[3.14] gh-154427: Check the access time in UtimeTests only if it is stored (GH-154428...

HAMMER2 on DragonFly BSD does not store the access time and os.stat()
returns the modification time instead.  Probe the file system, like it
is already done for the timestamp resolution.
(cherry picked from commit 6f8f97fe5246837b93e6c2f3525aa9f623ecd30b)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 6a2efed3b1d0ae1da6059ce9d8630b4305cbfc80..3942877215f53ea84e0fbcfc6e44261dde0f56f9 100644 (file)
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -899,11 +899,18 @@ class UtimeTests(unittest.TestCase):
                 or (st.st_mtime != st[8])
                 or (st.st_ctime != st[9]))
 
+    def support_atime(self, filename):
+        # Heuristic to check if the filesystem stores the access time.
+        # Use whole seconds, to not depend on the timestamp resolution.
+        os.utime(filename, (1, 2))
+        return os.stat(filename).st_atime == 1
+
     def _test_utime(self, set_time, filename=None):
         if not filename:
             filename = self.fname
 
         support_subsecond = self.support_subsecond(filename)
+        support_atime = self.support_atime(filename)
         if support_subsecond:
             # Timestamp with a resolution of 1 microsecond (10^-6).
             #
@@ -930,18 +937,22 @@ class UtimeTests(unittest.TestCase):
             # digits worth of sub-second precision.
             # Some day it would be good to fix this upstream.
             delta=1e-5
-            self.assertAlmostEqual(st.st_atime, atime_ns * 1e-9, delta=1e-5)
+            if support_atime:
+                self.assertAlmostEqual(st.st_atime, atime_ns * 1e-9, delta=1e-5)
+                self.assertAlmostEqual(st.st_atime_ns, atime_ns, delta=1e9 * 1e-5)
             self.assertAlmostEqual(st.st_mtime, mtime_ns * 1e-9, delta=1e-5)
-            self.assertAlmostEqual(st.st_atime_ns, atime_ns, delta=1e9 * 1e-5)
             self.assertAlmostEqual(st.st_mtime_ns, mtime_ns, delta=1e9 * 1e-5)
         else:
             if support_subsecond:
-                self.assertAlmostEqual(st.st_atime, atime_ns * 1e-9, delta=1e-6)
+                if support_atime:
+                    self.assertAlmostEqual(st.st_atime, atime_ns * 1e-9, delta=1e-6)
                 self.assertAlmostEqual(st.st_mtime, mtime_ns * 1e-9, delta=1e-6)
             else:
-                self.assertEqual(st.st_atime, atime_ns * 1e-9)
+                if support_atime:
+                    self.assertEqual(st.st_atime, atime_ns * 1e-9)
                 self.assertEqual(st.st_mtime, mtime_ns * 1e-9)
-            self.assertEqual(st.st_atime_ns, atime_ns)
+            if support_atime:
+                self.assertEqual(st.st_atime_ns, atime_ns)
             self.assertEqual(st.st_mtime_ns, mtime_ns)
 
     def test_utime(self):