$lookup() function throws an error when the property has a null value

[shrickus]

The incoming weather data object may contain some fields with null values -- like this:

{
  "temp": 22.7,
  "wind": 7,
  "gust": null,
  "timestamp": 1508971317377
}

I'm using the $lookup() function to find the "gust" value, with this expression:

{
	"x": $$.timestamp,
	"y": $lookup($$, "gust")
}

Instead of getting the property "y": null in the output object, this error is thrown instead:
Invalid operand to 'in': Object expected

Since I can use $$.gust to return the value null, this error is inconsistent and probably should be caught. I would prefer the null value to be returned, but it would also be acceptable to not create that field on the output object at all -- and would be consistent with the current behavior when trying to lookup a field that does not exist.

[andrew-coleman]

Thanks for raising this. Now fixed in v1.3.3