fix: map JSONSchema spec naming convention to snake_case when names f…

…rom schema_extra are not found

litestar/_openapi/schema_generation/schema.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import re
 from collections import deque
 from copy import copy
 from datetime import date, datetime, time, timedelta
@@ -139,6 +140,11 @@
 }
 
 
+def _jsonschema_to_propname(s: str) -> str:
+    """Given a string that matches the mixedCase convention used by the JSONSchema spec, convert to snake case as used here"""
+    return re.sub(r"([a-z])([A-Z])", lambda match: f"{match[1]}_{match[2].lower()}", s)
+
+
 def _types_in_list(lst: list[Any]) -> list[OpenAPIType] | OpenAPIType:
     """Extract unique OpenAPITypes present in the values of a list.
 
@@ -593,9 +599,12 @@ def process_schema_result(self, field: FieldDefinition, schema: Schema) -> Schem
             if isinstance(field.kwarg_definition, KwargDefinition) and (extra := field.kwarg_definition.schema_extra):
                 for schema_key, value in extra.items():
                     if not hasattr(schema, schema_key):
-                        raise ValueError(
-                            f"`schema_extra` declares key `{schema_key}` which does not exist in `Schema` object"
-                        )
+                        if hasattr(schema, (amended_key := _jsonschema_to_propname(schema_key))):
+                            schema_key = amended_key
+                        else:
+                            raise ValueError(
+                                f"`schema_extra` declares key `{schema_key}` which does not exist in `Schema` object"
+                            )
                     setattr(schema, schema_key, value)
 
         if schema.default is None and field.default is not Empty: