Fix title ignored when creating enums from merging allOf's or anyOf's objects (#2975)

* Fix x_enum_varnames ignored because class variable name was used insteaad of its alias

* Keep existing behavior when title isn't defined and the enum's type can be inferred and used as name

* Improve fix for unveiled incorrect behavior

---------

Co-authored-by: Antonio Spadaro <9268789+ilovelinux@users.noreply.github.com>

Author: ilovelinux

src/datamodel_code_generator/parser/jsonschema.py

@@ -854,8 +854,6 @@ def _extract_const_enum_from_combined(  # noqa: PLR0912
 
             if item.title:
                 varnames.append(item.title)
-            else:
-                varnames.append(str(const_value))
 
             if inferred_type is None and const_value is not None:
                 match const_value:
@@ -902,8 +900,7 @@ def _create_synthetic_enum_obj(
             enum=final_enum,
             title=original.title,
             description=original.description,
-            x_enum_varnames=final_varnames,
-            **({"default": original.default} if original.has_default else {}),
+            **({"x-enum-varnames": final_varnames} | ({"default": original.default} if original.has_default else {})),
         )
 
     def is_constraints_field(self, obj: JsonSchemaObject) -> bool:

tests/data/expected/main/jsonschema/oneof_const_enum_int.py

@@ -8,6 +8,6 @@
 
 
 class StatusCode(IntEnum):
-    integer_200 = 200
-    integer_404 = 404
-    integer_500 = 500
+    OK = 200
+    Not_Found = 404
+    Server_Error = 500