Instead of relying on the cpp_class workaround to simulate a server parameter of type IDL enum with this syntax:

planRankerMode:
description: "Control ranking method of query plans."
set_at: [ startup, runtime ]
cpp_class:
name: QueryPlanRankerMode
data: synchronized_value<QueryPlanRankerModeEnum>
default:
expr: QueryPlanRankerModeEnum::kMultiPlanning
redact: false

You can now use this syntax instead (without adding a separate class and append/setFromString method definitions).

planRankerMode:
description: "Control ranking method of query plans."
set_at: [ startup, runtime ]
cpp_varname: planRankerMode
cpp_vartype: synchronized_value<QueryPlanRankerModeEnum>

default:
expr: QueryPlanRankerModeEnum::kMultiPlanning
redact: false
 
Need to delete the now unnecessary code added for the workaround from before. This includes deleting plan_ranker_mode.cpp and replacing a line in query_knob_configuration.cpp with _planRankerMode = *planRankerMode;