Improved Elixir Atom Generation (#20229)

* Update ElixirClientCodegen.java

* Refine the regular expression for atoms

The original regex incorrectly matched `@atom` (unquoted atoms
cannot begin with @). However, through testing with `iex`, it also turns out that the atom
`:@` is legal.

The following atoms will now be quoted that would have been
incorrectly not quoted:

- `:@type`

* Add model to petstore client to test new atom creation regex pattern

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ElixirClientCodegen.java

@@ -48,7 +48,7 @@ import static org.openapitools.codegen.utils.StringUtils.underscore;
 public class ElixirClientCodegen extends DefaultCodegen {
     private final Logger LOGGER = LoggerFactory.getLogger(ElixirClientCodegen.class);
 
-    private final Pattern simpleAtomPattern = Pattern.compile("\\A(?:(?:[_@\\p{Alpha}][_@\\p{Alnum}]*[?!]?)|-)\\z");
+    private final Pattern simpleAtomPattern = Pattern.compile("\\A(?:(?:[_\\p{Alpha}][_@\\p{Alnum}]*[?!]?)|-|@)\\z");
 
     @Setter protected String packageVersion = "1.0.0";
     @Setter protected String moduleName;

samples/client/petstore/elixir/.openapi-generator/FILES

@@ -17,6 +17,7 @@ lib/openapi_petstore/model/_special_model_name_.ex
 lib/openapi_petstore/model/additional_properties_class.ex
 lib/openapi_petstore/model/all_of_with_single_ref.ex
 lib/openapi_petstore/model/animal.ex
+lib/openapi_petstore/model/any.ex
 lib/openapi_petstore/model/api_response.ex
 lib/openapi_petstore/model/array_of_array_of_number_only.ex
 lib/openapi_petstore/model/array_of_number_only.ex

samples/client/petstore/elixir/lib/openapi_petstore/model/any.ex

@@ -0,0 +1,22 @@
+# NOTE: This file is auto generated by OpenAPI Generator 7.11.0-SNAPSHOT (https://openapi-generator.tech).
+# Do not edit this file manually.
+
+defmodule OpenapiPetstore.Model.Any do
+  @moduledoc """
+  
+  """
+
+  @derive Jason.Encoder
+  defstruct [
+    :"@type"
+  ]
+
+  @type t :: %__MODULE__{
+    :"@type" => String.t | nil
+  }
+
+  def decode(value) do
+    value
+  end
+end
+

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

@@ -0,0 +1,14 @@
+defmodule AnyTest do
+  use ExUnit.Case, async: true
+  alias OpenapiPetstore.Model.Any, as: Model
+
+  test "decode all properties (not nil)" do
+    assert %Model{
+             "@type": "3fa85f64-5717-4562-b3fc-2c963f66afa6"
+           }
+           |> Model.decode() ==
+             %Model{
+               "@type": "3fa85f64-5717-4562-b3fc-2c963f66afa6"
+             }
+  end
+end