bpo-45701: add tuple tests with lru_cache to test_functools

Author: sobolevn

Lib/test/test_functools.py

@@ -1495,6 +1495,59 @@ def square(x):
             self.assertEqual(square.cache_info().hits, 4)
             self.assertEqual(square.cache_info().misses, 4)
 
+    def test_lru_with_container_types(self):
+        def identity(x):
+            return x
+
+        values = [(), (1, 2), (1, 2, 'a')]
+        for maxsize in (None, 128):
+            for current_value in values:
+                with self.subTest(current_value=current_value, maxsize=maxsize):
+                    cached = self.module.lru_cache(maxsize, typed=True)(identity)
+
+                    # some unrelated tuple:
+                    cached((1, 2, 3, 4, 5))  # miss
+                    cached((1, 2, 3, 4, 5))  # hit
+
+                    cached(current_value)  # miss
+                    res = cached(current_value)  # hit
+
+                    self.assertEqual(res, current_value)
+                    self.assertEqual(cached.cache_info().hits, 2)
+                    self.assertEqual(cached.cache_info().misses, 2)
+
+    def test_lru_with_container_types_hash_collision(self):
+        # https://bugs.python.org/issue45701
+        def get_zeroth(x):
+            return x[0]
+
+        values = [
+            # All values inside each tuple have the same hash:
+            # `hash(1) == hash(1.0) == hash(True)`
+            (0, 0.0, False),
+            (1, 1.0, True),
+        ]
+        for maxsize in (None, 128):
+            for hash_collision in values:
+                with self.subTest(maxsize=maxsize, values=values):
+                    cached = self.module.lru_cache(
+                        maxsize,
+                        typed=True,
+                    )(get_zeroth)
+
+                    # All these calls will be cached, because hash is the same.
+                    self.assertEqual(type(hash_collision[0]), int)
+                    self.assertEqual(  # miss, cache created
+                        type(cached((hash_collision[0], 2))),
+                        int,
+                    )
+
+                    for value in hash_collision:  # 3 hits
+                        self.assertEqual(type(cached((value, 2))), int)
+
+                    self.assertEqual(cached.cache_info().hits, 3)
+                    self.assertEqual(cached.cache_info().misses, 1)
+
     def test_lru_with_keyword_args(self):
         @self.module.lru_cache()
         def fib(n):

Misc/NEWS.d/next/Tests/2021-10-31-10-58-45.bpo-45701.r0LAUL.rst

@@ -0,0 +1,2 @@
+Add tests with ``tuple`` type with :func:`functools.lru_cache` to
+``test_functools``.