var x = db.runCommand({aggregate: "foo", pipeline: [
  {$project: {
//     doesn't work
//      date: {$isoDate: {year: 2012, month: 2, dayOfMonth: 4} } ,
/* // this worked - copy-pasted from testall.js
      testDate: {$isoDate:{
          year: "$year", month: "$month", dayOfMonth: "$dayOfMonth",
          hour: "$hour", minute: "$minutes", second: "$seconds"}}
*/
// this didn't
      testDate: {$isoDate:{
          year: 2012, month: "$month", dayOfMonth: "$dayOfMonth",
          hour: "$hour", minute: "$minutes", second: "$seconds"}}
  }}
]});

{
        "errmsg" : "exception: \"year\" numeric inclusion or exclusion must be 1
 or 0 (or boolean)",
        "code" : 15991,
        "ok" : 0
}