- 
    Type:
Bug
 - 
    Resolution: Fixed
 - 
    Priority:
Major - P3
 - 
    Affects Version/s: 4.2.0-rc2
 - 
    Component/s: Aggregation Framework
 
- 
        Fully Compatible
 - 
        ALL
 - 
        Query 2019-07-15, Query 2019-07-29
 - 
        None
 
- 
        None
 - 
        None
 - 
        None
 - 
        None
 - 
        None
 - 
        None
 
db.example.update({_id:1}, [     {$set:{ } } ])
WriteResult({ ...
   "writeError" : {
	"code" : 40177,
	"errmsg" : "Invalid $addFields :: caused by :: specification must have at least one field"
	}
})
Typing $set and getting an error for $addFields can be confusing. Would be cleaner to use the same stage name as user provided (especially when it's a one-to-one alias).