Support $project exclusion of nested fields.

[Gaff]

If I have a document like so:

{
  "foo":  { "bar" :1, "bas": 1}
}

and I do: $project("foo.bas":0)

I should get back:

{
   "foo": {"bar":1}
}

This isn't working because Projection.projectDoucment() in the if(onlyExclusions(...)){...} clause takes a simplistic view on how to remove fields.

There's plenty of code in the same class for handling nested fields - maybe it can be changed to work with exclusions as well as inclusions?

[bwaldvogel]

I’ve reworked the $project staging handling to support exclusion/inclusion of nested fields.
Could you give 209a4b1 a try?

[bwaldvogel]

The change is part of v1.26.0.

[Gaff]

HI thanks - finally got back on this. I see it works for aggregations, but not for a vanilla project. I'll raise a separate ticket.

(Also since I'm here, is it worth testing this on arrays:

{
  "foo": [{"a":1}, {"b:1}]
}

and I do: $project("foo.b":0)

I should get back:

{
   "foo": [{"a":1}]
}

)