fix: correctly carry over first primary key attribute type and constr…

…aints (#36)

The main problem in 7e825a1 was using the `attributes` variable to detect the PK (which only contains attrs from `attributes_as_attributes`).

This commit also fixes an issue on the generated `:has_many` relationsip when the resource is using a PK other than `:id`.

lib/resource/transformers/create_version_resource.ex

@@ -46,18 +46,10 @@ defmodule AshPaperTrail.Resource.Transformers.CreateVersionResource do
 
     mixin = AshPaperTrail.Resource.Info.mixin(dsl_state) || AshPaperTrail.EmptyUse
 
-    first_pkey_attr = Enum.find(attributes, & &1.primary_key?)
-
-    first_pkey_attr_type =
-      first_pkey_attr && first_pkey_attr.type
-
-    first_pkey_attr_constraints =
-      first_pkey_attr && first_pkey_attr.constraints
-
     destination_attribute =
       case Ash.Resource.Info.primary_key(dsl_state) do
         [key] ->
-          key
+          Ash.Resource.Info.attribute(dsl_state, key)
 
         keys ->
           raise Spark.Error.DslError,
@@ -171,11 +163,9 @@ defmodule AshPaperTrail.Resource.Transformers.CreateVersionResource do
             end
           end
 
-          unless unquote(is_nil(first_pkey_attr)) do
-            attribute :version_source_id, unquote(Macro.escape(first_pkey_attr_type)) do
-              constraints unquote(Macro.escape(first_pkey_attr_constraints))
-              allow_nil? false
-            end
+          attribute :version_source_id, unquote(Macro.escape(destination_attribute.type)) do
+            constraints unquote(Macro.escape(destination_attribute.constraints))
+            allow_nil? false
           end
 
           attribute :changes, :map do
@@ -192,7 +182,7 @@ defmodule AshPaperTrail.Resource.Transformers.CreateVersionResource do
 
         relationships do
           belongs_to :version_source, unquote(module) do
-            destination_attribute(unquote(destination_attribute))
+            destination_attribute(unquote(destination_attribute.name))
             allow_nil?(false)
             attribute_writable?(true)
             source_attribute(:version_source_id)

lib/resource/transformers/relate_version_resource.ex

@@ -5,11 +5,13 @@ defmodule AshPaperTrail.Resource.Transformers.RelateVersionResource do
 
   # sobelow_skip ["DOS.StringToAtom"]
   def transform(dsl_state) do
-    with {:ok, relationship} <-
+    with {:ok, source_attribute} <- validate_source_attribute(dsl_state),
+         {:ok, relationship} <-
            Transformer.build_entity(Ash.Resource.Dsl, [:relationships], :has_many,
              name: :paper_trail_versions,
              destination: AshPaperTrail.Resource.Info.version_resource(dsl_state),
-             destination_attribute: :version_source_id
+             destination_attribute: :version_source_id,
+             source_attribute: source_attribute
            ) do
       {:ok,
        Transformer.add_entity(dsl_state, [:relationships], %{
@@ -23,4 +25,15 @@ defmodule AshPaperTrail.Resource.Transformers.RelateVersionResource do
   def before?(_), do: false
 
   def after?(_), do: true
+
+  defp validate_source_attribute(dsl_state) do
+    case Ash.Resource.Info.primary_key(dsl_state) do
+      [key] ->
+        {:ok, key}
+
+      keys ->
+        {:error,
+         "Only resources with a single primary key are currently supported. Got keys #{inspect(keys)}"}
+    end
+  end
 end

test/ash_paper_trail/resource/transformers/create_version_resource_test.exs

@@ -0,0 +1,46 @@
+defmodule AshPaperTrail.Resource.Transformers.CreateVersionResourceTest do
+  use ExUnit.Case
+
+  defmodule Tag do
+    use Ash.Resource,
+      data_layer: Ash.DataLayer.Ets,
+      extensions: [AshPaperTrail.Resource],
+      validate_api_inclusion?: false
+
+    ets do
+      private? true
+    end
+
+    attributes do
+      attribute :name, :string do
+        allow_nil? false
+        primary_key? true
+        constraints max_length: 20
+      end
+    end
+  end
+
+  defmodule Api do
+    use Ash.Api, extensions: [AshPaperTrail.Api], validate_config_inclusion?: false
+
+    resources do
+      resource Tag
+      resource Tag.Version
+    end
+  end
+
+  describe "attribute :version_source_id" do
+    setup do
+      version_source_id = Ash.Resource.Info.attribute(Tag.Version, :version_source_id)
+      [version_source_id: version_source_id]
+    end
+
+    test "uses resource primary key type", %{version_source_id: version_source_id} do
+      assert version_source_id.type == Ash.Type.String
+    end
+
+    test "uses resource primary key constraints", %{version_source_id: version_source_id} do
+      assert version_source_id.constraints == [allow_empty?: false, trim?: true, max_length: 20]
+    end
+  end
+end