[elixir] fixes outer enum bug #16412 (#20587)

modules/openapi-generator/src/main/resources/elixir/deserializer.ex.mustache

@@ -91,8 +91,12 @@ defmodule {{moduleName}}.Deserializer do
     end
   end
 
-  defp to_struct(map_or_list, module)
+  defp to_struct(value, module)
   defp to_struct(nil, _), do: nil
+  
+  defp to_struct(binary, module) when is_binary(binary) and is_atom(module) do
+    module.decode(binary)
+  end
 
   defp to_struct(list, module) when is_list(list) and is_atom(module) do
     Enum.map(list, &to_struct(&1, module))

samples/client/petstore/elixir/lib/openapi_petstore/deserializer.ex

@@ -93,8 +93,12 @@ defmodule OpenapiPetstore.Deserializer do
     end
   end
 
-  defp to_struct(map_or_list, module)
+  defp to_struct(value, module)
   defp to_struct(nil, _), do: nil
+  
+  defp to_struct(binary, module) when is_binary(binary) and is_atom(module) do
+    module.decode(binary)
+  end
 
   defp to_struct(list, module) when is_list(list) and is_atom(module) do
     Enum.map(list, &to_struct(&1, module))

samples/client/petstore/elixir/test/outer_enum_test.exs

@@ -0,0 +1,23 @@
+defmodule OuterEnumTest do
+  use ExUnit.Case, async: true
+
+  alias OpenapiPetstore.Deserializer
+  alias OpenapiPetstore.Model.EnumTest
+
+  @valid_json """
+  {
+    "enum_string": "UPPER",
+    "outerEnum": "placed"
+  }
+  """
+
+  @tag timeout: :infinity
+  test "jason_decode/2 with valid JSON" do
+    assert Deserializer.jason_decode(@valid_json, EnumTest) ==
+             {:ok,
+              %EnumTest{
+                enum_string: "UPPER",
+                outerEnum: "placed"
+              }}
+  end
+end