type/union.ex
@@ -521,6 +521,7 @@ 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 <- Ash.Type.get_type(type),
          {:ok, new_value} <- type.handle_change(nil, new_value, type_constraints) do
       {:ok, %Ash.Union{type: type_name, value: new_value}}
     end
@@ -574,6 +575,7 @@ 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 <- Ash.Type.get_type(type),
          {:ok, value} <- type.prepare_change(old_value, new_value, type_constraints) do
       {:ok, %Ash.Union{type: type_name, value: value}}
     end
diff --git a/test/type/union_test.exs b/test/type/union_test.exs
index 78d010aa..d5a2c4f1 100644
--- a/test/type/union_test.exs
+++ b/test/type/union_test.exs
@@ -84,6 +84,62 @@ defmodule Ash.Test.Type.UnionTest do
     assert {:error, _} = Ash.Type.cast_input(:union, 11, constraints)
   end
 
+  test "it handles changes between native types" do
+    constraints = [
+      types: [
+        foo: [
+          type: :integer
+        ],
+        bar: [
+          type: :string
+        ]
+      ]
+    ]
+
+    assert {:ok, %Ash.Union{type: :bar, value: "bar"}} =
+             Ash.Type.Union.prepare_change(
+               %Ash.Union{type: :foo, value: 1},
+               "bar",
+               constraints
+             )
+
+    assert {:ok, %Ash.Union{type: :bar, value: "bar"}} =
+             Ash.Type.Union.handle_change(
+               %Ash.Union{type: :foo, value: 1},
+               %Ash.Union{type: :bar, value: "bar"},
+               constraints
+             )
+  end
+
+  test "it handles changes between native and tagged types" do
+    constraints = [
+      types: [
+        foo: [
+          type: Foo,
+          tag: :type,
+          tag_value: :foo
+        ],
+        bar: [
+          type: :string
+        ]
+      ]
+    ]
+
+    assert {:ok, %Ash.Union{type: :bar, value: "bar"}} =
+             Ash.Type.Union.prepare_change(
+               %Ash.Union{type: :foo, value: %Foo{}},
+               "bar",
+               constraints
+             )
+
+    assert {:ok, %Ash.Union{type: :bar, value: "bar"}} =
+             Ash.Type.Union.handle_change(
+               %Ash.Union{type: :foo, value: %{}},
+               %Ash.Union{type: :bar, value: "bar"},
+               constraints
+             )
+  end
+
   test "it handles tagged types" do
     constraints = [
       types: [