[PR #13525/391324e1 backport][8.4.x] pytester: avoid unraisableexception gc collects in inline runs to speed up test suite

src/_pytest/pytester.py

@@ -1092,6 +1092,8 @@ def inline_run(
             Typically we reraise keyboard interrupts from the child run. If
             True, the KeyboardInterrupt exception is captured.
         """
+        from _pytest.unraisableexception import gc_collect_iterations_key
+
         # (maybe a cpython bug?) the importlib cache sometimes isn't updated
         # properly between file creation and inline_run (especially if imports
         # are interspersed with file creation)
@@ -1115,12 +1117,16 @@ def inline_run(
 
             rec = []
 
-            class Collect:
+            class PytesterHelperPlugin:
                 @staticmethod
                 def pytest_configure(config: Config) -> None:
                     rec.append(self.make_hook_recorder(config.pluginmanager))
 
-            plugins.append(Collect())
+                    # The unraisable plugin GC collect slows down inline
+                    # pytester runs too much.
+                    config.stash[gc_collect_iterations_key] = 0
+
+            plugins.append(PytesterHelperPlugin())
             ret = main([str(x) for x in args], plugins=plugins)
             if len(rec) == 1:
                 reprec = rec.pop()

src/_pytest/unraisableexception.py

@@ -24,10 +24,12 @@
     from exceptiongroup import ExceptionGroup
 
 
-def gc_collect_harder() -> None:
-    # A single collection doesn't necessarily collect everything.
-    # Constant determined experimentally by the Trio project.
-    for _ in range(5):
+# This is a stash item and not a simple constant to allow pytester to override it.
+gc_collect_iterations_key = StashKey[int]()
+
+
+def gc_collect_harder(iterations: int) -> None:
+    for _ in range(iterations):
         gc.collect()
 
 
@@ -84,9 +86,12 @@ def collect_unraisable(config: Config) -> None:
 def cleanup(
     *, config: Config, prev_hook: Callable[[sys.UnraisableHookArgs], object]
 ) -> None:
+    # A single collection doesn't necessarily collect everything.
+    # Constant determined experimentally by the Trio project.
+    gc_collect_iterations = config.stash.get(gc_collect_iterations_key, 5)
     try:
         try:
-            gc_collect_harder()
+            gc_collect_harder(gc_collect_iterations)
             collect_unraisable(config)
         finally:
             sys.unraisablehook = prev_hook

testing/test_config.py

@@ -2175,7 +2175,8 @@ class DummyPlugin:
     plugins = config.invocation_params.plugins
     assert len(plugins) == 2
     assert plugins[0] is plugin
-    assert type(plugins[1]).__name__ == "Collect"  # installed by pytester.inline_run()
+    # Installed by pytester.inline_run().
+    assert type(plugins[1]).__name__ == "PytesterHelperPlugin"
 
     # args cannot be None
     with pytest.raises(TypeError):

testing/test_unraisableexception.py

@@ -1,7 +1,5 @@
 from __future__ import annotations
 
-from collections.abc import Generator
-import contextlib
 import gc
 import sys
 from unittest import mock
@@ -229,19 +227,13 @@ def _set_gc_state(enabled: bool) -> bool:
     return was_enabled
 
 
-@contextlib.contextmanager
-def _disable_gc() -> Generator[None]:
-    was_enabled = _set_gc_state(enabled=False)
-    try:
-        yield
-    finally:
-        _set_gc_state(enabled=was_enabled)
-
-
 def test_refcycle_unraisable(pytester: Pytester) -> None:
     # see: https://github.com/pytest-dev/pytest/issues/10404
     pytester.makepyfile(
         test_it="""
+        # Should catch the unraisable exception even if gc is disabled.
+        import gc; gc.disable()
+
         import pytest
 
         class BrokenDel:
@@ -256,23 +248,22 @@ def test_it():
         """
     )
 
-    with _disable_gc():
-        result = pytester.runpytest()
+    result = pytester.runpytest_subprocess(
+        "-Wdefault::pytest.PytestUnraisableExceptionWarning"
+    )
 
-    # TODO: should be a test failure or error
-    assert result.ret == pytest.ExitCode.INTERNAL_ERROR
+    assert result.ret == 0
 
     result.assert_outcomes(passed=1)
     result.stderr.fnmatch_lines("ValueError: del is broken")
 
 
-@pytest.mark.filterwarnings("default::pytest.PytestUnraisableExceptionWarning")
 def test_refcycle_unraisable_warning_filter(pytester: Pytester) -> None:
-    # note that the host pytest warning filter is disabled and the pytester
-    # warning filter applies during config teardown of unraisablehook.
-    # see: https://github.com/pytest-dev/pytest/issues/10404
     pytester.makepyfile(
         test_it="""
+        # Should catch the unraisable exception even if gc is disabled.
+        import gc; gc.disable()
+
         import pytest
 
         class BrokenDel:
@@ -287,17 +278,18 @@ def test_it():
         """
     )
 
-    with _disable_gc():
-        result = pytester.runpytest("-Werror")
+    result = pytester.runpytest_subprocess(
+        "-Werror::pytest.PytestUnraisableExceptionWarning"
+    )
 
-    # TODO: should be a test failure or error
-    assert result.ret == pytest.ExitCode.INTERNAL_ERROR
+    # TODO: Should be a test failure or error. Currently the exception
+    # propagates all the way to the top resulting in exit code 1.
+    assert result.ret == 1
 
     result.assert_outcomes(passed=1)
     result.stderr.fnmatch_lines("ValueError: del is broken")
 
 
-@pytest.mark.filterwarnings("default::pytest.PytestUnraisableExceptionWarning")
 def test_create_task_raises_unraisable_warning_filter(pytester: Pytester) -> None:
     # note that the host pytest warning filter is disabled and the pytester
     # warning filter applies during config teardown of unraisablehook.
@@ -306,6 +298,9 @@ def test_create_task_raises_unraisable_warning_filter(pytester: Pytester) -> Non
     # the issue
     pytester.makepyfile(
         test_it="""
+        # Should catch the unraisable exception even if gc is disabled.
+        import gc; gc.disable()
+
         import asyncio
         import pytest
 
@@ -318,11 +313,11 @@ def test_scheduler_must_be_created_within_running_loop() -> None:
         """
     )
 
-    with _disable_gc():
-        result = pytester.runpytest("-Werror")
+    result = pytester.runpytest_subprocess("-Werror")
 
-    # TODO: should be a test failure or error
-    assert result.ret == pytest.ExitCode.INTERNAL_ERROR
+    # TODO: Should be a test failure or error. Currently the exception
+    # propagates all the way to the top resulting in exit code 1.
+    assert result.ret == 1
 
     result.assert_outcomes(passed=1)
     result.stderr.fnmatch_lines("RuntimeWarning: coroutine 'my_task' was never awaited")