Implement RDF Patch serializer (#2877)

* Implement RDF Patch serializer. Supports serialization from Dataset instances only; triples and quads within a Dataset are supported.

* Add examples for Patch serialization.

* Remove unnecessary use of addN -> add

* Handle RDFLib graph/dataset addition quirks. Should fix static analysis issues.

* Fix mypy errors

* Attempt to fix failing test.

* Add Patch documentation + docstring

---------

Co-authored-by: Ashley Sommer <[email protected]>

docs/plugin_serializers.rst

@@ -21,6 +21,7 @@ n3         :class:`~rdflib.plugins.serializers.n3.N3Serializer`
 nquads     :class:`~rdflib.plugins.serializers.nquads.NQuadsSerializer`
 nt         :class:`~rdflib.plugins.serializers.nt.NTSerializer`
 hext       :class:`~rdflib.plugins.serializers.hext.HextuplesSerializer`
+patch      :class:`~rdflib.plugins.serializers.patch.PatchSerializer`
 pretty-xml :class:`~rdflib.plugins.serializers.rdfxml.PrettyXMLSerializer`
 trig       :class:`~rdflib.plugins.serializers.trig.TrigSerializer`
 trix       :class:`~rdflib.plugins.serializers.trix.TriXSerializer`
@@ -34,6 +35,11 @@ JSON-LD
 -------
 JSON-LD - 'json-ld' - has been incorporated into RDFLib since v6.0.0.
 
+RDF Patch
+---------
+
+The RDF Patch Serializer - 'patch' - uses the RDF Patch format defined at https://afs.github.io/rdf-patch/. It supports serializing context aware stores as either addition or deletion patches; and also supports serializing the difference between two context aware stores as a Patch of additions and deletions.
+
 HexTuples
 ---------
 The HexTuples Serializer - 'hext' - uses the HexTuples format defined at https://github.com/ontola/hextuples.

examples/patch_serializer_example.py

@@ -0,0 +1,64 @@
+from rdflib import Dataset, Graph, Literal, URIRef
+
+
+def main():
+    # example for adding a quad
+    ds = Dataset()
+    g = Graph(identifier=URIRef("http://graph-a"))
+    ds.add_graph(g)
+    triple = (URIRef("http://subj-a"), URIRef("http://pred-a"), Literal("obj-a"))
+    ds.get_context(g.identifier).add(triple)
+    result = ds.serialize(format="patch", operation="add")
+    print("Add Quad Patch:")
+    print(result)
+
+    # alternate example for adding a quad
+    ds = Dataset()
+    quad = (
+        URIRef("http://subj-a"),
+        URIRef("http://pred-a"),
+        Literal("obj-a"),
+        Graph(identifier=URIRef("http://graph-a")),
+    )
+    ds.add(quad)
+    result = ds.serialize(format="patch", operation="add")
+    print("Add Quad Patch:")
+    print(result)
+
+    # example for adding a triple
+    ds = Dataset()
+    ds.add(triple)
+    result = ds.serialize(format="patch", operation="add")
+    print("\nAdd Triple Patch:")
+    print(result)
+
+    # Example for diff quads
+    quad_1 = (
+        URIRef("http://subj-a"),
+        URIRef("http://pred-a"),
+        Literal("obj-a"),
+        Graph(identifier=URIRef("http://graph-a")),
+    )
+    quad_2 = (
+        URIRef("http://subj-b"),
+        URIRef("http://pred-b"),
+        Literal("obj-b"),
+        Graph(identifier=URIRef("http://graph-b")),
+    )
+    quad_3 = (
+        URIRef("http://subj-c"),
+        URIRef("http://pred-c"),
+        Literal("obj-c"),
+        Graph(identifier=URIRef("http://graph-c")),
+    )
+    ds1 = Dataset()
+    ds2 = Dataset()
+    ds1.addN([quad_1, quad_2])
+    ds2.addN([quad_2, quad_3])
+    result = ds1.serialize(format="patch", target=ds2)
+    print("Diff Quad Patch:")
+    print(result)
+
+
+if __name__ == "__main__":
+    main()

rdflib/plugin.py

@@ -363,6 +363,12 @@ def plugins(
     "rdflib.plugins.serializers.hext",
     "HextuplesSerializer",
 )
+register(
+    "patch",
+    Serializer,
+    "rdflib.plugins.serializers.patch",
+    "PatchSerializer",
+)
 
 # Register Triple Parsers
 register(

rdflib/plugins/serializers/patch.py

@@ -0,0 +1,105 @@
+from __future__ import annotations
+
+import warnings
+from typing import IO, Optional
+from uuid import uuid4
+
+from rdflib import Dataset
+from rdflib.plugins.serializers.nquads import _nq_row
+from rdflib.plugins.serializers.nt import _nt_row
+from rdflib.serializer import Serializer
+
+add_remove_methods = {"add": "A", "remove": "D"}
+
+
+class PatchSerializer(Serializer):
+    """
+    Creates an RDF patch file to add and remove triples/quads.
+    Can either:
+    - Create an add or delete patch for a single Dataset.
+    - Create a patch to represent the difference between two Datasets.
+    """
+
+    def __init__(
+        self,
+        store: Dataset,
+    ):
+        self.store: Dataset = store
+        super().__init__(store)
+
+    def serialize(
+        self,
+        stream: IO[bytes],
+        base: Optional[str] = None,
+        encoding: Optional[str] = None,
+        **kwargs,
+    ):
+        """
+        Serialize the store to the given stream.
+        :param stream: The stream to serialize to.
+        :param base: The base URI to use for the serialization.
+        :param encoding: The encoding to use for the serialization.
+        :param kwargs: Additional keyword arguments.
+        Supported keyword arguments:
+        - operation: The operation to perform. Either 'add' or 'remove'.
+        - target: The target Dataset to compare against.
+        NB: Only one of 'operation' or 'target' should be provided.
+        - header_id: The header ID to use.
+        - header_prev: The previous header ID to use.
+        """
+        operation = kwargs.get("operation")
+        target = kwargs.get("target")
+        header_id = kwargs.get("header_id")
+        header_prev = kwargs.get("header_prev")
+        if not header_id:
+            header_id = f"uuid:{uuid4()}"
+        encoding = self.encoding
+        if base is not None:
+            warnings.warn("PatchSerializer does not support base.")
+        if encoding is not None and encoding.lower() != self.encoding.lower():
+            warnings.warn(
+                "PatchSerializer does not use custom encoding. "
+                f"Given encoding was: {encoding}"
+            )
+
+        def write_header():
+            stream.write(f"H id <{header_id}> .\n".encode(encoding, "replace"))
+            if header_prev:
+                stream.write(f"H prev <{header_prev}>\n".encode(encoding, "replace"))
+            stream.write("TX .\n".encode(encoding, "replace"))
+
+        def write_triples(contexts, op_code, use_passed_contexts=False):
+            for context in contexts:
+                if not use_passed_contexts:
+                    context = self.store.get_context(context.identifier)
+                for triple in context:
+                    stream.write(
+                        self._patch_row(triple, context.identifier, op_code).encode(
+                            encoding, "replace"
+                        )
+                    )
+
+        if operation:
+            assert operation in add_remove_methods, f"Invalid operation: {operation}"
+
+        write_header()
+        if operation:
+            operation_code = add_remove_methods.get(operation)
+            write_triples(self.store.contexts(), operation_code)
+        elif target:
+            to_add, to_remove = self._diff(target)
+            write_triples(to_add.contexts(), "A", use_passed_contexts=True)
+            write_triples(to_remove.contexts(), "D", use_passed_contexts=True)
+
+        stream.write("TC .\n".encode(encoding, "replace"))
+
+    def _diff(self, target):
+        rows_to_add = target - self.store
+        rows_to_remove = self.store - target
+        return rows_to_add, rows_to_remove
+
+    def _patch_row(self, triple, context_id, operation):
+        if context_id == self.store.default_context.identifier:
+            return f"{operation} {_nt_row(triple)}"
+        else:
+            return f"{operation} {_nq_row(triple, context_id)}"

test/test_serializers/test_serializer_patch.py

@@ -0,0 +1,178 @@
+from rdflib import Dataset, Graph, Literal, URIRef
+
+
+def test_add_quad():
+    ds = Dataset()
+    ds.add(
+        (
+            URIRef("http://example.org/subject1"),
+            URIRef("http://example.org/predicate2"),
+            Literal("object2"),
+            Graph(identifier=URIRef("http://example.org/graph1")),
+        )
+    )
+    result = ds.serialize(format="patch", operation="add")
+    assert (
+        """A <http://example.org/subject1> <http://example.org/predicate2> "object2" <http://example.org/graph1> .
+"""
+        in result
+    )
+
+
+def test_delete_quad():
+    ds = Dataset()
+    ds.add(
+        (
+            URIRef("http://example.org/subject1"),
+            URIRef("http://example.org/predicate2"),
+            Literal("object2"),
+            Graph(identifier=URIRef("http://example.org/graph1")),
+        )
+    )
+    result = ds.serialize(format="patch", operation="remove")
+    assert (
+        """D <http://example.org/subject1> <http://example.org/predicate2> "object2" <http://example.org/graph1> .
+"""
+        in result
+    )
+
+
+def test_diff_quad():
+    quad_1 = (
+        URIRef("http://example.org/subject1"),
+        URIRef("http://example.org/predicate2"),
+        Literal("object2"),
+        Graph(identifier=URIRef("http://example.org/graph1")),
+    )
+    quad_2 = (
+        URIRef("http://example.org/subject2"),
+        URIRef("http://example.org/predicate3"),
+        Literal("object3"),
+        Graph(identifier=URIRef("http://example.org/graph2")),
+    )
+    ds1 = Dataset()
+    ds2 = Dataset()
+    ds1.add(quad_1)
+    ds2.addN([quad_1, quad_2])
+    result = ds1.serialize(format="patch", target=ds2)
+    assert (
+        """A <http://example.org/subject2> <http://example.org/predicate3> "object3" <http://example.org/graph2> ."""
+        in result
+    )
+
+
+def test_add_triple():
+    ds = Dataset()
+    ds.add(
+        (
+            URIRef("http://example.org/subject1"),
+            URIRef("http://example.org/predicate2"),
+            Literal("object2"),
+        )
+    )
+    result = ds.serialize(format="patch", operation="add")
+    assert (
+        """A <http://example.org/subject1> <http://example.org/predicate2> "object2" ."""
+        in result
+    )
+
+
+def test_delete_triple():
+    ds = Dataset()
+    ds.add(
+        (
+            URIRef("http://example.org/subject1"),
+            URIRef("http://example.org/predicate2"),
+            Literal("object2"),
+        )
+    )
+    result = ds.serialize(format="patch", operation="remove")
+    assert (
+        """D <http://example.org/subject1> <http://example.org/predicate2> "object2" ."""
+        in result
+    )
+
+
+def test_diff_triple():
+    triple_1 = (
+        URIRef("http://example.org/subject1"),
+        URIRef("http://example.org/predicate2"),
+        Literal("object2"),
+    )
+    triple_2 = (
+        URIRef("http://example.org/subject2"),
+        URIRef("http://example.org/predicate3"),
+        Literal("object3"),
+    )
+    ds1 = Dataset()
+    ds2 = Dataset()
+    ds1.add(triple_1)
+    ds2.add(triple_1)
+    ds2.add(triple_2)
+    result = ds1.serialize(format="patch", target=ds2)
+    assert (
+        """A <http://example.org/subject2> <http://example.org/predicate3> "object3" ."""
+        in result
+    )
+
+
+def test_diff_quad_overlap():
+    quad_1 = (
+        URIRef("http://example.org/subject1"),
+        URIRef("http://example.org/predicate1"),
+        Literal("object1"),
+        Graph(identifier=URIRef("http://example.org/graph1")),
+    )
+    quad_2 = (
+        URIRef("http://example.org/subject2"),
+        URIRef("http://example.org/predicate2"),
+        Literal("object2"),
+        Graph(identifier=URIRef("http://example.org/graph2")),
+    )
+    quad_3 = (
+        URIRef("http://example.org/subject3"),
+        URIRef("http://example.org/predicate3"),
+        Literal("object3"),
+        Graph(identifier=URIRef("http://example.org/graph3")),
+    )
+    ds1 = Dataset()
+    ds2 = Dataset()
+    ds1.addN([quad_1, quad_2])
+    ds2.addN([quad_2, quad_3])
+    result = ds1.serialize(format="patch", target=ds2)
+    # first quad needs to be removed
+    assert (
+        """D <http://example.org/subject1> <http://example.org/predicate1> "object1" <http://example.org/graph1> ."""
+        in result
+    )
+    # third quad needs to be added
+    assert (
+        """A <http://example.org/subject3> <http://example.org/predicate3> "object3" <http://example.org/graph3> ."""
+        in result
+    )
+
+
+def test_header_id():
+    ds = Dataset()
+    ds.add(
+        (
+            URIRef("http://example.org/subject1"),
+            URIRef("http://example.org/predicate2"),
+            Literal("object2"),
+        )
+    )
+    result = ds.serialize(format="patch", operation="add", header_id="uuid:123")
+    assert """H id <uuid:123>""" in result
+
+
+def test_prev_header():
+    ds = Dataset()
+    ds.add(
+        (
+            URIRef("http://example.org/subject1"),
+            URIRef("http://example.org/predicate2"),
+            Literal("object2"),
+        )
+    )
+    result = ds.serialize(format="patch", operation="add", header_prev="uuid:123")
+    assert """H prev <uuid:123>""" in result