Bug report

Bug description:

Also reported upstream to Djangohere.

The following code works on Python 3.12 and I believe#85160 is the cause.

When traversing a relationship and then calling asingledispatchmethod method registered on a model, the reference to self seems to get cached and locked to the first created model.

classTest(models.Model):    ...classTest2(models.Model):relationship=models.ForeignKey("Test",on_delete=models.CASCADE)@singledispatchmethoddefbug(self,x):print(">",id(self))@bug.registerdef_(self,x:int):print(">",id(self))

and then it's pretty easy to trigger:

fortintest.test2_set.all():print("id:",id(t))# always changest.bug(4)# only ever prints a single id

CPython versions tested on:

3.13

Operating systems tested on:

macOS

Linked PRs

• gh-127750: Improve caching in singledispatchmethod #127751
• gh-127750: Fix singledispatchmethod caching #127839
• gh-127750: Fix singledispatchmethod caching (v2) #128648
• gh-127750: Fix and optimize functools.singledispatchmethod() #130008
• [3.13] gh-127750: Fix functools.singledispatchmethod() #130029
• gh-127750: Improve repr of functools.singledispatchmethod #130220
• gh-127750: Restore inspect and pydoc support of singledispatchmethod #130309
• [3.13] gh-127750: Backport some tests for singledispatchmethod (GH-130309) #130340
• [3.12] gh-127750: Backport some tests for singledispatchmethod (GH-130309) (GH-130340) #130341