[{"_id":ObjectId("5b7e0e259fceda195ba6d4ee"),"name1":"test","name2":"test","name3":"test","list":{"_id":"5b7dfee2130dd4ff45288875","name":"test1","name2":"test2","name3":"test3","name4":"test4"}}]

db.collection.aggregate([{$project:{"_id":0,"document":"$$CURRENT","list._id":"$$CURRENT.list._id","list.name":"$$CURRENT.list.name"}},{$project:{"document.list":0}},{$addFields:{"document.list._id":"$$CURRENT.list._id","document.list.name":"$$CURRENT.list.name",}},{$replaceRoot:{newRoot:"$document"}}])