Fix casting non-objects against discriminator #551

lib/open_api_spex/cast/discriminator.ex

@@ -37,7 +37,7 @@ defmodule OpenApiSpex.Cast.Discriminator do
     end
   end
 
-  defp cast_discriminator(%_{value: value, schema: schema} = ctx) do
+  defp cast_discriminator(%_{value: %{} = value, schema: schema} = ctx) do
     {discriminator_property, mappings} = discriminator_details(schema)
 
     case value["#{discriminator_property}"] || value[discriminator_property] do
@@ -53,6 +53,10 @@ defmodule OpenApiSpex.Cast.Discriminator do
     end
   end
 
+  defp cast_discriminator(ctx) do
+    Cast.error(ctx, {:invalid_type, :object})
+  end
+
   # When the composite key `allOf` is set we have to cast all the schemas even when the discriminator is set
   defp cast_composition(
          %_{schema: %{allOf: [_ | _]}} = composite_ctx,

test/cast/discriminator_test.exs

@@ -168,6 +168,18 @@ defmodule OpenApiSpex.CastDiscriminatorTest do
               ]} = cast(value: input_value, schema: discriminator_schema)
     end
 
+    test "value is not an object", %{schemas: %{dog: dog, wolf: wolf, cat: cat}} do
+      input_value = "this is a string but discriminator only works on objects"
+
+      discriminator_schema =
+        build_discriminator_schema([dog, wolf, cat], :anyOf, String.to_atom(@discriminator), nil)
+
+      assert {:error, [error]} = cast(value: input_value, schema: discriminator_schema)
+      assert error.reason == :invalid_type
+      assert error.type == :object
+      assert error.value == input_value
+    end
+
     test "invalid property on discriminator schema", %{
       schemas: %{dog: dog, wolf: wolf}
     } do