From 00c18dae5d5e236c9394be890d457f58aeee624c Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Tue, 31 Oct 2023 22:05:46 +0100
Subject: [PATCH] gh-110367: Make regrtest --verbose3 compatible with
 --huntrleaks -jN

"./python -m test -j1 -R 3:3 --verbose3" now works as expected, since
run_single_test() does not replace sys.stdout with StringIO in this
case.
---
 Lib/test/libregrtest/cmdline.py               | 10 +++++++--
 Lib/test/test_regrtest.py                     | 21 +++++++++++++++++++
 ...-10-31-22-09-25.gh-issue-110367.UhQi44.rst |  3 +++
 3 files changed, 32 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Tests/2023-10-31-22-09-25.gh-issue-110367.UhQi44.rst

diff --git a/Lib/test/libregrtest/cmdline.py b/Lib/test/libregrtest/cmdline.py
index 87b926db0686cec..1747511b57cc52a 100644
--- a/Lib/test/libregrtest/cmdline.py
+++ b/Lib/test/libregrtest/cmdline.py
@@ -493,10 +493,16 @@ def _parse_args(args, **kwargs):
         ns.randomize = True
     if ns.verbose:
         ns.header = True
-    if ns.huntrleaks and ns.verbose3:
+    # When -jN option is used, a worker process does not use --verbose3
+    # and so -R 3:3 -jN --verbose3 just works as expected: there is no false
+    # alarm about memory leak.
+    if ns.huntrleaks and ns.verbose3 and ns.use_mp is None:
         ns.verbose3 = False
+        # run_single_test() replaces sys.stdout with io.StringIO if verbose3
+        # is true. In this case, huntrleaks sees an write into StringIO as
+        # a memory leak, whereas it is not (gh-71290).
         print("WARNING: Disable --verbose3 because it's incompatible with "
-              "--huntrleaks: see http://bugs.python.org/issue27103",
+              "--huntrleaks without -jN option",
               file=sys.stderr)
     if ns.forever:
         # --forever implies --failfast
diff --git a/Lib/test/test_regrtest.py b/Lib/test/test_regrtest.py
index 0c39af05eb5ea8b..77b964f731c53e3 100644
--- a/Lib/test/test_regrtest.py
+++ b/Lib/test/test_regrtest.py
@@ -2120,6 +2120,27 @@ def test_crash(self):
             self.assertIn(f"Exit code {exitcode} (SIGSEGV)", output)
         self.check_line(output, "just before crash!", full=True, regex=False)
 
+    def test_verbose3(self):
+        code = textwrap.dedent(r"""
+            import unittest
+            from test import support
+
+            class VerboseTests(unittest.TestCase):
+                def test_pass(self):
+                    print("SPAM SPAM SPAM")
+        """)
+        testname = self.create_test(code=code)
+
+        # Run sequentially
+        output = self.run_tests("--verbose3", testname)
+        self.check_executed_tests(output, testname, stats=1)
+        self.assertNotIn('SPAM SPAM SPAM', output)
+
+        # Check for reference leaks, run in parallel
+        output = self.run_tests("-R", "3:3", "-j1", "--verbose3", testname)
+        self.check_executed_tests(output, testname, stats=1, parallel=True)
+        self.assertNotIn('SPAM SPAM SPAM', output)
+
 
 class TestUtils(unittest.TestCase):
     def test_format_duration(self):
diff --git a/Misc/NEWS.d/next/Tests/2023-10-31-22-09-25.gh-issue-110367.UhQi44.rst b/Misc/NEWS.d/next/Tests/2023-10-31-22-09-25.gh-issue-110367.UhQi44.rst
new file mode 100644
index 000000000000000..70119e73d860301
--- /dev/null
+++ b/Misc/NEWS.d/next/Tests/2023-10-31-22-09-25.gh-issue-110367.UhQi44.rst
@@ -0,0 +1,3 @@
+Make regrtest ``--verbose3`` compatible with ``--huntrleaks -jN``. The
+``./python -m test -j1 -R 3:3 --verbose3`` command now works as expected. Patch
+by Victor Stinner.