fixtures: use exception group when multiple finalizers raise in fixture teardown

Previously, if more than one fixture finalizer raised, only the first
was reported, and the other errors were lost.

Use an exception group to report them all. This is similar to the change
we made in node teardowns (in `SetupState`).

Author: bluetech

changelog/12047.improvement.rst

@@ -0,0 +1,2 @@
+When multiple finalizers of a fixture raise an exception, now all exceptions are reported as an exception group.
+Previously, only the first exception was reported.

src/_pytest/fixtures.py

@@ -7,6 +7,7 @@
 import inspect
 import os
 from pathlib import Path
+import sys
 from typing import AbstractSet
 from typing import Any
 from typing import Callable
@@ -67,6 +68,10 @@
 from _pytest.scope import Scope
 
 
+if sys.version_info[:2] < (3, 11):
+    from exceptiongroup import BaseExceptionGroup
+
+
 if TYPE_CHECKING:
     from typing import Deque
 
@@ -1017,27 +1022,25 @@ def addfinalizer(self, finalizer: Callable[[], object]) -> None:
         self._finalizers.append(finalizer)
 
     def finish(self, request: SubRequest) -> None:
-        exc = None
-        try:
-            while self._finalizers:
-                try:
-                    func = self._finalizers.pop()
-                    func()
-                except BaseException as e:
-                    # XXX Only first exception will be seen by user,
-                    #     ideally all should be reported.
-                    if exc is None:
-                        exc = e
-            if exc:
-                raise exc
-        finally:
-            ihook = request.node.ihook
-            ihook.pytest_fixture_post_finalizer(fixturedef=self, request=request)
-            # Even if finalization fails, we invalidate the cached fixture
-            # value and remove all finalizers because they may be bound methods
-            # which will keep instances alive.
-            self.cached_result = None
-            self._finalizers.clear()
+        exceptions: List[BaseException] = []
+        while self._finalizers:
+            fin = self._finalizers.pop()
+            try:
+                fin()
+            except BaseException as e:
+                exceptions.append(e)
+        node = request.node
+        node.ihook.pytest_fixture_post_finalizer(fixturedef=self, request=request)
+        # Even if finalization fails, we invalidate the cached fixture
+        # value and remove all finalizers because they may be bound methods
+        # which will keep instances alive.
+        self.cached_result = None
+        self._finalizers.clear()
+        if len(exceptions) == 1:
+            raise exceptions[0]
+        elif len(exceptions) > 1:
+            msg = f'errors while tearing down fixture "{self.argname}" of {node}'
+            raise BaseExceptionGroup(msg, exceptions[::-1])
 
     def execute(self, request: SubRequest) -> FixtureValue:
         # Get required arguments and register our own finish()

testing/python/fixtures.py

@@ -932,8 +932,9 @@ def test_request_subrequest_addfinalizer_exceptions(
         self, pytester: Pytester
     ) -> None:
         """
-        Ensure exceptions raised during teardown by a finalizer are suppressed
-        until all finalizers are called, re-raising the first exception (#2440)
+        Ensure exceptions raised during teardown by finalizers are suppressed
+        until all finalizers are called, then re-reaised together in an
+        exception group (#2440)
         """
         pytester.makepyfile(
             """
@@ -960,8 +961,16 @@ def test_second():
         """
         )
         result = pytester.runpytest()
+        result.assert_outcomes(passed=2, errors=1)
         result.stdout.fnmatch_lines(
-            ["*Exception: Error in excepts fixture", "* 2 passed, 1 error in *"]
+            [
+                '  | *ExceptionGroup: errors while tearing down fixture "subrequest" of <Function test_first> (2 sub-exceptions)',  # noqa: E501
+                "  +-+---------------- 1 ----------------",
+                "    | Exception: Error in something fixture",
+                "    +---------------- 2 ----------------",
+                "    | Exception: Error in excepts fixture",
+                "    +------------------------------------",
+            ],
         )
 
     def test_request_getmodulepath(self, pytester: Pytester) -> None: