From dbf871629588e89bc4ea45156aff016654a83359 Mon Sep 17 00:00:00 2001
From: Peter Shoukry <pshoukry@gmail.com>
Date: Sun, 21 Dec 2025 12:03:30 +0200
Subject: [PATCH] fix: add catch-all can?/3 clause for custom item actions

When using custom item_actions in an AshBackpex.LiveResource, the page
would crash with FunctionClauseError because the transformer only
generated can?/3 clauses for standard actions (:new, :index, :show,
:edit, :delete).

The fix adds a fallback can?/3 clause that:
- Returns true for actions that don't exist on the Ash resource
- Checks Ash authorization for actions that do exist on the resource

This mirrors the base Backpex.LiveResource behavior while integrating
with Ash's authorization system.
---
 .../transformers/generate_backpex.ex          | 19 ++++++++
 test/ash_backpex/authz_test.exs               | 14 ++++++
 test/support/test_live.ex                     | 43 +++++++++++++++++++
 3 files changed, 76 insertions(+)

diff --git a/lib/ash_backpex/live_resource/transformers/generate_backpex.ex b/lib/ash_backpex/live_resource/transformers/generate_backpex.ex
index 3cc6f82..60f9e3d 100644
--- a/lib/ash_backpex/live_resource/transformers/generate_backpex.ex
+++ b/lib/ash_backpex/live_resource/transformers/generate_backpex.ex
@@ -408,6 +408,25 @@ defmodule AshBackpex.LiveResource.Transformers.GenerateBackpex do
           def can?(_assigns, :delete, _item), do: false
         end
 
+        # Fallback for custom item actions and any other actions
+        # Checks Ash authorization if a matching action exists, otherwise allows by default
+        def can?(assigns, action, item) do
+          case Ash.Resource.Info.action(@resource, action) do
+            nil ->
+              true
+
+            ash_action ->
+              target =
+                if is_struct(item) and item.__struct__ == @resource do
+                  {item, ash_action.name}
+                else
+                  {@resource, ash_action.name}
+                end
+
+              Ash.can?(target, Map.get(assigns, :current_user))
+          end
+        end
+
         def maybe_default_options(assigns) do
           case assigns do
             %{field: {attribute_name, _field_cfg}} ->
diff --git a/test/ash_backpex/authz_test.exs b/test/ash_backpex/authz_test.exs
index 8ff3ae6..79c1d05 100644
--- a/test/ash_backpex/authz_test.exs
+++ b/test/ash_backpex/authz_test.exs
@@ -41,6 +41,20 @@ defmodule AshBackpex.AuthzTest do
     end
   end
 
+  describe "AshBackpex.LiveResource :: can? with custom item actions" do
+    test "returns true for unknown actions that don't exist on the resource" do
+      # :promote is not an Ash action on Item, so fallback returns true
+      assert TestCustomItemActionLive.can?(%{current_user: nil}, :promote, %{})
+      assert TestCustomItemActionLive.can?(%{current_user: nil}, :some_unknown_action, %{})
+    end
+
+    test "checks Ash authorization when action exists on resource" do
+      # :read exists on Item resource, so it checks Ash.can?
+      # Item has no policies, so it should return true
+      assert TestCustomItemActionLive.can?(%{current_user: nil}, :read, %{})
+    end
+  end
+
   describe "AshBackpex.Adapter :: it can" do
     test "list/3" do
       user = user()
diff --git a/test/support/test_live.ex b/test/support/test_live.ex
index f21b20a..fac88f1 100644
--- a/test/support/test_live.ex
+++ b/test/support/test_live.ex
@@ -113,3 +113,46 @@ defmodule TestLayout do
     """
   end
 end
+
+# Custom item action for testing can?/3 fallback
+defmodule TestPromoteItemAction do
+  @moduledoc false
+  use BackpexWeb, :item_action
+
+  @impl Backpex.ItemAction
+  def icon(assigns, _item) do
+    ~H"""
+    <Backpex.HTML.CoreComponents.icon
+      name="hero-arrow-up-circle"
+      class="h-5 w-5 cursor-pointer transition duration-75 hover:scale-110 hover:text-success"
+    />
+    """
+  end
+
+  @impl Backpex.ItemAction
+  def label(_assigns, _item), do: "Promote"
+
+  @impl Backpex.ItemAction
+  def handle(socket, _items, _data) do
+    {:ok, socket}
+  end
+end
+
+# LiveResource with custom item action for testing can?/3 fallback
+defmodule TestCustomItemActionLive do
+  @moduledoc false
+  use AshBackpex.LiveResource
+
+  backpex do
+    resource(AshBackpex.TestDomain.Item)
+    layout({TestLayout, :admin})
+
+    item_actions do
+      action :promote, TestPromoteItemAction
+    end
+
+    fields do
+      field(:name)
+    end
+  end
+end