Memory store stores the resource object, not the semantic.

[ticapix]

Hello,

I'm not sure how to describe the issue, so here is a sample code

from rdflib import FOAF, Graph, Literal, URIRef


class MyId(URIRef): ...


g = Graph()

g.add((MyId("subject"), FOAF.name, Literal("bob")))

print(g.serialize())

assert (MyId("subject"), FOAF.name, Literal("bob")) in g  # ok
assert (URIRef("subject"), FOAF.name, Literal("bob")) in g  # fails

And the output

@prefix foaf: <http://xmlns.com/foaf/0.1/> .

<subject> foaf:name "bob" .

I was expecting the second assert to be True because in both case I'm looking for the subject <subject>.

PS: on the why I'm subclassing URIRef, it's to leverage static type checking with mypy when my functions are expecting ids that carry a special meaning.

Is it the expected behavior and should I take care of always passing URIRef object ?

This fix the issue but is a bit cumbersome.

g.add((URIRef(MyId("subject")), FOAF.name, Literal("bob")))

print(g.serialize())

assert (URIRef(MyId("subject")), FOAF.name, Literal("bob")) in g  # ok
assert (URIRef("subject"), FOAF.name, Literal("bob")) in g  # ok

[ticapix]

I think I found a way to make it work within a graph with this code

from typing import Any

from rdflib import FOAF, Graph, IdentifiedNode, Literal, URIRef


class MyId(URIRef):
    def __hash__(self) -> int:
        return super().__hash__()

    def __eq__(self, other: Any) -> bool:
        if isinstance(other, IdentifiedNode):
            return self.n3() == other.n3()
        return super().__eq__(other)


g = Graph()

g.add((MyId("subject"), FOAF.name, Literal("bob")))

print(g.serialize())

assert (MyId("subject"), FOAF.name, Literal("bob")) in g  # ok
assert (URIRef("subject"), FOAF.name, Literal("bob")) in g  # ok

Does it make sense to open a PR to add __eq__ (and __hash__) to IdentifiedNode class ?

[edmondchuc]

Could you please check if your solution works with SPARQL querying?

Related: #1332

[ticapix]

I think it does.

Without __eq__, it fails, with it, it runs.

from typing import Any

from rdflib import FOAF, Graph, IdentifiedNode, URIRef


class IRI(URIRef):
    """Internationalized Resource Identifier."""

    def __hash__(self) -> int:
        return super().__hash__()

    def __eq__(self, other: Any) -> bool:
        if isinstance(other, IdentifiedNode):
            return self.n3() == other.n3()
        return super().__eq__(other)

    def __repr__(self):
        """Format IRI."""
        return f"<{self.toPython()}>"


def test_uriref_subclass():
    graph = Graph()
    graph.add(
        (
            IRI("https://example.com/Alice"),
            IRI(FOAF.knows),
            IRI("https://example.com/Bob"),
        )
    )

    bindings = graph.query(
        "SELECT * WHERE { ?s <http://xmlns.com/foaf/0.1/knows> ?o . }",
    ).bindings

    # Here we see that bindings are empty: nothing was found.
    assert len(bindings) != 0

    for binding in bindings:
        print(binding)


test_uriref_subclass()

and output is

{rdflib.term.Variable('s'): <https://example.com/Alice>, rdflib.term.Variable('o'): <https://example.com/Bob>}

[ticapix]

Adding __eq__ also solve subclass of URIRef when used as graph.identifier in a dataset.

from rdflib import Dataset, URIRef


class MyId(URIRef):
    ...


ds = Dataset()
g1 = ds.graph(identifier=URIRef("mygraph"))
g2 = ds.graph(identifier=MyId("mygraph"))


assert len(list(ds.graphs())) == 2, ", ".join([repr(g.identifier) for g in ds.graphs()]) # fails with the message
# AssertionError: MyId('mygraph'), rdflib.term.URIRef('urn:x-rdflib:default'), rdflib.term.URIRef('mygraph')

from typing import Any

from rdflib import Dataset, IdentifiedNode, URIRef


class MyId(URIRef):
    def __hash__(self) -> int:
        return super().__hash__()

    def __eq__(self, other: Any) -> bool:
        if isinstance(other, IdentifiedNode):
            return self.n3() == other.n3()
        return super().__eq__(other)


ds = Dataset()
g1 = ds.graph(identifier=URIRef("mygraph"))
g2 = ds.graph(identifier=MyId("mygraph"))


assert len(list(ds.graphs())) == 2, ", ".join([repr(g.identifier) for g in ds.graphs()]) # ok