deprecated weakkeycache by specifying in __init__

scrapy/utils/python.py

@@ -7,10 +7,12 @@ import inspect
 import re
 import sys
 import weakref
+import warnings
 from functools import partial, wraps
 from itertools import chain
 
 from scrapy.utils.decorators import deprecated
+from scrapy.exceptions import ScrapyDeprecationWarning
 
 
 def flatten(x):
@@ -275,10 +277,10 @@ def equal_attributes(obj1, obj2, attributes):
     return True
 
 
-@deprecated
 class WeakKeyCache:
 
     def __init__(self, default_factory):
+        warnings.warn("Call to deprecated Class WeakKeyCache", category=ScrapyDeprecationWarning, stacklevel=2)
         self.default_factory = default_factory
         self._weakdict = weakref.WeakKeyDictionary()
 

scrapy/utils/tester.py

@@ -0,0 +1,3 @@
+from scrapy.utils.decorators import deprecated
+
+

tests/test_utils_python.py

@@ -1,15 +1,18 @@
 import functools
+import gc
 import operator
 import platform
 import unittest
+from itertools import count
 from sys import version_info
 from warnings import catch_warnings
 
 from scrapy.utils.python import (
     memoizemethod_noargs, binary_is_text, equal_attributes,
-    get_func_args, to_bytes, to_unicode,
+    WeakKeyCache, get_func_args, to_bytes, to_unicode,
     without_none_values, MutableChain)
 
+
 __doctests__ = ['scrapy.utils.python']
 
 
@@ -152,6 +155,23 @@ class UtilsPythonTestCase(unittest.TestCase):
         a.meta['z'] = 2
         self.assertFalse(equal_attributes(a, b, [compare_z, 'x']))
 
+    def test_weakkeycache(self):
+        class _Weakme:
+            pass
+
+        _values = count()
+        wk = WeakKeyCache(lambda k: next(_values))
+        k = _Weakme()
+        v = wk[k]
+        self.assertEqual(v, wk[k])
+        self.assertNotEqual(v, wk[_Weakme()])
+        self.assertEqual(v, wk[k])
+        del k
+        for _ in range(100):
+            if wk._weakdict:
+                gc.collect()
+        self.assertFalse(len(wk._weakdict))
+
     def test_get_func_args(self):
         def f1(a, b, c):
             pass