[Python-checkins] gh-94675: Add a regression test for rjsmin re slowdown (GH-94685)

[gpshead]

https://github.com/python/cpython/commit/fe23c0061d9c72527ad57a8c965d8161b00f500e
commit: fe23c0061d9c72527ad57a8c965d8161b00f500e
branch: main
author: Miro Hrončok <miro at hroncok.cz>
committer: gpshead <greg at krypto.org>
date: 2022-08-03T16:19:36-07:00
summary:

gh-94675: Add a regression test for rjsmin re slowdown (GH-94685)

Adds a regression test for an re slowdown observed by rjsmin.
Uses multiprocessing to kill the test after SHORT_TIMEOUT.

Co-authored-by: Oleg Iarygin <dralife at yandex.ru>
Co-authored-by: Christian Heimes <christian at python.org>

files:
A Misc/NEWS.d/next/Tests/2022-07-08-12-22-00.gh-issue-94675.IiTs5f.rst
M Lib/test/test_re.py

diff --git a/Lib/test/test_re.py b/Lib/test/test_re.py
index 9f734d47c54..3f0f84ea8ce 100644
--- a/Lib/test/test_re.py
+++ b/Lib/test/test_re.py
@@ -1,6 +1,7 @@
 from test.support import (gc_collect, bigmemtest, _2G,
                           cpython_only, captured_stdout,
-                          check_disallow_instantiation, is_emscripten, is_wasi)
+                          check_disallow_instantiation, is_emscripten, is_wasi,
+                          SHORT_TIMEOUT)
 import locale
 import re
 import string
@@ -11,6 +12,14 @@
 from re import Scanner
 from weakref import proxy
 
+# some platforms lack working multiprocessing
+try:
+    import _multiprocessing
+except ImportError:
+    multiprocessing = None
+else:
+    import multiprocessing
+
 # Misc tests from Tim Peters' re.doc
 
 # WARNING: Don't change details in these tests if you don't know
@@ -2407,6 +2416,26 @@ def test_template_function_and_flag_is_deprecated(self):
         self.assertTrue(template_re1.match('ahoy'))
         self.assertFalse(template_re1.match('nope'))
 
+    @unittest.skipIf(multiprocessing is None, 'test requires multiprocessing')
+    def test_regression_gh94675(self):
+        pattern = re.compile(r'(?<=[({}])(((//[^\n]*)?[\n])([\000-\040])*)*'
+                             r'((/[^/\[\n]*(([^\n]|(\[\n]*(]*)*\]))'
+                             r'[^/\[]*)*/))((((//[^\n]*)?[\n])'
+                             r'([\000-\040]|(/\*[^*]*\*+'
+                             r'([^/*]\*+)*/))*)+(?=[^\000-\040);\]}]))')
+        input_js = '''a(function() {
+            ///////////////////////////////////////////////////////////////////
+        });'''
+        p = multiprocessing.Process(target=pattern.sub, args=('', input_js))
+        p.start()
+        p.join(SHORT_TIMEOUT)
+        try:
+            self.assertFalse(p.is_alive(), 'pattern.sub() timed out')
+        finally:
+            if p.is_alive():
+                p.terminate()
+                p.join()
+
 
 def get_debug_out(pat):
     with captured_stdout() as out:
diff --git a/Misc/NEWS.d/next/Tests/2022-07-08-12-22-00.gh-issue-94675.IiTs5f.rst b/Misc/NEWS.d/next/Tests/2022-07-08-12-22-00.gh-issue-94675.IiTs5f.rst
new file mode 100644
index 00000000000..d0005d9f601
--- /dev/null
+++ b/Misc/NEWS.d/next/Tests/2022-07-08-12-22-00.gh-issue-94675.IiTs5f.rst
@@ -0,0 +1 @@
+Add a regression test for :mod:`re` exponentional slowdown when using rjsmin.