Error when using a NegatedPropertySet with reverse paths in SPARQL

[william-vw]

When running the following using rdflib v.7.1.4:

import rdflib
g = rdflib.Graph()
g.parse(data="""
<http://example.org/gmark/C> <http://example.org/gmark/p2> <http://example.org/gmark/D> .
<http://example.org/gmark/B> <http://example.org/gmark/p1> <http://example.org/gmark/C> .
<http://example.org/gmark/A> <http://example.org/gmark/p0> <http://example.org/gmark/B> .        
""")

query = """
PREFIX : <http://example.org/gmark/> 
SELECT *
WHERE {
    ?x1 !(:p1|^:p2) ?x2
}"""

qres = g.query(query)
for row in qres:
    print(row)

Note the ^ in the NegatedPropertySet; when dropping this the code works. AFAIK it is proper syntax. I also believe it does not raise an error during parsing but rather during execution.

This code gives the following error:

---------------------------------------------------------------------------
Exception                                 Traceback (most recent call last)
Cell In[3], [line 17](vscode-notebook-cell:?execution_count=3&line=17)
      [9](vscode-notebook-cell:?execution_count=3&line=9) query = """
     [10](vscode-notebook-cell:?execution_count=3&line=10) PREFIX : <[http://example.org/gmark/>](http://example.org/gmark/%3E) 
     [11](vscode-notebook-cell:?execution_count=3&line=11) SELECT *
     [12](vscode-notebook-cell:?execution_count=3&line=12) WHERE {
     [13](vscode-notebook-cell:?execution_count=3&line=13)     ?x1 !(:p1|^:p2) ?x2
     [14](vscode-notebook-cell:?execution_count=3&line=14) }"""
     [16](vscode-notebook-cell:?execution_count=3&line=16) qres = g.query(query)
---> [17](vscode-notebook-cell:?execution_count=3&line=17) for row in qres:
     [18](vscode-notebook-cell:?execution_count=3&line=18)     print(row)

File /opt/anaconda3/lib/python3.12/site-packages/rdflib/query.py:372, in Result.__iter__(self)
    [368](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/query.py:368) elif self.type == "SELECT":
    [369](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/query.py:369)     # this iterates over ResultRows of variable bindings
    [371](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/query.py:371)     if self._genbindings:
--> [372](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/query.py:372)         for b in self._genbindings:
    [373](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/query.py:373)             if b:  # don't add a result row in case of empty binding {}
    [374](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/query.py:374)                 self._bindings.append(b)

File /opt/anaconda3/lib/python3.12/site-packages/rdflib/plugins/sparql/evaluate.py:574, in <genexpr>(.0)
    [572](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/plugins/sparql/evaluate.py:572) def evalProject(ctx: QueryContext, project: CompValue):
    [573](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/plugins/sparql/evaluate.py:573)     res = evalPart(ctx, project.p)
--> [574](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/plugins/sparql/evaluate.py:574)     return (row.project(project.PV) for row in res)

File /opt/anaconda3/lib/python3.12/site-packages/rdflib/plugins/sparql/evaluate.py:97, in evalBGP(ctx, bgp)
     [93](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/plugins/sparql/evaluate.py:93) _o = ctx[o]
     [95](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/plugins/sparql/evaluate.py:95) # type error: Item "None" of "Optional[Graph]" has no attribute "triples"
     [96](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/plugins/sparql/evaluate.py:96) # type Argument 1 to "triples" of "Graph" has incompatible type "Tuple[Union[str, Path, None], Union[str, Path, None], Union[str, Path, None]]"; expected "Tuple[Optional[Node], Optional[Node], Optional[Node]]"
---> [97](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/plugins/sparql/evaluate.py:97) for ss, sp, so in ctx.graph.triples((_s, _p, _o)):  # type: ignore[union-attr, arg-type]
     [98](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/plugins/sparql/evaluate.py:98)     if None in (_s, _p, _o):
     [99](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/plugins/sparql/evaluate.py:99)         c = ctx.push()

File /opt/anaconda3/lib/python3.12/site-packages/rdflib/graph.py:635, in Graph.triples(self, triple)
    [633](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/graph.py:633) s, p, o = triple
    [634](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/graph.py:634) if isinstance(p, Path):
--> [635](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/graph.py:635)     for _s, _o in p.eval(self, s, o):
    [636](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/graph.py:636)         yield _s, p, _o
    [637](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/graph.py:637) else:

File /opt/anaconda3/lib/python3.12/site-packages/rdflib/paths.py:507, in NegatedPath.eval(self, graph, subj, obj)
    [505](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/paths.py:505)             break
    [506](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/paths.py:506)     else:
--> [507](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/paths.py:507)         raise Exception("Invalid path in NegatedPath: %s" % a)
    [508](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/paths.py:508) else:
    [509](https://file+.vscode-resource.vscode-cdn.net/opt/anaconda3/lib/python3.12/site-packages/rdflib/paths.py:509)     yield s, o

Exception: Invalid path in NegatedPath: InversePath_InversePath_{}

Any help would be appreciated!