pythongh-110932: Fix regrtest for SOURCE_DATE_EPOCH

If the SOURCE_DATE_EPOCH environment variable is defined, use its
value as a string as the random seed.

Lib/test/libregrtest/main.py

@@ -129,14 +129,16 @@ def __init__(self, ns: Namespace, _add_python_opts: bool = False):
 
         # Randomize
         self.randomize: bool = ns.randomize
-        self.random_seed: int | None =  (
-            ns.random_seed
-            if ns.random_seed is not None
-            else random.getrandbits(32)
-        )
         if 'SOURCE_DATE_EPOCH' in os.environ:
             self.randomize = False
-            self.random_seed = None
+            # SOURCE_DATE_EPOCH should be an integer, but use a string to not
+            # fail if it's not integer. random.seed() accepts a string.
+            # https://reproducible-builds.org/docs/source-date-epoch/
+            self.random_seed: int | str = os.environ['SOURCE_DATE_EPOCH']
+        elif ns.random_seed is None:
+            self.random_seed = random.getrandbits(32)
+        else:
+            self.random_seed = ns.random_seed
 
         # tests
         self.first_runtests: RunTests | None = None
@@ -441,7 +443,7 @@ def _run_tests(self, selected: TestTuple, tests: TestList | None) -> int:
                    or tests or self.cmdline_args)):
             display_header(self.use_resources, self.python_cmd)
 
-        print("Using random seed", self.random_seed)
+        print("Using random seed:", self.random_seed)
 
         runtests = self.create_run_tests(selected)
         self.first_runtests = runtests

Lib/test/libregrtest/runtests.py

@@ -91,7 +91,7 @@ class RunTests:
     use_resources: tuple[str, ...]
     python_cmd: tuple[str, ...] | None
     randomize: bool
-    random_seed: int | None
+    random_seed: int | str
     json_file: JsonFile | None
 
     def copy(self, **override):

Lib/test/test_regrtest.py

@@ -149,12 +149,12 @@ def test_randomize(self):
                 self.assertTrue(ns.randomize)
 
         with os_helper.EnvironmentVarGuard() as env:
-            env['SOURCE_DATE_EPOCH'] = '1'
+            env['SOURCE_DATE_EPOCH'] = '1697839080'
 
             ns = self.parse_args(['--randomize'])
             regrtest = main.Regrtest(ns)
             self.assertFalse(regrtest.randomize)
-            self.assertIsNone(regrtest.random_seed)
+            self.assertEqual(regrtest.random_seed, '1697839080')
 
     def test_randseed(self):
         ns = self.parse_args(['--randseed', '12345'])
@@ -388,7 +388,13 @@ def check_ci_mode(self, args, use_resources, rerun=True):
 
         # Check Regrtest attributes which are more reliable than Namespace
         # which has an unclear API
-        regrtest = main.Regrtest(ns)
+        with os_helper.EnvironmentVarGuard() as env:
+            # Ignore SOURCE_DATE_EPOCH env var if it's set
+            if 'SOURCE_DATE_EPOCH' in env:
+                del env['SOURCE_DATE_EPOCH']
+
+            regrtest = main.Regrtest(ns)
+
         self.assertEqual(regrtest.num_workers, -1)
         self.assertEqual(regrtest.want_rerun, rerun)
         self.assertTrue(regrtest.randomize)
@@ -662,7 +668,7 @@ def list_regex(line_format, tests):
         self.check_line(output, f'Result: {state}', full=True)
 
     def parse_random_seed(self, output):
-        match = self.regex_search(r'Using random seed ([0-9]+)', output)
+        match = self.regex_search(r'Using random seed: ([0-9]+)', output)
         randseed = int(match.group(1))
         self.assertTrue(0 <= randseed, randseed)
         return randseed
@@ -672,10 +678,17 @@ def run_command(self, args, input=None, exitcode=0, **kw):
             input = ''
         if 'stderr' not in kw:
             kw['stderr'] = subprocess.STDOUT
+
+        env = kw.pop('env', None)
+        if env is None:
+            env = dict(os.environ)
+            env.pop('SOURCE_DATE_EPOCH', None)
+
         proc = subprocess.run(args,
                               text=True,
                               input=input,
                               stdout=subprocess.PIPE,
+                              env=env,
                               **kw)
         if proc.returncode != exitcode:
             msg = ("Command %s failed with exit code %s, but exit code %s expected!\n"
@@ -955,6 +968,15 @@ def test_random(self):
         output = self.run_tests(test, exitcode=EXITCODE_NO_TESTS_RAN)
         self.assertIsInstance(self.parse_random_seed(output), int)
 
+        # check SOURCE_DATE_EPOCH
+        timestamp = 1697839080
+        env = dict(os.environ, SOURCE_DATE_EPOCH=str(timestamp))
+        output = self.run_tests('-r', test, exitcode=EXITCODE_NO_TESTS_RAN,
+                                env=env)
+        randseed = self.parse_random_seed(output)
+        self.assertEqual(randseed, timestamp)
+        self.check_line(output, 'TESTRANDOM: 520')
+
     def test_fromfile(self):
         # test --fromfile
         tests = [self.create_test() for index in range(5)]

Misc/NEWS.d/next/Tests/2023-10-21-00-10-36.gh-issue-110932.jktjJU.rst

@@ -0,0 +1,3 @@
+Fix regrtest if the ``SOURCE_DATE_EPOCH`` environment variable is defined:
+use the variable value as a string as the random seed. Patch by Victor
+Stinner.