Track base URI changes while resolving pointers.

Author: Julian

referencing/_core.py

@@ -165,6 +165,12 @@ def pointer(self, pointer: str, resolver: Resolver[D]) -> Resolved[D]:
                 contents = contents[segment]  # type: ignore[reportUnknownArgumentType]  # noqa: E501
             except LookupError:
                 raise exceptions.PointerToNowhere(ref=pointer, resource=self)
+
+            # FIXME: this is slightly wrong, we need to know that we are
+            #        entering a subresource specifically, not just any mapping
+            if not isinstance(contents, Sequence):
+                subresource = self._specification.create_resource(contents)  # type: ignore[reportUnknownArgumentType]  # noqa: E501
+                resolver = resolver.in_subresource(subresource)
         return Resolved(contents=contents, resolver=resolver)  # type: ignore[reportUnknownArgumentType]  # noqa: E501
 
 

referencing/tests/test_core.py

@@ -503,6 +503,31 @@ def test_in_subresource(self):
         second = sub.lookup("grandchild")
         assert second.contents == {"ID": "grandchild"}
 
+    def test_in_pointer_subresource(self):
+        root = ID_AND_CHILDREN.create_resource(
+            {
+                "ID": "http://example.com/",
+                "children": [
+                    {
+                        "ID": "child/",
+                        "children": [{"ID": "grandchild"}],
+                    },
+                ],
+            },
+        )
+        registry = Registry().with_resource(root.id(), root)
+
+        resolver = registry.resolver()
+        first = resolver.lookup("http://example.com/")
+        assert first.contents == root.contents
+
+        with pytest.raises(exceptions.Unresolvable):
+            first.resolver.lookup("grandchild")
+
+        second = first.resolver.lookup("#/children/0")
+        third = second.resolver.lookup("grandchild")
+        assert third.contents == {"ID": "grandchild"}
+
 
 class TestSpecification:
     def test_create_resource(self):