Issue 738: support empty publicID

[AnjoMan]

This adds support for specifying a publicID as '';
instead of evaluating the falsy-ness of the input,
we want to use the provided string, even if it is
''.

Fixes #738

Proposed Changes

• when the user specifies publicID as '', we should not trigger the None default behaviour

[coveralls]

Coverage increased (+0.01%) to 75.68% when pulling 7785f46 on AnjoMan:738-rdflib-ignores-empty-publicID into 56dc420 on RDFLib:master.

[coveralls]

Coverage increased (+0.01%) to 75.68% when pulling 7785f46 on AnjoMan:738-rdflib-ignores-empty-publicID into 56dc420 on RDFLib:master.

[coveralls]

Coverage decreased (-0.008%) to 75.659% when pulling 7785f46 on AnjoMan:738-rdflib-ignores-empty-publicID into 56dc420 on RDFLib:master.

[AnjoMan]

If you like this contribution, please add the #hacktoberfest-accepted label

[ashleysommer]

Hi @AnjoMan
This looks like a good change, we will discuss this more formally tomorrow at our RDFLib maintainers meeting. We will have to run some more tests internally to ensure everything in the RDF/XML serializer operates correctly after this change.

I'm sorry, we are not participating in DigitalOcean's Hacktoberfest campaign.

[ashleysommer]

Hi @AnjoMan
After discussing this, we have decided we will need to test this solution further. You have implemented the change just for the RDF/XML parser, but we need to test what happens if you use publicID="" for other parsers, like TRIG, or N3, or JSON-LD. While your change does fix the problem you are seeing, it could also potentially introduce breakages in unexpected places, so we need to be cautious about how to proceed with this.

[white-gecko]

As can be seen for the turtle example, with your fix we would introduce some inconsistency across the serializers. The fix does also not work in the same way for the current Turtle parser/notation3 parser as we call graph.absolutize() in this case.

What is the usecase for an emptyID?

In m eyes this relative URI thing without explicitly defining a base in the file is a tough problem.

[white-gecko]

This issue needs to be solved for all parsers at once.