N3 serializer "randomly" omits triple #1807
Description
There seems to be an issue with the notation3 serializer randomly omitting to serialize triples.
Given the following test created in test/test_n3_formula.py ...
import pytest
import rdflib
test_n3 = """@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix : <http://test/> .
{:a :b :c;a :foo} => {:a :d :c,?y} .
_:foo a rdfs:Class .
:a :d :c ."""
@pytest.mark.xfail(reason="N3 serializer randomly omits triple")
def test():
graph1 = rdflib.Graph()
graph1.parse(data=test_n3, format="n3")
"""
>>> sorted(list(graph1))
[
(
rdflib.term.BNode('fde0470d85a044b6780f0c6804b119063b1'),
rdflib.term.URIRef('http://www.w3.org/1999/02/22-rdf-syntax-ns#type'),
rdflib.term.URIRef('http://www.w3.org/2000/01/rdf-schema#Class')
),
(
rdflib.term.URIRef('http://test/a'),
rdflib.term.URIRef('http://test/d'),
rdflib.term.URIRef('http://test/c')
),
(
<Graph identifier=_:Formula2 (<class 'rdflib.graph.QuotedGraph'>)>,
rdflib.term.URIRef('http://www.w3.org/2000/10/swap/log#implies'),
<Graph identifier=_:Formula3 (<class 'rdflib.graph.QuotedGraph'>)>
)
]
"""
graph2 = rdflib.Graph()
graph2.parse(data=graph1.serialize(format="n3"), format="n3")
assert (
rdflib.term.URIRef('http://test/a'),
rdflib.term.URIRef('http://test/d'),
rdflib.term.URIRef('http://test/c')
) in graph2Sample run_test.py results ...
(rdflib) $ ./run_tests.py test/test_n3_formula.py
Running pytest with: ["test/test_n3_formula.py"]
============================================ test session starts =============================================
platform linux -- Python 3.8.10, pytest-6.2.5, py-1.11.0, pluggy-1.0.0
rootdir: rdflib, configfile: tox.ini
plugins: subtests-0.6.0, cov-3.0.0
collected 1 item
test/test_n3_formula.py::test XFAIL (N3 serializer randomly omits triple) [100%]
============================================= 1 xfailed in 0.02s =============================================
(rdflib) $ ./run_tests.py test/test_n3_formula.py
Running pytest with: ["test/test_n3_formula.py"]
============================================ test session starts =============================================
platform linux -- Python 3.8.10, pytest-6.2.5, py-1.11.0, pluggy-1.0.0
rootdir: rdflib, configfile: tox.ini
plugins: subtests-0.6.0, cov-3.0.0
collected 1 item
test/test_n3_formula.py::test XPASS (N3 serializer randomly omits triple) [100%]
============================================= 1 xpassed in 0.01s =============================================