// projecting a non-existent subfield should work as it does in a query with projection
c = db.c;
c.drop();

c.save({a:[1]});
c.save({a:{c:1}});
c.save({a:[{c:1},{b:1,c:1},{c:1}]});
c.save({a:1});
c.save({b:1});

// assert the aggregation and the query produce the same thing
assert.eq(c.aggregate({$project:{'a.b':1}}).toArray(), c.find({}, {'a.b':1}).toArray());