ComparisonOperators should support isNull() [DATAMONGO-2619]

Daniel Theuke opened DATAMONGO-2619 and commented

Currently I have to this workaround:

when(ComparisonOperators.valueOf("$$child.v").equalTo(ctx -> null))
                            .then(new Document("type", "$$child.k"))
                            .otherwise(new Document()
                                    .append("type", "$$child.k")
                                    .append("version", "$$child.v")))

It would be nice if I could use something like this:

when(ComparisonOperators.valueOf("$$child.v").equalToValue(null))
                            .then(new Document("type", "$$child.k"))
                            .otherwise(new Document()
                                    .append("type", "$$child.k")
                                    .append("version", "$$child.v")))

or

when(ComparisonOperators.valueOf("$$child.v").isNull())
                            .then(new Document("type", "$$child.k"))
                            .otherwise(new Document()
                                    .append("type", "$$child.k")
                                    .append("version", "$$child.v")))

Expected ouput:

'if': {
	$eq: [
		'$$child.v',
		null
	]
},
then: {
	type: '$$child.k'
},
'else': {
	type: '$$child.k',
	version: '$$child.v'
}

Affects: 3.0.3 (Neumann SR3)