Issue #28950: Disallow -j0 combined with -T/-l/-M in regrtest.

Lib/test/regrtest.py

@@ -380,11 +380,11 @@ def _parse_args(args, **kwargs):
 
     if ns.single and ns.fromfile:
         parser.error("-s and -f don't go together!")
-    if ns.use_mp and ns.trace:
+    if ns.use_mp is not None and ns.trace:
         parser.error("-T and -j don't go together!")
-    if ns.use_mp and ns.findleaks:
+    if ns.use_mp is not None and ns.findleaks:
         parser.error("-l and -j don't go together!")
-    if ns.use_mp and ns.memlimit:
+    if ns.use_mp is not None and ns.memlimit:
         parser.error("-M and -j don't go together!")
     if ns.failfast and not (ns.verbose or ns.verbose3):
         parser.error("-G/--failfast needs either -v or -W")

Lib/test/test_regrtest.py

@@ -200,6 +200,9 @@ class ParseArgsTestCase(unittest.TestCase):
                 self.checkError([opt, '2', '-T'], "don't go together")
                 self.checkError([opt, '2', '-l'], "don't go together")
                 self.checkError([opt, '2', '-M', '4G'], "don't go together")
+                self.checkError([opt, '0', '-T'], "don't go together")
+                self.checkError([opt, '0', '-l'], "don't go together")
+                self.checkError([opt, '0', '-M', '4G'], "don't go together")
 
     def test_coverage(self):
         for opt in '-T', '--coverage':

Misc/NEWS

@@ -549,6 +549,9 @@ Documentation
 Tests
 -----
 
+- Issue #28950: Disallow -j0 to be combined with -T/-l/-M in regrtest
+  command line arguments.
+
 - Issue #28666: Now test.support.rmtree is able to remove unwritable or
   unreadable directories.