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

- fixes <#2393>

Author: aucampia

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 renamed to 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"]