From 24cc008410e83dc4426f9c96cf5f38f81afed326 Mon Sep 17 00:00:00 2001
From: Zach Daniel <zach@zachdaniel.dev>
Date: Wed, 4 Sep 2024 20:51:54 -0400
Subject: [PATCH] improvement: ArgumentError for non-existent actions in
 `Ash.can?`

---
 lib/ash/can.ex | 32 +++++++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 7 deletions(-)

diff --git a/lib/ash/can.ex b/lib/ash/can.ex
index fac1c2ad..16c5d367 100644
--- a/lib/ash/can.ex
+++ b/lib/ash/can.ex
@@ -132,32 +132,50 @@ defmodule Ash.Can do
   defp resource_subject_input(action_or_query_or_changeset, domain, actor, opts) do
     case action_or_query_or_changeset do
       {resource, name} when is_atom(name) and is_atom(resource) ->
+        action =
+          Ash.Resource.Info.action(resource, name) ||
+            raise ArgumentError, "No such action #{name} on #{inspect(resource)}"
+
         resource_subject_input(
-          {resource, Ash.Resource.Info.action(resource, name), %{}},
+          {resource, action, %{}},
           domain,
           actor,
           opts
         )
 
-      {resource, name, input} when is_atom(name) and is_atom(resource) ->
+      {resource, name, input} when is_atom(name) and is_atom(resource) and not is_nil(name) ->
+        action =
+          Ash.Resource.Info.action(resource, name) ||
+            raise ArgumentError, "No such action #{name} on #{inspect(resource)}"
+
         resource_subject_input(
-          {resource, Ash.Resource.Info.action(resource, name), input},
+          {resource, action, input},
           domain,
           actor,
           opts
         )
 
-      {%resource{} = record, name} when is_atom(name) and is_atom(resource) ->
+      {%resource{} = record, name}
+      when is_atom(name) and is_atom(resource) and not is_nil(name) ->
+        action =
+          Ash.Resource.Info.action(resource, name) ||
+            raise ArgumentError, "No such action #{name} on #{inspect(resource)}"
+
         resource_subject_input(
-          {record, Ash.Resource.Info.action(resource, name), %{}},
+          {record, action, %{}},
           domain,
           actor,
           opts
         )
 
-      {%resource{} = record, name, input} when is_atom(name) and is_atom(resource) ->
+      {%resource{} = record, name, input}
+      when is_atom(name) and is_atom(resource) and not is_nil(name) ->
+        action =
+          Ash.Resource.Info.action(resource, name) ||
+            raise ArgumentError, "No such action #{name} on #{inspect(resource)}"
+
         resource_subject_input(
-          {record, Ash.Resource.Info.action(resource, name), input},
+          {record, action, input},
           domain,
           actor,
           opts