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https://github.com/python/cpython/commit/c15ba304f35362470e29ea5626fed28366bc9571
commit: c15ba304f35362470e29ea5626fed28366bc9571
branch: 3.10
author: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
committer: ambv <lukasz@langa.pl>
date: 2021-10-20T00:07:13+02:00
summary:

bpo-39679: Add tests for classmethod/staticmethod singledispatchmethods (GH-29034) (GH-29072)

In Python 3.8 and 3.9, stacking `@functools.singledispatchmethod` on top of
`@classmethod` or `@staticmethod` caused an exception to be raised if the
method was registered using type-annotations rather than
`@method.register(int)`. This was not caught by unit tests, however, as the
tests only tested the `@method.register(int)` way of registering additional
implementations. The bug is no longer present in Python 3.10+, but
`test_functools.py` is still lacking regression tests for these cases. This
commit adds these test cases.
(cherry picked from commit ad6d162e518963711d24c80f1b7d6079bd437584)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

files:
A Misc/NEWS.d/next/Tests/2021-10-18-16-18-41.bpo-39679.F18qcE.rst
M Lib/test/test_functools.py

diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
index fece8256a3e26..bdb4ddcc60cac 100644
--- a/Lib/test/test_functools.py
+++ b/Lib/test/test_functools.py
@@ -2437,6 +2437,48 @@ def _(self, arg: str):
self.assertEqual(a.t(''), "str")
self.assertEqual(a.t(0.0), "base")

+ def test_staticmethod_type_ann_register(self):
+ class A:
+ @functools.singledispatchmethod
+ @staticmethod
+ def t(arg):
+ return arg
+ @t.register
+ @staticmethod
+ def _(arg: int):
+ return isinstance(arg, int)
+ @t.register
+ @staticmethod
+ def _(arg: str):
+ return isinstance(arg, str)
+ a = A()
+
+ self.assertTrue(A.t(0))
+ self.assertTrue(A.t(''))
+ self.assertEqual(A.t(0.0), 0.0)
+
+ def test_classmethod_type_ann_register(self):
+ class A:
+ def __init__(self, arg):
+ self.arg = arg
+
+ @functools.singledispatchmethod
+ @classmethod
+ def t(cls, arg):
+ return cls("base")
+ @t.register
+ @classmethod
+ def _(cls, arg: int):
+ return cls("int")
+ @t.register
+ @classmethod
+ def _(cls, arg: str):
+ return cls("str")
+
+ self.assertEqual(A.t(0).arg, "int")
+ self.assertEqual(A.t('').arg, "str")
+ self.assertEqual(A.t(0.0).arg, "base")
+
def test_invalid_registrations(self):
msg_prefix = "Invalid first argument to `register()`: "
msg_suffix = (
diff --git a/Misc/NEWS.d/next/Tests/2021-10-18-16-18-41.bpo-39679.F18qcE.rst b/Misc/NEWS.d/next/Tests/2021-10-18-16-18-41.bpo-39679.F18qcE.rst
new file mode 100644
index 0000000000000..b0d1b686392ef
--- /dev/null
+++ b/Misc/NEWS.d/next/Tests/2021-10-18-16-18-41.bpo-39679.F18qcE.rst
@@ -0,0 +1,2 @@
+Add more test cases for `@functools.singledispatchmethod` when combined with
+`@classmethod` or `@staticmethod`.

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