Fix: Improve RFC3339 date parsing validation (Issue kubernetes-client#2418)

- Replace search() with fullmatch() for strict RFC3339 format validation
- Provide clear, actionable error messages with expected format
- Add input whitespace stripping before validation
- Improve exception handling with specific ValueError messages
- Add comprehensive test cases for invalid formats
- Addresses reviewer feedback from PR kubernetes-client#2420

Test: Existing tests pass + new test cases added

Author: Naman-cell

kubernetes/base/config/dateutil.py

@@ -49,18 +49,27 @@ def dst(self, dt):
 
 def parse_rfc3339(s):
     if isinstance(s, datetime.datetime):
-        # no need to parse it, just make sure it has a timezone.
         if not s.tzinfo:
             return s.replace(tzinfo=UTC)
         return s
-    groups = _re_rfc3339.search(s).groups()
+    
+    m = _re_rfc3339.fullmatch(s.strip())
+    if m is None:
+        raise ValueError(
+            f"Invalid RFC3339 datetime: {s!r} "
+            "(expected YYYY-MM-DDTHH:MM:SS[.frac][Z|±HH:MM])"
+        )
+    
+    groups = m.groups()
     dt = [0] * 7
     for x in range(6):
         dt[x] = int(groups[x])
+    
     us = 0
     if groups[6] is not None:
         partial_sec = float(groups[6].replace(",", "."))
         us = int(MICROSEC_PER_SEC * partial_sec)
+    
     tz = UTC
     if groups[7] is not None and groups[7] != 'Z' and groups[7] != 'z':
         tz_groups = _re_timezone.search(groups[7]).groups()
@@ -71,10 +80,17 @@ def parse_rfc3339(s):
         if tz_groups[2]:
             minute = int(tz_groups[2])
         tz = TimezoneInfo(hour, minute)
-    return datetime.datetime(
-        year=dt[0], month=dt[1], day=dt[2],
-        hour=dt[3], minute=dt[4], second=dt[5],
-        microsecond=us, tzinfo=tz)
+    
+    try:
+        return datetime.datetime(
+            year=dt[0], month=dt[1], day=dt[2],
+            hour=dt[3], minute=dt[4], second=dt[5],
+            microsecond=us, tzinfo=tz)
+    except ValueError as e:
+        raise ValueError(
+            f"Invalid date/time values in RFC3339 string {s!r}: {e}"
+        ) from e
+
 
 
 def format_rfc3339(date_time):

kubernetes/base/config/dateutil_test.py

@@ -66,3 +66,39 @@ def test_format_rfc3339(self):
             format_rfc3339(datetime(2017, 7, 25, 4, 44, 21, 0,
                                     TimezoneInfo(-2, 30))),
             "2017-07-25T07:14:21Z")
+
+    def test_parse_rfc3339_invalid_formats(self):
+        """Test that invalid RFC3339 formats raise ValueError"""
+        invalid_inputs = [
+            "2025-13-02T13:37:00Z",        # Invalid month
+            "2025-12-32T13:37:00Z",        # Invalid day
+            "2025-12-02T25:00:00Z",        # Invalid hour
+            "2025-12-02T13:60:00Z",        # Invalid minute
+            "2025-12-02T13:37:60Z",        # Invalid second
+            "not-a-valid-date",            # Completely invalid
+            "",                             # Empty string
+            "2025-12-02Z13:37:00",         # Timezone before time
+        ]
+
+        for invalid_input in invalid_inputs:
+            with self.assertRaises(ValueError):
+                parse_rfc3339(invalid_input)
+
+
+
+    def test_parse_rfc3339_with_whitespace(self):
+        """Test that leading/trailing whitespace is handled"""
+        actual = parse_rfc3339("  2017-07-25T04:44:21Z  ")
+        expected = datetime(2017, 7, 25, 4, 44, 21, 0, UTC)
+        self.assertEqual(expected, actual)
+
+    def test_parse_rfc3339_error_message_clarity(self):
+        """Test that error messages are clear and helpful"""
+        try:
+            parse_rfc3339("invalid-date-format")
+        except ValueError as e:
+            error_msg = str(e)
+            # Verify error message contains helpful information
+            self.assertIn("Invalid RFC3339", error_msg)
+            self.assertIn("YYYY-MM-DD", error_msg)
+            self.assertIn("expected", error_msg)