fix: preserve capture fixture output on thread timeouts

README.rst

@@ -395,6 +395,8 @@ Changelog
 2.5.0
 -----
 
+- Preserve capture-fixture output and disable fixture capturing when reporting
+  thread timeouts. Thanks Arham Begani.
 - Fix fixture teardowns not timing out after failed tests. Thanks Timofey Peshin.
 - Add ruff and typos linters, drop black/isort/flake8 linters. Thanks Vladimir Roshchin.
 - Minimum support Python3.10 and pytest=8.0. Thanks Vladimir Roshchin.

pytest_timeout.py

@@ -15,6 +15,7 @@
 import time
 import traceback
 from collections import namedtuple
+from contextlib import ExitStack
 
 import pytest
 
@@ -498,41 +499,45 @@ def timeout_sigalrm(item, settings):
 def timeout_timer(item, settings):
     """Dump stack of threads and call os._exit().
 
-    This disables the capturemanager and dumps stdout and stderr.
+    This disables global and fixture capturing and dumps stdout and stderr.
     Then the stacks are dumped and os._exit(1) is called.
     """
     if not settings.disable_debugger_detection and is_debugging():
         return
     terminal = item.config.get_terminal_writer()
-    try:
-        capman = item.config.pluginmanager.getplugin("capturemanager")
-        if capman:
-            capman.suspend_global_capture(item)
-            stdout, stderr = capman.read_global_capture()
-        else:
-            stdout, stderr = None, None
-        terminal.sep("+", title="Timeout")
-        caplog = item.config.pluginmanager.getplugin("_capturelog")
-        if caplog and hasattr(item, "capturelog_handler"):
-            log = item.capturelog_handler.stream.getvalue()
-            if log:
-                terminal.sep("~", title="Captured log")
-                terminal.write(log)
-        if stdout:
-            terminal.sep("~", title="Captured stdout")
-            terminal.write(stdout)
-        if stderr:
-            terminal.sep("~", title="Captured stderr")
-            terminal.write(stderr)
-        dump_stacks(terminal)
-        terminal.sep("+", title="Timeout")
-    except Exception:
-        traceback.print_exc()
-    finally:
-        terminal.flush()
-        sys.stdout.flush()
-        sys.stderr.flush()
-        os._exit(1)
+    with ExitStack() as stack:
+        try:
+            capman = item.config.pluginmanager.getplugin("capturemanager")
+            if capman:
+                # Flush fixture buffers into global capture before reading it.
+                # No test or fixture teardown will run after os._exit below.
+                capman.deactivate_fixture()
+                stack.enter_context(capman.global_and_fixture_disabled())
+                stdout, stderr = capman.read_global_capture()
+            else:
+                stdout, stderr = None, None
+            terminal.sep("+", title="Timeout")
+            caplog = item.config.pluginmanager.getplugin("_capturelog")
+            if caplog and hasattr(item, "capturelog_handler"):
+                log = item.capturelog_handler.stream.getvalue()
+                if log:
+                    terminal.sep("~", title="Captured log")
+                    terminal.write(log)
+            if stdout:
+                terminal.sep("~", title="Captured stdout")
+                terminal.write(stdout)
+            if stderr:
+                terminal.sep("~", title="Captured stderr")
+                terminal.write(stderr)
+            dump_stacks(terminal)
+            terminal.sep("+", title="Timeout")
+        except Exception:
+            traceback.print_exc()
+        finally:
+            terminal.flush()
+            sys.stdout.flush()
+            sys.stderr.flush()
+            os._exit(1)
 
 
 def dump_stacks(terminal):

test_pytest_timeout.py

@@ -71,6 +71,54 @@ def test_foo():
     assert "++ Timeout ++" in result.stdout.lines[-1]
 
 
+@pytest.mark.parametrize("capture", ["fd", "no"])
+@pytest.mark.parametrize("fixture", ["capsys", "capfd", "capsysbinary", "capfdbinary"])
+def test_thread_with_capture_fixture(pytester, capture, fixture):
+    pytester.makepyfile(
+        f"""
+        import sys
+        import time
+
+        def test_foo({fixture}):
+            print("FIXTURE STDOUT")
+            print("FIXTURE STDERR", file=sys.stderr)
+            time.sleep(10)
+        """
+    )
+
+    result = pytester.runpytest_subprocess(
+        "--timeout=1", "--timeout-method=thread", f"--capture={capture}", timeout=20
+    )
+
+    assert result.ret == 1
+    assert any(line.endswith("FIXTURE STDOUT") for line in result.stdout.lines)
+    assert any(
+        line.endswith("FIXTURE STDERR")
+        for line in result.stdout.lines + result.stderr.lines
+    )
+    result.stdout.fnmatch_lines(["*++ Timeout ++*", "*~~ Stack of MainThread* ~~*"])
+
+
+def test_thread_without_capture_plugin(pytester):
+    pytester.makepyfile(
+        """
+        import time
+
+        def test_foo():
+            print("UNCAPTURED STDOUT", flush=True)
+            time.sleep(10)
+        """
+    )
+
+    result = pytester.runpytest_subprocess(
+        "--timeout=1", "--timeout-method=thread", "-p", "no:capture", timeout=20
+    )
+
+    assert result.ret == 1
+    assert any(line.endswith("UNCAPTURED STDOUT") for line in result.stdout.lines)
+    result.stdout.fnmatch_lines(["*++ Timeout ++*", "*~~ Stack of MainThread* ~~*"])
+
+
 def test_cov(pytester):
     # This test requires pytest-cov
     pytest.importorskip("pytest_cov")