to_datetime fails with negative fractional timestamps

[Jun Omae]

make test failed with CentOS 5.5 and Python 2.4.3.

======================================================================
ERROR: test_to_datetime_microsecond_negative_timestamps (trac.util.tests.datefmt.DateFormatTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/jun66j5/src/trac.git/trac/util/tests/datefmt.py", line 76, in test_to_datetime_microsecond_negative_timestamps
    datefmt.localtz)
ValueError: microsecond must be in 0..999999

----------------------------------------------------------------------
Ran 1103 tests in 47.497s

FAILED (errors=1)
make: *** [unit-test] Error 1

The issue is known bug of Python 2.4. cf. ​Issue 1646728: datetime.fromtimestamp fails with negative fractional times - Python tracker

Created the patch with the helps of it.

trac/util/datefmt.py

@@ -18 +18 @@
 #         Matthew Good <trac@matt-good.net>
 
 import locale
+import math
 import re
 import sys
 import time
-from datetime import tzinfo, timedelta, datetime, date
+from datetime import tzinfo, timedelta, datetime, date, timedelta
 
 from trac.core import TracError
 from trac.util.text import to_unicode
@@ -52 +53 @@
         if not (_min_ts <= t <= _max_ts):
             # Handle microsecond timestamps for 0.11 compatibility
             t = t * 0.000001
+        if t < 0:
+            # negative fractional times bug
+            # http://bugs.python.org/issue1646728
+            integer = math.floor(t)
+            frac = t - integer
+            return datetime.fromtimestamp(integer, tzinfo or localtz) \
+                   + timedelta(seconds=frac)
         return datetime.fromtimestamp(t, tzinfo or localtz)
     raise TypeError('expecting datetime, int, long, float, or None; got %s' %
                     type(t))

trac/util/tests/datefmt.py

@@ -72 +72 @@
         self.assertEqual(datefmt.to_datetime(2345678912.0), expected)
 
     def test_to_datetime_microsecond_negative_timestamps(self):
-        expected = datetime.datetime.fromtimestamp(-2345.678912,
-                                                   datefmt.localtz)
+        expected = datetime.datetime.fromtimestamp(-2345, datefmt.localtz) \
+                   - datetime.timedelta(seconds=.678912)
+
+        self.assertEqual(datefmt.to_datetime(-2345678912).microsecond,
+                         321088) # 1000000 - 678912
         self.assertEqual(datefmt.to_datetime(-2345678912), expected)
         self.assertEqual(datefmt.to_datetime(-2345678912L), expected)
         self.assertEqual(datefmt.to_datetime(-2345678912.0), expected)

[Remy Blank]

Slightly simpler patch applied in [9855]. Thanks!