Fix #256: Deprecate MRUCache class.

docs/index.rst

@@ -96,6 +96,12 @@ computed when the item is inserted into the cache.
    This class discards the most recently used items first to make
    space when necessary.
 
+   .. deprecated:: 5.4
+
+   `MRUCache` has been deprecated due to lack of use, to reduce
+   maintenance.  Please choose another cache implementation that suits
+   your needs.
+
 .. autoclass:: RRCache(maxsize, choice=random.choice, getsizeof=None)
    :members: choice, popitem
 

src/cachetools/__init__.py

@@ -241,6 +241,10 @@ class MRUCache(Cache):
     """Most Recently Used (MRU) cache implementation."""
 
     def __init__(self, maxsize, getsizeof=None):
+        from warnings import warn
+
+        warn("MRUCache is deprecated", DeprecationWarning, stacklevel=2)
+
         Cache.__init__(self, maxsize, getsizeof)
         self.__order = collections.OrderedDict()
 

tests/test_func.py

@@ -118,7 +118,7 @@ def decorator(self, maxsize, **kwargs):
         with warnings.catch_warnings(record=True) as w:
             warnings.simplefilter("always")
             d = cachetools.func.mru_cache(maxsize, **kwargs)
-        self.assertEqual(len(w), 1)
+        self.assertNotEqual(len(w), 0)
         self.assertIs(w[0].category, DeprecationWarning)
         return d
 

tests/test_mru.py

@@ -1,4 +1,5 @@
 import unittest
+import warnings
 
 from cachetools import MRUCache
 
@@ -7,10 +8,16 @@
 
 class MRUCacheTest(unittest.TestCase, CacheTestMixin):
 
+    # TODO: method to create cache that can be overridden
     Cache = MRUCache
 
     def test_evict__writes_only(self):
-        cache = MRUCache(maxsize=2)
+
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always")
+            cache = MRUCache(maxsize=2)
+        self.assertEqual(len(w), 1)
+        self.assertIs(w[0].category, DeprecationWarning)
 
         cache[1] = 1
         cache[2] = 2
@@ -22,7 +29,11 @@ def test_evict__writes_only(self):
         assert 3 in cache
 
     def test_evict__with_access(self):
-        cache = MRUCache(maxsize=2)
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always")
+            cache = MRUCache(maxsize=2)
+        self.assertEqual(len(w), 1)
+        self.assertIs(w[0].category, DeprecationWarning)
 
         cache[1] = 1
         cache[2] = 2
@@ -34,7 +45,11 @@ def test_evict__with_access(self):
         assert 3 in cache
 
     def test_evict__with_delete(self):
-        cache = MRUCache(maxsize=2)
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always")
+            cache = MRUCache(maxsize=2)
+        self.assertEqual(len(w), 1)
+        self.assertIs(w[0].category, DeprecationWarning)
 
         cache[1] = 1
         cache[2] = 2