fix: make rdflib.term.Node abstract (fixes #2518)

rdflib/collection.py

@@ -82,8 +82,7 @@ def n3(self) -> str:
           "2"^^<http://www.w3.org/2001/XMLSchema#integer>
           "3"^^<http://www.w3.org/2001/XMLSchema#integer> )
         """
-        # type error: "Node" has no attribute "n3"
-        return "( %s )" % (" ".join([i.n3() for i in self]))  # type: ignore[attr-defined]
+        return "( %s )" % (" ".join([i.n3() for i in self]))
 
     def _get_container(self, index: int) -> Optional[Node]:
         """Gets the first, rest holding node at index."""

rdflib/graph.py

@@ -1609,10 +1609,9 @@ def update(
 
         return processor.update(update_object, initBindings, initNs, **kwargs)
 
-    def n3(self) -> str:
+    def n3(self, namespace_manager: Optional["NamespaceManager"] = None) -> str:
         """Return an n3 identifier for the Graph"""
-        # type error: "IdentifiedNode" has no attribute "n3"
-        return "[%s]" % self.identifier.n3()  # type: ignore[attr-defined]
+        return "[%s]" % self.identifier.n3(namespace_manager=namespace_manager)
 
     def __reduce__(self) -> Tuple[Type[Graph], Tuple[Store, _ContextIdentifierType]]:
         return (
@@ -2591,14 +2590,12 @@ def addN(self: _GraphT, quads: Iterable["_QuadType"]) -> _GraphT:  # noqa: N802
         )
         return self
 
-    def n3(self) -> str:
+    def n3(self, namespace_manager: Optional["NamespaceManager"] = None) -> str:
         """Return an n3 identifier for the Graph"""
-        # type error: "IdentifiedNode" has no attribute "n3"
-        return "{%s}" % self.identifier.n3()  # type: ignore[attr-defined]
+        return "{%s}" % self.identifier.n3(namespace_manager=namespace_manager)
 
     def __str__(self) -> str:
-        # type error: "IdentifiedNode" has no attribute "n3"
-        identifier = self.identifier.n3()  # type: ignore[attr-defined]
+        identifier = self.identifier.n3()
         label = self.store.__class__.__name__
         pattern = (
             "{this rdflib.identifier %s;rdflib:storage "
@@ -2900,7 +2897,7 @@ def parse(  # type: ignore[override]
     ) -> NoReturn:  # noqa: N803
         raise ModificationException()
 
-    def n3(self) -> NoReturn:
+    def n3(self, namespace_manager: Optional["NamespaceManager"] = None) -> NoReturn:
         raise UnSupportedAggregateOperation()
 
     def __reduce__(self) -> NoReturn:

rdflib/plugins/serializers/nt.py

@@ -60,14 +60,12 @@ def __init__(self, store: Graph):
 def _nt_row(triple: _TripleType) -> str:
     if isinstance(triple[2], Literal):
         return "%s %s %s .\n" % (
-            # type error: "Node" has no attribute "n3"
-            triple[0].n3(),  # type: ignore[attr-defined]
-            triple[1].n3(),  # type: ignore[attr-defined]
+            triple[0].n3(),
+            triple[1].n3(),
             _quoteLiteral(triple[2]),
         )
     else:
-        # type error: "Node" has no attribute "n3"
-        return "%s %s %s .\n" % (triple[0].n3(), triple[1].n3(), triple[2].n3())  # type: ignore[attr-defined]
+        return "%s %s %s .\n" % (triple[0].n3(), triple[1].n3(), triple[2].n3())
 
 
 def _quoteLiteral(l_: Literal) -> str:  # noqa: N802

rdflib/plugins/serializers/trig.py

@@ -101,8 +101,7 @@ def serialize(
                     # Show the full graph URI if a prefix for it doesn't already exist
                     iri = self.getQName(store.identifier, False)
                     if iri is None:
-                        # type error: "IdentifiedNode" has no attribute "n3"
-                        iri = store.identifier.n3()  # type: ignore[attr-defined]
+                        iri = store.identifier.n3()
                 self.write(self.indent() + "\n%s {" % iri)
 
             self.depth += 1

rdflib/plugins/sparql/algebra.py

@@ -1006,12 +1006,10 @@ def convert_node_arg(
     ) -> str:
         if isinstance(node_arg, Identifier):
             if node_arg in self.aggr_vars.keys():
-                # type error: "Identifier" has no attribute "n3"
-                grp_var = self.aggr_vars[node_arg].pop(0).n3()  # type: ignore[attr-defined]
+                grp_var = self.aggr_vars[node_arg].pop(0).n3()
                 return grp_var
             else:
-                # type error: "Identifier" has no attribute "n3"
-                return node_arg.n3()  # type: ignore[attr-defined]
+                return node_arg.n3()
         elif isinstance(node_arg, CompValue):
             return "{" + node_arg.name + "}"
         elif isinstance(node_arg, Expr):

rdflib/plugins/stores/sparqlstore.py

@@ -61,8 +61,7 @@ def _node_to_sparql(node: "Node") -> str:
             "SPARQLStore does not support BNodes! "
             "See http://www.w3.org/TR/sparql11-query/#BGPsparqlBNodes"
         )
-    # type error: "Node" has no attribute "n3"
-    return node.n3()  # type: ignore[attr-defined]
+    return node.n3()
 
 
 class SPARQLStore(SPARQLConnector, Store):

rdflib/term.py

@@ -20,6 +20,7 @@
 * Numerical Ranges
 
 """
+import abc
 import re
 from fractions import Fraction
 
@@ -128,13 +129,17 @@ def _is_valid_unicode(value: Union[str, bytes]) -> bool:
     return True
 
 
-class Node:
+class Node(abc.ABC):
     """
     A Node in the Graph.
     """
 
     __slots__ = ()
 
+    @abc.abstractmethod
+    def n3(self, namespace_manager: Optional["NamespaceManager"] = None) -> str:
+        ...
+
 
 class Identifier(Node, str):  # allow Identifiers to be Nodes in the Graph
     """

test/utils/dawg_manifest.py

@@ -46,12 +46,12 @@ class ManifestEntry:
     result_cardinality: Optional[URIRef] = field(init=False)
 
     def __post_init__(self) -> None:
-        type = self.value(RDF.type, IdentifiedNode)
+        type = self.value(RDF.type, IdentifiedNode)  # type: ignore[type-abstract]
         assert type is not None
         self.type = type
 
-        self.action = self.value(MF.action, IdentifiedNode)
-        self.result = self.value(MF.result, IdentifiedNode)
+        self.action = self.value(MF.action, IdentifiedNode)  # type: ignore[type-abstract]
+        self.result = self.value(MF.result, IdentifiedNode)  # type: ignore[type-abstract]
         self.result_cardinality = self.value(MF.resultCardinality, URIRef)
         if self.result_cardinality is not None:
             assert self.result_cardinality == MF.LaxCardinality