Problem Statement/Rationale

The translation of an aggregation using the mongo shell appears incorrect. It provides the following example syntax for an aggregation:

mongo 'mongodb://localhost:27017' --eval "db = db.getSiblingDB('db');
db.collection.aggregate({                                            
  'x': new NumberLong(0),                                            
  'y': new ObjectId()                                                
});"                                                                 

Aggregation should be using a pipeline represented as an array though. Also, this needs the $match stage (assuming this is meant to be a filter).

Actually executing this yields the following error:

uncaught exception: Error: command failed: {
	"ok" : 0,
	"errmsg" : "A pipeline stage specification object must contain exactly one field.",
	"code" : 40323,
	"codeName" : "Location40323"
} : aggregate failed :

Additional Notes

While this ticket only covers the shell, the other examples look like they might have the same issue, since none of them specify $match or use arrays for the pipeline. I haven't personally tested them yet though.

More broadly speaking, it seems like we might want to consider running integration tests using the generated output to ensure they're correct.