1 files changed, 45 insertions, 0 deletions
diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
index 824549b803..63fe83e5db 100644
--- a/Lib/test/test_functools.py
+++ b/Lib/test/test_functools.py
@@ -9,6 +9,7 @@ import sys
 from test import support
 import time
 import unittest
+import unittest.mock
 from weakref import proxy
 import contextlib
 try:
@@ -1191,6 +1192,41 @@ class TestLRU:
         self.assertEqual(misses, 4)
         self.assertEqual(currsize, 2)
 
+    def test_lru_hash_only_once(self):
+        # To protect against weird reentrancy bugs and to improve
+        # efficiency when faced with slow __hash__ methods, the
+        # LRU cache guarantees that it will only call __hash__
+        # only once per use as an argument to the cached function.
+
+        @self.module.lru_cache(maxsize=1)
+        def f(x, y):
+            return x * 3 + y
+
+        # Simulate the integer 5
+        mock_int = unittest.mock.Mock()
+        mock_int.__mul__ = unittest.mock.Mock(return_value=15)
+        mock_int.__hash__ = unittest.mock.Mock(return_value=999)
+
+        # Add to cache:  One use as an argument gives one call
+        self.assertEqual(f(mock_int, 1), 16)
+        self.assertEqual(mock_int.__hash__.call_count, 1)
+        self.assertEqual(f.cache_info(), (0, 1, 1, 1))
+
+        # Cache hit: One use as an argument gives one additional call
+        self.assertEqual(f(mock_int, 1), 16)
+        self.assertEqual(mock_int.__hash__.call_count, 2)
+        self.assertEqual(f.cache_info(), (1, 1, 1, 1))
+
+        # Cache eviction: No use as an argument gives no additonal call
+        self.assertEqual(f(6, 2), 20)
+        self.assertEqual(mock_int.__hash__.call_count, 2)
+        self.assertEqual(f.cache_info(), (1, 2, 1, 1))
+
+        # Cache miss: One use as an argument gives one additional call
+        self.assertEqual(f(mock_int, 1), 16)
+        self.assertEqual(mock_int.__hash__.call_count, 3)
+        self.assertEqual(f.cache_info(), (1, 3, 1, 1))
+
     def test_lru_reentrancy_with_len(self):
         # Test to make sure the LRU cache code isn't thrown-off by
         # caching the built-in len() function.  Since len() can be
@@ -1203,6 +1239,15 @@ class TestLRU:
         finally:
             builtins.len = old_len
 
+    def test_lru_star_arg_handling(self):
+        # Test regression that arose in ea064ff3c10f
+        @functools.lru_cache()
+        def f(*args):
+            return args
+
+        self.assertEqual(f(1, 2), (1, 2))
+        self.assertEqual(f((1, 2)), ((1, 2),))
+
     def test_lru_type_error(self):
         # Regression test for issue #28653.
         # lru_cache was leaking when one of the arguments