Catch non-existent pointers too.

Author: Julian

referencing/_core.py

@@ -239,9 +239,9 @@ def lookup(self, ref: URI) -> Resolved[D]:
         uri, fragment = urldefrag(urljoin(self._base_uri, ref))
         try:
             resource = self._registry[uri]
+            if fragment.startswith("/"):
+                return resource.pointer(pointer=fragment, resolver=self)
         except KeyError:
             raise Unresolvable(ref=ref) from None
-        if fragment.startswith("/"):
-            return resource.pointer(pointer=fragment, resolver=self)
 
         return Resolved(contents=resource.contents, resolver=self)

referencing/tests/test_core.py

@@ -224,6 +224,14 @@ def test_lookup_unknown_reference(self):
             resolver.lookup(ref)
         assert e.value == exceptions.Unresolvable(ref=ref)
 
+    def test_lookup_non_existent_pointer(self):
+        resource = Resource.opaque({"foo": {}})
+        resolver = Registry({"http://example.com/1": resource}).resolver()
+        ref = "http://example.com/1#/foo/bar"
+        with pytest.raises(exceptions.Unresolvable) as e:
+            resolver.lookup(ref)
+        assert e.value == exceptions.Unresolvable(ref=ref)
+
 
 class TestSpecification:
     def test_create_resource(self):