fix: raise an exception when serialization format does not support quads

- fixes <#2393>

rdflib/util.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import logging
+
 """
 Some utility functions.
 
@@ -614,3 +616,31 @@ def _iri2uri(iri: str) -> str:
         uri += "#"
 
     return uri
+
+
+def _has_non_default_graphs(graph: rdflib.graph.ConjunctiveGraph) -> bool:
+    """
+    Check if the value passed as `graph` contains graphs other than the default
+    graph.
+
+    The intent of this is to detect if the value passed can be serialized using
+    formats which do not support named graphs like N-Triples and Turtle.
+
+    Ideally this function would check if the supplied value contains any named
+    graphs, but RDFLib assigns a name to the default graph, so the best that can
+    be done is to check if the supplied graph contains any graphs other than the
+    default graph.
+
+    If the supplied value contains only the default graph and other graphs, this
+    function will return `False`, otherwise if the value passed contains at
+    least one graph other than the default graph it will return `True`.
+    """
+    default_context = graph.default_context
+    logging.debug("default_context.identifier = %s", default_context.identifier)
+    for context_index, context in enumerate(graph.contexts()):
+        logging.debug("contexts[%s].identifier = %s", context_index, context.identifier)
+        if context.identifier != default_context.identifier:
+            return True
+        if context_index > 0:
+            return True
+    return False

setup.cfg

@@ -14,7 +14,6 @@ exclude =
     test/data/suites/, # does not contain python
     test/jsonld/1.1/, # does not contain python
     test/jsonld/test-suite/, # does not contain python
-    test/data/variants/, # does not contain python
     test/data/translate_algebra/, # does not contain python
     docs/rdf_terms.rst, # This file is causing an error on GitHub actions
 extend-ignore =

test/data.py → test/data/__init__.py

@@ -3,7 +3,7 @@
 from rdflib import URIRef
 from rdflib.graph import Graph
 
-TEST_DIR = Path(__file__).parent
+TEST_DIR = Path(__file__).parent.parent
 TEST_DATA_DIR = TEST_DIR / "data"
 
 alice_uri = URIRef("http://example.org/alice")
@@ -22,7 +22,7 @@
 context2 = URIRef("urn:example:context-2")
 
 
-simple_triple_graph = Graph().add(
+SIMPLE_TRIPLE_GRAPH = Graph().add(
     (
         URIRef("http://example.org/subject"),
         URIRef("http://example.org/predicate"),

test/data/variants/README.md

@@ -1,12 +1,12 @@
 # multi variant graphs
 
-This directory containts variants of the same graph encoded in different
+This directory contains variants of the same graph encoded in different
 formats, or differently in the same format.
 
-The graph that a specific file is a variant of is determined by it's filename.
-Files that differ only in file extention but have the same basename are
+The graph that a specific file is a variant of is determined by its filename.
+Files that differ only in file extensions but have the same basename are
 considered variants of the same graph. Additionally, any suffix that matches
-`-variant-[^/]*` is excluded when determening the graph key, so the following
+`-variant-[^/]*` is excluded when determining the graph key, so the following
 files are all considered variants of the same graph:
 
 ```

test/data/variants/diverse_quads.py

@@ -0,0 +1,29 @@
+from test.utils.namespace import EGDC, EGSCHEME, EGURN
+
+from rdflib.graph import ConjunctiveGraph, Graph
+from rdflib.namespace import XSD
+from rdflib.term import Literal
+
+
+def populate_graph(graph: Graph) -> None:
+    assert isinstance(graph, ConjunctiveGraph)
+
+    graph.add((EGSCHEME.subject, EGSCHEME.predicate, EGSCHEME.object))
+    graph.add((EGDC.subject, EGDC.predicate, Literal("typeless")))
+    graph.add((EGURN.subject, EGURN.predicate, EGURN.object))
+
+    egscheme_graph = graph.get_context(EGSCHEME.graph)
+    egscheme_graph.add((EGDC.subject, EGDC.predicate, Literal("日本語の表記体系", lang="jpx")))
+    egscheme_graph.add((EGURN.subject, EGSCHEME.predicate, EGSCHEME.subject))
+    egscheme_graph.add((EGSCHEME.subject, EGSCHEME.predicate, EGSCHEME.object))
+    egscheme_graph.add((EGSCHEME.subject, EGSCHEME.predicate, Literal(12)))
+
+    egurn_graph = graph.get_context(EGURN.graph)
+    egurn_graph.add((EGSCHEME.subject, EGSCHEME.predicate, EGSCHEME.object))
+    egurn_graph.add((EGSCHEME.subject, EGDC.predicate, EGDC.object))
+    egurn_graph.add(
+        (EGSCHEME.subject, EGDC.predicate, Literal("XSD string", datatype=XSD.string))
+    )
+
+
+__all__ = ["populate_graph"]

test/data/variants/diverse_triples.nq

@@ -0,0 +1,5 @@
+<http://example.com/subject> <http://example.com/predicate> "日本語の表記体系"@jpx .
+<urn:example:subject> <example:predicate> <example:subject> .
+<example:object> <http://example.com/predicate> "XSD string" .
+<example:subject> <example:predicate> <example:object> .
+<example:subject> <example:predicate> "12"^^<http://www.w3.org/2001/XMLSchema#integer> .

test/data/variants/diverse_triples.py

@@ -0,0 +1,18 @@
+from test.utils.namespace import EGDC, EGSCHEME, EGURN
+
+from rdflib.graph import ConjunctiveGraph, Graph
+from rdflib.namespace import XSD
+from rdflib.term import Literal
+
+
+def populate_graph(graph: Graph) -> None:
+    assert isinstance(graph, Graph)
+
+    graph.add((EGDC.subject, EGDC.predicate, Literal("日本語の表記体系", lang="jpx")))
+    graph.add((EGURN.subject, EGSCHEME.predicate, EGSCHEME.subject))
+
+    graph.add((EGSCHEME.object, EGDC.predicate, Literal("XSD string")))
+    graph.add((EGSCHEME.subject, EGSCHEME.predicate, EGSCHEME.object))
+    graph.add((EGSCHEME.subject, EGSCHEME.predicate, Literal(12)))
+
+__all__ = ["populate_graph"]

test/data/variants/diverse_triples.trig

@@ -0,0 +1,15 @@
+@prefix eghttp: <http://example.com/> .
+@prefix egurn: <urn:example:> .
+@prefix egschema: <example:> .
+@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
+
+{
+    eghttp:subject eghttp:predicate "日本語の表記体系"@jpx .
+
+    egurn:subject egschema:predicate egschema:subject .
+}
+
+egschema:object eghttp:predicate "XSD string"^^xsd:string .
+
+egschema:subject egschema:predicate egschema:object,
+        12 .

test/data/variants/simple_quad.py

@@ -0,0 +1,13 @@
+from test.utils.namespace import EGDO
+
+from rdflib.graph import ConjunctiveGraph, Graph
+
+
+def populate_graph(graph: Graph) -> None:
+    assert isinstance(graph, ConjunctiveGraph)
+
+    egdo_graph = graph.get_context(EGDO.graph)
+    egdo_graph.add((EGDO.subject, EGDO.predicate, EGDO.object))
+
+
+__all__ = ["populate_graph"]

test/data/variants/simple_triple.py

@@ -0,0 +1,10 @@
+from test.utils.namespace import EGDO
+
+from rdflib.graph import Graph
+
+
+def populate_graph(graph: Graph) -> None:
+    graph.add((EGDO.subject, EGDO.predicate, EGDO.object))
+
+
+__all__ = ["populate_graph"]

test/data/variants/simple_triple.trig

@@ -0,0 +1,2 @@
+<http://example.org/subject>
+        <http://example.org/predicate>  <http://example.org/object> .

test/test_graph/test_graph_redirect.py

@@ -1,12 +1,15 @@
-from test.data import TEST_DATA_DIR, simple_triple_graph
+from test.data import TEST_DATA_DIR
 from test.utils import GraphHelper
 from test.utils.http import MethodName, MockHTTPResponse
 from test.utils.httpservermock import ServedBaseHTTPServerMock
+from test.utils.variants import load_pyvariant
 from typing import Tuple
 from urllib.parse import urlparse
 
 from rdflib.graph import Graph
 
+SIMPLE_TRIPLE_GRAPH = load_pyvariant("simple_triple", Graph)
+
 
 def test_graph_redirect_new_host(
     function_httpmocks: Tuple[ServedBaseHTTPServerMock, ServedBaseHTTPServerMock]
@@ -38,7 +41,7 @@ def test_graph_redirect_new_host(
 
     graph = Graph()
     graph.parse(location=f"{mock_a.url}/a/data.ttl")
-    GraphHelper.assert_sets_equals(graph, simple_triple_graph)
+    GraphHelper.assert_sets_equals(graph, SIMPLE_TRIPLE_GRAPH)
     for mock in function_httpmocks:
         assert 1 == len(mock.requests[MethodName.GET])
         for request in mock.requests[MethodName.GET]:

test/test_graph/test_variants.py

@@ -5,9 +5,11 @@
 import os
 import re
 from dataclasses import dataclass, field
+from importlib import import_module
 from pathlib import Path, PurePath
 from test.data import TEST_DATA_DIR
 from test.utils import GraphHelper
+from test.utils.graph import load_sources
 from typing import (
     ClassVar,
     Collection,
@@ -27,11 +29,13 @@
 
 import rdflib.compare
 import rdflib.util
-from rdflib.graph import ConjunctiveGraph
+from rdflib.graph import ConjunctiveGraph, Graph
 from rdflib.namespace import XSD
 from rdflib.term import URIRef
 from rdflib.util import guess_format
 
+MODULE_PATH = Path(__file__).parent
+
 TEST_DIR = Path(__file__).parent.parent.absolute()
 VARIANTS_DIR = TEST_DATA_DIR / "variants"
 
@@ -86,11 +90,27 @@ class GraphVariants:
     key: str
     variants: Dict[str, Path] = field(default_factory=OrderedDict)
     asserts: GraphAsserts = field(default_factory=lambda: GraphAsserts())
+    pyvariant: Optional[Path] = None
 
     _variant_regex: ClassVar[Pattern[str]] = re.compile(
         r"^(.*?)(|[-]variant-[^/]+|[-]asserts)$"
     )
 
+    def parse_pyvariant(self, graph: Graph) -> None:
+        """
+        Load a graph from a Python file.
+        """
+        assert self.pyvariant is not None
+
+        relative_path = self.pyvariant.relative_to(MODULE_PATH.parent.parent)
+
+        logging.debug("relative_path = %s", relative_path)
+        module_name = ".".join([*relative_path.parts[:-1], relative_path.stem])
+        logging.debug("module_name = %s", module_name)
+        module = import_module(module_name)
+        logging.debug("module = %s", module)
+        module.populate_graph(graph)
+
     def pytest_param(
         self,
         marks: Optional[
@@ -123,13 +143,14 @@ def for_files(
         for file_path in file_paths:
             logging.debug("file_path = %s", file_path)
             file_key, variant_key = cls._decompose_path(file_path, basedir)
-            # file_key = f"{file_path.parent / stem}"
             if file_key not in graph_varaint_dict:
                 graph_variant = graph_varaint_dict[file_key] = GraphVariants(file_key)
             else:
                 graph_variant = graph_varaint_dict[file_key]
             if variant_key.endswith("-asserts.json"):
                 graph_variant.asserts = GraphAsserts.from_path(file_path)
+            elif variant_key.endswith(".py"):
+                graph_variant.pyvariant = file_path
             else:
                 graph_variant.variants[variant_key] = file_path
         return graph_varaint_dict
@@ -139,7 +160,9 @@ def for_directory(
         cls, directory: Path, basedir: Optional[Path] = None
     ) -> Dict[str, "GraphVariants"]:
         file_paths = []
-        for file_path in directory.glob("**/*"):
+        logging.debug("directory = %s, basedir = %s", directory, basedir)
+        for file_path in directory.glob("*"):
+            logging.debug("file_path = %s", file_path)
             if not file_path.is_file():
                 continue
             if file_path.name.endswith(".md"):
@@ -227,6 +250,13 @@ def test_variants(graph_variant: GraphVariants) -> None:
     first_path: Optional[Path] = None
     logging.debug("graph_variant.asserts = %s", graph_variant.asserts)
 
+    if graph_variant.pyvariant is not None:
+        first_path = graph_variant.pyvariant
+        logging.debug("loading pyvariant = %s", graph_variant.pyvariant)
+        first_graph = ConjunctiveGraph(identifier=public_id)
+        # graph_variant.parse_pyvariant(first_graph)
+        load_sources(first_path, graph=first_graph)
+
     for variant_key, variant_path in graph_variant.variants.items():
         logging.debug("variant_path = %s", variant_path)
         format = guess_format(variant_path.name, fmap=SUFFIX_FORMAT_MAP)

test/test_serializers/test_serialize_context_aware.py

@@ -0,0 +1,53 @@
+import itertools
+import logging
+from test.utils.graph import GRAPH_FORMATS, GraphType
+from test.utils.variants import load_pyvariant
+from typing import Dict, Iterable, Type
+
+import pytest
+from _pytest.mark.structures import ParameterSet
+from _pytest.outcomes import Failed
+
+from rdflib.graph import ConjunctiveGraph, Dataset, Graph
+
+
+def make_quads_in_triples_cases() -> Iterable[ParameterSet]:
+    """
+    Generate test cases for serializing named graphs (i.e. quads) into a format
+    that does not support named graphs.
+    """
+    triple_only_formats = [
+        graph_format
+        for graph_format in GRAPH_FORMATS
+        if graph_format.info.graph_types == {GraphType.TRIPLE}
+    ]
+    for graph_type, graph_format in itertools.product(
+        (ConjunctiveGraph, Dataset), triple_only_formats
+    ):
+        for serializer in graph_format.info.serializers:
+            yield pytest.param(
+                graph_type, serializer, marks=pytest.mark.xfail(raises=Failed)
+            )
+
+
+CONJUNCTIVE_GRAPH_WITH_QUADS = load_pyvariant("diverse_quads", ConjunctiveGraph)
+DATASET_WITH_QUADS = load_pyvariant("diverse_quads", Dataset)
+
+GRAPHS: Dict[Type[Graph], Graph] = {
+    ConjunctiveGraph: CONJUNCTIVE_GRAPH_WITH_QUADS,
+    Dataset: DATASET_WITH_QUADS,
+}
+
+
+@pytest.mark.parametrize(["graph_type", "serializer"], make_quads_in_triples_cases())
+def test_quads_in_triples(graph_type: Type[ConjunctiveGraph], serializer: str) -> None:
+    """
+    Serializing named graphs (i.e. quads) inside a `ConjunctiveGraph` into a
+    format that does not support named graphs should result in an exception.
+    """
+    graph = GRAPHS[graph_type]
+    assert type(graph) is graph_type
+    with pytest.raises(Exception) as caught:
+        graph.serialize(format=serializer)
+
+    logging.debug("caught.value = %r", caught.value, exc_info=caught.value)