preserve extra sibling attributes

jsonref.py

@@ -1,6 +1,7 @@
 import functools
 import json
 import warnings
+import copy
 
 try:
     from collections.abc import Mapping, MutableMapping, Sequence
@@ -134,6 +135,10 @@ def __init__(
         self.store = _store  # Use the same object to be shared with children
         if self.store is None:
             self.store = _URIDict()
+        self.extra = None
+        if isinstance(refobj, Mapping) and len(refobj.keys()) > 1:
+            self.extra = copy.deepcopy(refobj)
+            del self.extra["$ref"]
 
     @property
     def _ref_kwargs(self):
@@ -192,7 +197,10 @@ def resolve_pointer(self, document, pointer):
                 except ValueError:
                     pass
             try:
-                document = document[part]
+                if self.extra:
+                    document = {**document[part], **self.extra}
+                else:
+                    document = document[part]
             except (TypeError, LookupError) as e:
                 self._error("Unresolvable JSON pointer: %r" % pointer, cause=e)
         return document

tests.py

@@ -67,14 +67,38 @@ def test_actual_references_not_copies(self):
     def test_ignored_sibling_attributes(self):
         json = {
             "a": {"type": "object", "properties": {"foo": {"type": "string"}}},
-           "b": {"extra": "foobar", "$ref": "#/a"},
+            "b": {"extra": "foobar", "$ref": "#/a"},
+            "c": {"extra": { "more": "bar", "$ref": "#/a"} },
         }
         result = JsonRef.replace_refs(json)
-        assert result["b"].__subject__ is {
+        # because we deepcopy, use '==' instead of 'is"
+        assert result["b"] == {
             "extra": "foobar",
             "type": "object",
             "properties": {"foo": {"type": "string"}},
         }
+        assert result["c"] == {
+            "extra": {
+                "more": "bar",
+                "type": "object",
+                "properties": {"foo": {"type": "string"}}
+            }
+        }
+
+    def test_extra_sibling_attributes_list_ref(self):
+        json = {
+            "a": ["target"],
+            "b": {"extra": "foobar", "$ref": "#/a"},
+        }
+        result = JsonRef.replace_refs(json)
+        with pytest.raises(JsonRefError) as excinfo:
+            result["b"].__subject__
+        e = excinfo.value
+        assert e.reference == json["b"]
+        assert e.uri == "#/a"
+        assert e.base_uri == ""
+        assert e.path == ["b"]
+        assert type(e.cause) == TypeError
 
     def test_recursive_data_structures_local(self):
         json = {"a": "foobar", "b": {"$ref": "#"}}