From a664778d8de3e7ed3175784963c91a98a42c824d Mon Sep 17 00:00:00 2001
From: Nick <nick.duitz@9elements.com>
Date: Wed, 10 Sep 2025 11:35:47 +0200
Subject: [PATCH] improve error for type mismatch

---
 lib/open_api_spex/cast/enum.ex  |  4 ++--
 lib/open_api_spex/cast/error.ex | 10 ++++++----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/lib/open_api_spex/cast/enum.ex b/lib/open_api_spex/cast/enum.ex
index b78c146c..f3a664ff 100644
--- a/lib/open_api_spex/cast/enum.ex
+++ b/lib/open_api_spex/cast/enum.ex
@@ -3,8 +3,8 @@ defmodule OpenApiSpex.Cast.Enum do
   alias OpenApiSpex.Cast
 
   def cast(ctx = %Cast{schema: %{enum: enum}, value: value}) do
-    case Enum.find(enum, {:error, :invalid_enum}, &equivalent?(&1, value)) do
-      {:error, :invalid_enum} -> Cast.error(ctx, {:invalid_enum})
+    case Enum.find(enum, {:error, :invalid_enum, enum, value}, &equivalent?(&1, value)) do
+      {:error, :invalid_enum, enum, value} -> Cast.error(ctx, {:invalid_enum, enum, value})
       found -> {:ok, found}
     end
   end
diff --git a/lib/open_api_spex/cast/error.ex b/lib/open_api_spex/cast/error.ex
index 49cefec0..e2501983 100644
--- a/lib/open_api_spex/cast/error.ex
+++ b/lib/open_api_spex/cast/error.ex
@@ -91,6 +91,7 @@ defmodule OpenApiSpex.Cast.Error do
   @type t :: %__MODULE__{
           reason: reason(),
           value: any(),
+          enum: any(),
           format: String.t(),
           name: String.t(),
           path: list(String.t()),
@@ -100,6 +101,7 @@ defmodule OpenApiSpex.Cast.Error do
 
   defstruct reason: nil,
             value: nil,
+            enum: [],
             format: nil,
             type: nil,
             name: nil,
@@ -196,8 +198,8 @@ defmodule OpenApiSpex.Cast.Error do
     |> add_context_fields(ctx)
   end
 
-  def new(ctx, {:invalid_enum}) do
-    %__MODULE__{reason: :invalid_enum}
+  def new(ctx, {:invalid_enum, enum, value}) do
+    %__MODULE__{reason: :invalid_enum, enum: enum, value: value}
     |> add_context_fields(ctx)
   end
 
@@ -329,8 +331,8 @@ defmodule OpenApiSpex.Cast.Error do
     "Invalid format. Expected #{inspect(format)}"
   end
 
-  def message(%{reason: :invalid_enum}) do
-    "Invalid value for enum"
+  def message(%{reason: :invalid_enum, enum: enum, value: value}) do
+    "Invalid value for enum, allowed_values: #{inspect(enum)}, got: #{inspect(value)}"
   end
 
   def message(%{reason: :polymorphic_failed, type: polymorphic_type}) do