From 5e86f661eeaabcd382919ad351298be53c829117 Mon Sep 17 00:00:00 2001
From: Edmond Chuc <edmond@kurrawong.ai>
Date: Mon, 20 Oct 2025 12:57:22 +1000
Subject: [PATCH] feat: add Dataset __iadd__ support

fixes: https://github.com/RDFLib/rdflib/issues/3031
---
 rdflib/graph.py                       |  6 ++
 test/test_dataset/test_dataset_add.py | 88 ++++++++++++++++++++++++++-
 test/test_sparql/test_initbindings.py |  5 +-
 3 files changed, 96 insertions(+), 3 deletions(-)

diff --git a/rdflib/graph.py b/rdflib/graph.py
index 5d739a9574..32b879bda2 100644
--- a/rdflib/graph.py
+++ b/rdflib/graph.py
@@ -2591,6 +2591,12 @@ def __setstate__(
         # type error: Property "identifier" defined in "Graph" is read-only
         self.store, self.identifier, self.default_graph, self.default_union = state  # type: ignore[misc]
 
+    def __iadd__(self: _DatasetT, other: Iterable[_QuadType]) -> _DatasetT:  # type: ignore[override, misc]
+        """Add all quads in Dataset other to Dataset.
+        BNode IDs are not changed."""
+        self.addN((s, p, o, g) for s, p, o, g in other)
+        return self
+
     def graph(
         self,
         identifier: Optional[Union[_ContextIdentifierType, _ContextType, str]] = None,
diff --git a/test/test_dataset/test_dataset_add.py b/test/test_dataset/test_dataset_add.py
index a3197ae2e2..3a56998ac3 100644
--- a/test/test_dataset/test_dataset_add.py
+++ b/test/test_dataset/test_dataset_add.py
@@ -1,4 +1,8 @@
-from rdflib import RDF, RDFS, Dataset, Graph, URIRef
+from textwrap import dedent
+
+from rdflib import RDF, RDFS, Dataset, Graph, Literal, URIRef
+from rdflib.compare import isomorphic
+from rdflib.graph import DATASET_DEFAULT_GRAPH_ID
 from test.data import TEST_DATA_DIR
 
 
@@ -99,3 +103,85 @@ def test_dataset_parse_return_value():
     )
     assert len(ds)
     assert return_value is ds
+
+
+def test_dataset_iadd():
+    ds = Dataset()
+    ds.add(
+        (
+            URIRef("https://example.com/subject"),
+            URIRef("https://example.com/p/predicate"),
+            Literal("object"),
+        )
+    )
+
+    ds2 = Dataset()
+    ds2.add(
+        (
+            URIRef("https://example.com/subject"),
+            URIRef("https://example.com/p/predicate"),
+            Literal("object"),
+            URIRef("https://example.com/graph"),
+        )
+    )
+
+    data = """
+    {
+        <https://example.com/subject2> <https://example.com/p/predicate2> "object2" .
+    }
+
+    <https://example.com/graph> {
+        <https://example.com/subject-other> <https://example.com/p/predicate-other> "Triple-Other" .
+    }
+
+    <https://example.com/graph2> {
+        <https://example.com/subject-y> <https://example.com/predicate-y> "Triple Y" .
+    }
+
+    """
+    ds3 = Dataset().parse(data=data, format="trig")
+
+    # Combine the datasets
+    ds += ds2 + ds3
+
+    expected_default_graph_data = dedent(
+        """
+        @prefix ns2: <https://example.com/> .
+        @prefix ns3: <https://example.com/p/> .
+        ns2:subject2 ns3:predicate2 "object2" .
+        ns2:subject ns3:predicate "object" .
+    """
+    )
+    expected_default_graph = Graph(identifier=DATASET_DEFAULT_GRAPH_ID).parse(
+        data=expected_default_graph_data, format="turtle"
+    )
+
+    expected_graph1_data = dedent(
+        """
+        @prefix ns2: <https://example.com/> .
+        @prefix ns3: <https://example.com/p/> .
+        ns2:subject ns3:predicate "object" .
+        ns2:subject-other ns3:predicate-other "Triple-Other" .
+    """
+    )
+    expected_graph1 = Graph(identifier=URIRef("https://example.com/graph")).parse(
+        data=expected_graph1_data, format="turtle"
+    )
+
+    expected_graph2 = dedent(
+        """
+        @prefix ns2: <https://example.com/> .
+        ns2:subject-y ns2:predicate-y "Triple Y" .
+    """
+    )
+    expected_graph2 = Graph(identifier=URIRef("https://example.com/graph2")).parse(
+        data=expected_graph2, format="turtle"
+    )
+
+    assert isomorphic(expected_default_graph, ds.default_graph)
+    assert isomorphic(
+        expected_graph1, ds.get_graph(URIRef("https://example.com/graph"))
+    )
+    assert isomorphic(
+        expected_graph2, ds.get_graph(URIRef("https://example.com/graph2"))
+    )
diff --git a/test/test_sparql/test_initbindings.py b/test/test_sparql/test_initbindings.py
index 55f5853a3c..58aa8d6177 100644
--- a/test/test_sparql/test_initbindings.py
+++ b/test/test_sparql/test_initbindings.py
@@ -1,4 +1,5 @@
 from rdflib import Dataset, Literal, URIRef, Variable
+from rdflib.graph import DATASET_DEFAULT_GRAPH_ID
 from rdflib.plugins.sparql import prepareQuery
 from test.utils.namespace import EGDC
 
@@ -274,8 +275,8 @@ def test_prepare():
 def test_data():
     data = Dataset()
     data += [
-        (URIRef("urn:a"), URIRef("urn:p"), Literal("a")),
-        (URIRef("urn:b"), URIRef("urn:p"), Literal("b")),
+        (URIRef("urn:a"), URIRef("urn:p"), Literal("a"), DATASET_DEFAULT_GRAPH_ID),
+        (URIRef("urn:b"), URIRef("urn:p"), Literal("b"), DATASET_DEFAULT_GRAPH_ID),
     ]
 
     a = set(