Fix a regression with RefResolver-based resolution in newly created drafts

We need a bit more state management to serve `RefResolver` until it's
fully removed :/

(The handler here is simply to avoid needing to hit some remote
reference.)

Refs: #1061 (comment)

Author: Julian

Diff for: CHANGELOG.rst

@@ -1,3 +1,8 @@
+v4.18.1
+=======
+
+* Fix a regression with ``jsonschema.RefResolver`` based resolution when used in combination with a custom validation dialect (via ``jsonschema.validators.create``).
+
 v4.18.0
 =======
 

Diff for: jsonschema/tests/test_validators.py

@@ -2373,6 +2373,28 @@ def test_pointer_within_schema_with_different_id(self):
         validator = validators.Draft7Validator(another, resolver=two)
         self.assertFalse(validator.is_valid({"maxLength": "foo"}))
 
+    def test_newly_created_validator_with_ref_resolver(self):
+        """
+        See https://github.com/python-jsonschema/jsonschema/issues/1061#issuecomment-1624266555.
+        """  # noqa: E501
+
+        def handle(uri):
+            self.assertEqual(uri, "http://example.com/foo")
+            return {"type": "integer"}
+
+        resolver = validators._RefResolver("", {}, handlers={"http": handle})
+        Validator = validators.create(
+            meta_schema={},
+            validators=validators.Draft4Validator.VALIDATORS,
+        )
+        schema = {"$id": "http://example.com/bar", "$ref": "foo"}
+        validator = Validator(schema, resolver=resolver)
+        self.assertEqual(
+            (validator.is_valid({}), validator.is_valid(37)),
+            (False, True),
+        )
+
+
 
 def sorted_errors(errors):
     def key(error):

Diff for: jsonschema/validators.py

@@ -275,6 +275,11 @@ def __attrs_post_init__(self):
                 resource = specification.create_resource(self.schema)
                 self._resolver = registry.resolver_with_root(resource)
 
+            # REMOVEME: Legacy ref resolution state management.
+            push_scope = getattr(self._ref_resolver, "push_scope", None)
+            if push_scope is not None:
+                push_scope(id_of(self.schema))
+
         @classmethod
         def check_schema(cls, schema, format_checker=_UNSET):
             Validator = validator_for(cls.META_SCHEMA, default=cls)