QueryBuilder: allow with_incoming/with_outgoing = None

[yakutovicha]

I propose to simplify the search for the nodes that don't have parents/children. This could be achieved by allowing with_incoming/with_outgoing parameters be set to None. Currently, this is not possible.

The way I currently search for StructureData that does not have parent nodes:

qbuild = QueryBuilder()

qbuild2 = QueryBuilder().append(StructureData, project=["id"], tag='structures')
qbuild2.append(Node, with_outgoing='structures')
processed_nodes = [n[0] for n in qbuild2.all()]
if processed_nodes:
    filters['id'] = {"!in": processed_nodes}
qbuild.append(self.what_query_for, filters=filters)

Would be cool to replace all of this by simply:

qbuild = QueryBuilder().append(StructureData, with_incoming=None)

[giovannipizzi]

It would be good to discuss how to extend the query builder also for similar but slightly similar queries.

E.g.: query for a node not have a given input link (e.g. not having a link with a given label, and/or type?)

[yakutovicha]

mentioning @lekah, @ramirezfranciscof in case you have ideas.

[lekah]

There was some code that was meant for these cases in the QB... It was removed in #3518 since it hadn't been updated after some ORM changes. If that code gets re-used, that needs to be fixed and it should be documented a bit more. But the code was solving that specific issue and could be reused to solve your problem. On the other hand, your code does work, so it's more of a convenience thing...

I would not use, however, your proposed solution of setting with_incoming to None, that is against the logic of the QB IMHO.