Issue 22184: Early detection and reporting of missing lru_cache parameters
diff --git a/Lib/functools.py b/Lib/functools.py
index b8463ad..24fdb16 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -392,6 +392,12 @@
# The internals of the lru_cache are encapsulated for thread safety and
# to allow the implementation to change (including a possible C version).
+ # Early detection of an erroneous call to @lru_cache without any arguments
+ # resulting in the inner function being passed to maxsize instead of an
+ # integer or None.
+ if maxsize is not None and not isinstance(maxsize, int):
+ raise TypeError('Expected maxsize to be an integer or None')
+
# Constants shared by all lru cache instances:
sentinel = object() # unique object used to signal cache misses
make_key = _make_key # build a key from the function arguments
diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
index 75ae7f3..a7e5c7e 100644
--- a/Lib/test/test_functools.py
+++ b/Lib/test/test_functools.py
@@ -1070,6 +1070,13 @@
self.assertEqual(test_func(DoubleEq(2)), # Trigger a re-entrant __eq__ call
DoubleEq(2)) # Verify the correct return value
+ def test_early_detection_of_bad_call(self):
+ # Issue #22184
+ with self.assertRaises(TypeError):
+ @functools.lru_cache
+ def f():
+ pass
+
class TestSingleDispatch(unittest.TestCase):
def test_simple_overloads(self):