Merge pull request #14620 from pytest-dev/patchback/backports/9.1.x/680f9f3ed3faaaa9a4fd1d8120618cd17cdee2d0/pr-14220

[PR #14220/680f9f3e backport][9.1.x] raises: fix stale loop variable in RaisesGroup error reporting

Author: bluetech

changelog/14220.bugfix.rst

@@ -0,0 +1 @@
+Fixed a logic bug in :class:`pytest.RaisesGroup` which would might cause it to display incorrect "It matches `FooError()` which was paired with `BarError`" messages.

src/_pytest/raises.py

@@ -1354,7 +1354,7 @@ def _check_exceptions(
                 f"\n{indent_1}{self._repr_expected(self.expected_exceptions[i_failed])}"
             )
             for i_actual, actual in enumerate(actual_exceptions):
-                if results.get_result(i_exp, i_actual) is None:
+                if results.get_result(i_failed, i_actual) is None:
                     # we print full repr of match target
                     s += (
                         f"\n{indent_2}It matches {backquote(repr(actual))} which was paired with "

testing/python/raises_group.py

@@ -1350,3 +1350,21 @@ def test_tuples() -> None:
         ),
     ):
         RaisesGroup((ValueError, IndexError))  # type: ignore[call-overload]
+
+
+def test_expected_matching_only_on_matching() -> None:
+    """Regression test for #14220, logic error which caused the "which was
+    paired with" message to appear for wrong pairs."""
+    with (
+        fails_raises_group(
+            "\n"
+            "1 matched exception. \n"
+            "Too few exceptions raised!\n"
+            "The following expected exceptions did not find a match:\n"
+            "  ValueError\n"
+            "  TypeError\n"
+            "    It matches `TypeError()` which was paired with `TypeError`",
+        ),
+        RaisesGroup(TypeError, ValueError, TypeError),
+    ):
+        raise ExceptionGroup("", [TypeError()])