fix: Make sure request bodies without explicit names are named 'body'

The `Parameter` class now provides default Python names based on the parameter location when the original name is empty. This prevents parameters from having an empty string as their Python name, especially for request bodies defined without a top-level name.

Close #2213

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 834850255

tests/unittests/tools/openapi_tool/openapi_spec_parser/test_operation_parser.py

@@ -164,6 +164,40 @@ def test_process_request_body_no_name():
   assert parser._params[0].param_location == 'body'
 
 
+def test_process_request_body_one_of_schema_assigns_name():
+  """Ensures oneOf bodies result in a named parameter."""
+  operation = Operation(
+      operationId='one_of_request',
+      requestBody=RequestBody(
+          content={
+              'application/json': MediaType(
+                  schema=Schema(
+                      oneOf=[
+                          Schema(
+                              type='object',
+                              properties={
+                                  'type': Schema(type='string'),
+                                  'stage': Schema(type='string'),
+                              },
+                          )
+                      ],
+                      discriminator={'propertyName': 'type'},
+                  )
+              )
+          }
+      ),
+      responses={'200': Response(description='ok')},
+  )
+  parser = OperationParser(operation)
+  params = parser.get_parameters()
+  assert len(params) == 1
+  assert params[0].original_name == 'body'
+  assert params[0].py_name == 'body'
+  schema = parser.get_json_schema()
+  assert 'body' in schema['properties']
+  assert '' not in schema['properties']
+
+
 def test_process_request_body_empty_object():
   """Test _process_request_body with a schema that is of type object but with no properties."""
   operation = Operation(