Only calculate hash once for Marker objects (alecthomas#513)

voluptuous/schema_builder.py

@@ -9,7 +9,7 @@
 import typing
 from collections.abc import Generator
 from contextlib import contextmanager
-from functools import wraps
+from functools import cache, wraps
 
 from voluptuous import error as er
 from voluptuous.error import Error
@@ -1026,6 +1026,8 @@ class Marker(object):
     introspected by any external tool, for example to generate schema documentation.
     """
 
+    __slots__ = ('schema', '_schema', 'msg', 'description', '__hash__')
+
     def __init__(
         self,
         schema_: Schemable,
@@ -1036,6 +1038,7 @@ def __init__(
         self._schema = Schema(schema_)
         self.msg = msg
         self.description = description
+        self.__hash__ = cache(lambda: hash(schema_))  # type: ignore[method-assign]
 
     def __call__(self, v):
         try:
@@ -1056,9 +1059,6 @@ def __lt__(self, other):
             return self.schema < other.schema
         return self.schema < other
 
-    def __hash__(self):
-        return hash(self.schema)
-
     def __eq__(self, other):
         return self.schema == other
 
@@ -1244,16 +1244,22 @@ class Remove(Marker):
     [1, 2, 3, 5, '7']
     """
 
+    def __init__(
+        self,
+        schema_: Schemable,
+        msg: typing.Optional[str] = None,
+        description: typing.Optional[str] = None,
+    ) -> None:
+        super().__init__(schema_, msg, description)
+        self.__hash__ = cache(lambda: object.__hash__(self))  # type: ignore[method-assign]
+
     def __call__(self, schema: Schemable):
         super(Remove, self).__call__(schema)
         return self.__class__
 
     def __repr__(self):
         return "Remove(%r)" % (self.schema,)
 
-    def __hash__(self):
-        return object.__hash__(self)
-
 
 def message(
     default: typing.Optional[str] = None,

voluptuous/tests/tests.py

@@ -1072,6 +1072,7 @@ def test_marker_hashable():
     assert definition.get('y') == float
     assert Required('x') == Required('x')
     assert Required('x') != Required('y')
+    assert hash(Required('x').schema) == hash(Required('x'))
     # Remove markers are not hashable
     assert definition.get('j') is None