PR feedback: Raise warnings in the new properties for shouldstop and shouldfail, add unit test to test_session.py

src/_pytest/main.py

@@ -6,6 +6,7 @@ import functools
 import importlib
 import os
 import sys
+import warnings
 from pathlib import Path
 from typing import AbstractSet
 from typing import Callable
@@ -44,6 +45,7 @@ from _pytest.reports import CollectReport
 from _pytest.reports import TestReport
 from _pytest.runner import collect_one_node
 from _pytest.runner import SetupState
+from _pytest.warning_types import PytestWarning
 
 
 def pytest_addoption(parser: Parser) -> None:
@@ -584,6 +586,12 @@ class Session(nodes.Collector):
     def shouldstop(self, value: Union[bool, str]) -> None:
         """Prevent plugins from setting this to False once it has been set."""
         if value is False and self._shouldstop:
+            warnings.warn(
+                PytestWarning(
+                    "session.shouldstop cannot be unset after it has been set; ignoring."
+                ),
+                stacklevel=2,
+            )
             return
         self._shouldstop = value
 
@@ -595,6 +603,12 @@ class Session(nodes.Collector):
     def shouldfail(self, value: Union[bool, str]) -> None:
         """Prevent plugins from setting this to False once it has been set."""
         if value is False and self._shouldfail:
+            warnings.warn(
+                PytestWarning(
+                    "session.shouldfail cannot be unset after it has been set; ignoring."
+                ),
+                stacklevel=2,
+            )
             return
         self._shouldfail = value
 

src/_pytest/runner.py

@@ -131,12 +131,10 @@ def runtestprotocol(
             show_test_item(item)
         if not item.config.getoption("setuponly", False):
             reports.append(call_and_report(item, "call", log))
-
     # If the session is about to fail or stop, teardown everything - this is
     # necessary to correctly report fixture teardown errors (see #11706)
     if item.session.shouldfail or item.session.shouldstop:
         nextitem = None
-
     reports.append(call_and_report(item, "teardown", log, nextitem=nextitem))
     # After all teardown hooks have been called
     # want funcargs and request info to go away.

testing/test_session.py

@@ -418,3 +418,27 @@ def test_rootdir_wrong_option_arg(pytester: Pytester) -> None:
     result.stderr.fnmatch_lines(
         ["*Directory *wrong_dir* not found. Check your '--rootdir' option.*"]
     )
+
+
+def test_shouldfail_is_sticky(pytester: Pytester) -> None:
+    """Test that session.shouldfail cannot be reset to False after being set."""
+    pytester.makeconftest(
+        """
+        def pytest_sessionfinish(session, exitstatus):
+            session.shouldfail = False
+    """
+    )
+
+    pytester.makepyfile(
+        """
+        import pytest
+
+        def test_foo():
+            pytest.fail("This is a failing test")
+
+        def test_bar():
+            pass
+    """
+    )
+    result = pytester.runpytest("--maxfail=1")
+    result.stderr.fnmatch_lines("*session.shouldfail cannot be unset*")