fix: Add `to_dict` method to the JSON-LD `Context` class. (#2310)

`Context.to_dict` is used in JSON-LD serialization, but it was not implemented.
This change adds the method.

- Closes <https://github.com/RDFLib/rdflib/issues/2138>.

---------

Co-authored-by: Marc-Antoine Parent <maparent@acm.org>

2 files changed, 95 insertions, 0 deletions

diff --git a/test/jsonld/test_context.py b/test/jsonld/test_context.py
index 6578268a..034936d2 100644
--- a/test/jsonld/test_context.py
+++ b/test/jsonld/test_context.py
@@ -2,10 +2,12 @@
 JSON-LD Context Spec
 """
 
+import json
 from functools import wraps
 from pathlib import Path
 from typing import Any, Dict
 
+from rdflib.namespace import PROV, XSD, Namespace
 from rdflib.plugins.shared.jsonld import context, errors
 from rdflib.plugins.shared.jsonld.context import Context
 
@@ -234,3 +236,52 @@ def test_dict_source(tmp_path: Path) -> None:
     file.write_text(r"""{ "@context": { "ex": "http://example.com/" } }""")
     ctx = Context(source=[{"@context": file.as_uri()}])
     assert "http://example.com/" == ctx.terms["ex"].id
+
+
+EG = Namespace("https://example.com/")
+
+DIVERSE_CONTEXT = json.loads(
+    """
+        {
+            "@context": {
+                "ex": "https://example.com/",
+                "generatedAt": { "@id": "http://www.w3.org/ns/prov#generatedAtTime", "@type": "http://www.w3.org/2001/XMLSchema#dateTime" },
+                "graphMap": { "@id": "https://example.com/graphMap", "@container": ["@graph", "@id"] },
+                "occupation_en": { "@id": "https://example.com/occupation", "@language": "en" },
+                "children": { "@reverse": "https://example.com/parent" }
+            }
+        }
+        """
+)
+
+
+def test_parsing() -> None:
+    """
+    A `Context` can be parsed from a dict.
+    """
+    ctx = Context(DIVERSE_CONTEXT)
+    assert f"{EG}" == ctx.terms["ex"].id
+    assert f"{PROV.generatedAtTime}" == ctx.terms["generatedAt"].id
+    assert f"{XSD.dateTime}" == ctx.terms["generatedAt"].type
+    assert f"{EG.graphMap}" == ctx.terms["graphMap"].id
+    assert {"@graph", "@id"} == ctx.terms["graphMap"].container
+    assert f"{EG.occupation}" == ctx.terms["occupation_en"].id
+    assert "en" == ctx.terms["occupation_en"].language
+    assert False is ctx.terms["occupation_en"].reverse
+    assert True is ctx.terms["children"].reverse
+    assert f"{EG.parent}" == ctx.terms["children"].id
+
+
+def test_to_dict() -> None:
+    """
+    A `Context` can be converted to a dictionary.
+    """
+    ctx = Context()
+    ctx.add_term("ex", f"{EG}")
+    ctx.add_term("generatedAt", f"{PROV.generatedAtTime}", coercion=f"{XSD.dateTime}")
+    ctx.add_term("graphMap", f"{EG.graphMap}", container=["@graph", "@id"])
+    ctx.add_term("occupation_en", f"{EG.occupation}", language="en")
+    ctx.add_term("children", f"{EG.parent}", reverse=True)
+    result = ctx.to_dict()
+    result["graphMap"]["@container"] = sorted(result["graphMap"]["@container"])
+    assert DIVERSE_CONTEXT["@context"] == result
diff --git a/test/test_serializers/test_serializer_jsonld.py b/test/test_serializers/test_serializer_jsonld.py
new file mode 100644
index 00000000..aff0544e
--- /dev/null
+++ b/test/test_serializers/test_serializer_jsonld.py
@@ -0,0 +1,44 @@
+import json
+import logging
+import pprint
+from typing import Any, Dict, Union
+
+import pytest
+
+from rdflib import Graph
+from rdflib.namespace import Namespace
+from rdflib.plugins.shared.jsonld.context import Context
+
+EG = Namespace("http://example.org/")
+
+
+@pytest.mark.parametrize(
+    ["input"],
+    [
+        (
+            Context(
+                {
+                    "eg": f"{EG}",
+                }
+            ),
+        ),
+        ({"eg": f"{EG}"},),
+    ],
+)
+def test_serialize_context(input: Union[Dict[str, Any], Context]) -> None:
+    """
+    The JSON-LD serializer accepts and correctly serializes the context argument to the output.
+    """
+    graph = Graph()
+    graph.add((EG.subject, EG.predicate, EG.object0))
+    graph.add((EG.subject, EG.predicate, EG.object1))
+    context = Context(
+        {
+            "eg": f"{EG}",
+        }
+    )
+    logging.debug("context = %s", pprint.pformat(vars(context)))
+    data = graph.serialize(format="json-ld", context=context)
+    logging.debug("data = %s", data)
+    obj = json.loads(data)
+    assert obj["@context"] == {"eg": f"{EG}"}