python3Packages.exceptiongroup: fix build on staging (#487915)

pkgs/development/python-modules/exceptiongroup/default.nix

@@ -6,6 +6,7 @@
   pytestCheckHook,
   pythonAtLeast,
   pythonOlder,
+  isPy313,
   typing-extensions,
 }:
 
@@ -21,6 +22,15 @@ buildPythonPackage rec {
     hash = "sha256-3WInufN+Pp6vB/Gik6e8V1a34Dr/oiH3wDMB+2lHRMM=";
   };
 
+  # CPython fixed https://github.com/python/cpython/issues/141732 in
+  # https://github.com/python/cpython/pull/141736, but exceptiongroup 1.3.1,
+  # including its test suite, still matches the old repr behavior.
+  # The CPython fix has only been backported to 3.13 so far, where it was
+  # first included in version 3.13.12, so we only need to patch for 3.13
+  # and 3.15+.
+  # Upstream issue: https://github.com/agronholm/exceptiongroup/issues/154
+  patches = lib.optional (isPy313 || pythonAtLeast "3.15") ./match-repr-fix.patch;
+
   build-system = [ flit-scm ];
 
   dependencies = lib.optionals (pythonOlder "3.13") [ typing-extensions ];

pkgs/development/python-modules/exceptiongroup/match-repr-fix.patch

@@ -0,0 +1,48 @@
+From 9be2b65dbd8366da27cd79c09195493217dbf539 Mon Sep 17 00:00:00 2001
+From: Tom Hunze <dev@thunze.de>
+Date: Sat, 7 Feb 2026 11:37:49 +0100
+Subject: [PATCH] Fix `ExceptionGroup` repr changing when original exception
+ sequence is mutated
+
+https://github.com/python/cpython/pull/141736
+---
+ src/exceptiongroup/_exceptions.py | 3 ++-
+ tests/test_exceptions.py          | 3 +--
+ 2 files changed, 3 insertions(+), 3 deletions(-)
+
+diff --git a/src/exceptiongroup/_exceptions.py b/src/exceptiongroup/_exceptions.py
+index f42c1ad..996d8e1 100644
+--- a/src/exceptiongroup/_exceptions.py
++++ b/src/exceptiongroup/_exceptions.py
+@@ -101,6 +101,7 @@ class BaseExceptionGroup(BaseException, Generic[_BaseExceptionT_co]):
+                         )
+ 
+         instance = super().__new__(cls, __message, __exceptions)
++        instance._exceptions_str = repr(__exceptions)
+         instance._exceptions = tuple(__exceptions)
+         return instance
+ 
+@@ -275,7 +276,7 @@ class BaseExceptionGroup(BaseException, Generic[_BaseExceptionT_co]):
+         return f"{self.message} ({len(self._exceptions)} sub-exception{suffix})"
+ 
+     def __repr__(self) -> str:
+-        return f"{self.__class__.__name__}({self.args[0]!r}, {self.args[1]!r})"
++        return f"{self.__class__.__name__}({self.args[0]!r}, {self._exceptions_str})"
+ 
+ 
+ class ExceptionGroup(BaseExceptionGroup[_ExceptionT_co], Exception):
+diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
+index e2bc81a..a253236 100644
+--- a/tests/test_exceptions.py
++++ b/tests/test_exceptions.py
+@@ -883,6 +883,5 @@ def test_exceptions_mutate_original_sequence():
+     exceptions.append(KeyError("bar"))
+     assert excgrp.exceptions is exc_tuple
+     assert repr(excgrp) == (
+-        "BaseExceptionGroup('foo', [ValueError(1), KeyboardInterrupt(), "
+-        "KeyError('bar')])"
++        "BaseExceptionGroup('foo', [ValueError(1), KeyboardInterrupt()])"
+     )
+-- 
+2.51.2
+