Fix regression in filters.

The use of a `WeakValueDictionary` caused items to be removed from the cache.
This is not a global anymore, so a normal dict should be fine.

Author: jonathanslenders

src/prompt_toolkit/filters/base.py

@@ -1,6 +1,5 @@
 from __future__ import annotations
 
-import weakref
 from abc import ABCMeta, abstractmethod
 from typing import Callable, Dict, Iterable, List, Optional, Tuple, Union
 
@@ -16,12 +15,8 @@ class Filter(metaclass=ABCMeta):
     """
 
     def __init__(self) -> None:
-        self._and_cache: weakref.WeakValueDictionary[
-            Filter, _AndList
-        ] = weakref.WeakValueDictionary()
-        self._or_cache: weakref.WeakValueDictionary[
-            Filter, _OrList
-        ] = weakref.WeakValueDictionary()
+        self._and_cache: dict[Filter, _AndList] = {}
+        self._or_cache: dict[Filter, _OrList] = {}
         self._invert_result: Filter | None = None
 
     @abstractmethod

tests/test_filter.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import pytest
+import gc
 
 from prompt_toolkit.filters import Always, Condition, Filter, Never, to_filter
 
@@ -60,3 +61,25 @@ def test_to_filter():
 
     with pytest.raises(TypeError):
         to_filter(4)
+
+
+def test_filter_cache_regression_1():
+    # See: https://github.com/prompt-toolkit/python-prompt-toolkit/issues/1729
+
+    cond = Condition(lambda: True)
+
+    # The use of a `WeakValueDictionary` caused this following expression to
+    # fail. The problem is that the nested `(a & a)` expression gets garbage
+    # collected between the two statements and is removed from our cache.
+    x = (cond & cond) & cond
+    y = (cond & cond) & cond
+    assert x == y
+
+def test_filter_cache_regression_2():
+    cond1 = Condition(lambda: True)
+    cond2 = Condition(lambda: True)
+    cond3 = Condition(lambda: True)
+
+    x = (cond1 & cond2) & cond3
+    y = (cond1 & cond2) & cond3
+    assert x == y