[mythtv-commits] Ticket #13299: Python Bindings fail to calculate date-time object

[MythTV]

#13299: Python Bindings fail to calculate date-time object
-------------------------------+--------------------------------
 Reporter:  rcrdnalor          |          Owner:  Raymond Wagner
     Type:  Patch - Bug Fix    |         Status:  new
 Priority:  minor              |      Milestone:  needs_triage
Component:  Bindings - Python  |        Version:  Unspecified
 Severity:  medium             |     Resolution:
 Keywords:                     |  Ticket locked:  0
-------------------------------+--------------------------------

Comment (by rcrdnalor):

 Replying to [comment:6 rcrdnalor]:
 > I am fine with the patch "0001-python-Handle-massively-negative-initial-
 zoneinfo-en.patch".
 > I tested successfully all proposed patches with the timezone-info for
 ubuntu (trusty, bionic) and debian (jessie, stretch, sid) in respect to
 the time zomes 'Europe/Vienna' and 'Antartica/Macquarie'. The latter one
 is known to be problematic in the mailing lists of 'iana.org/time-zones'.
 >

 Unfortunately, I spoke to soon:
 With the applied patch '0001-python-Handle-massively-negative-initial-
 zoneinfo-en.patch',
 MythTV Python Bindings cannot load timezone files containing no
 transitions or no modern transitions.
 Those timezones are of type 'UTC' or 'GMT+x'.
 On import of the 'datetime' module, MythTV python fails to create a
 posixtzinfo for 'UTC'.

 Procedure to show the error:
 On fixes/30 or master, if you change the MythTV's Python Bindings utility
 'datetime' to raise an error upon this, like in the following snippet:

 {{{
 file utility/datetime.py

     @classmethod
     def UTCTZ(cls):
         try:
             return posixtzinfo('Etc/UTC')
         except:
             raise
             # return offsettzinfo()
 }}}

 You will get the traceback like this when you import datetime from MythTV:

 {{{
 $ python2

 >>> from MythTV import datetime
 Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
   File "MythTV/__init__.py", line 41, in <module>
     from .dataheap import *
   File "MythTV/dataheap.py", line 20, in <module>
     _default_datetime = datetime(1900,1,1, tzinfo=datetime.UTCTZ())
   File "MythTV/utility/dt.py", line 290, in UTCTZ
     return posixtzinfo('Etc/UTC')
   File "MythTV/utility/singleton.py", line 49, in __call__
     inst = type.__call__(cls, *args, **kwargs)
   File "MythTV/utility/dt.py", line 230, in __init__
     self._process(fd, version)
   File "MythTV/utility/dt.py", line 193, in _process
     for i in range(first_modern_transition, counts.transitions):
 TypeError: range() integer start argument expected, got NoneType.
 }}}

 This can be verified by (without the code change):

 {{{
 $ python2

 >>> from MythTV import datetime
 >>>
 >>> datetime.now()
 datetime(2019, 5, 9, 19, 48, 55, 765719,
 tzinfo=<MythTV.utility.dt.posixtzinfo object at 0x7fa41d8a4150>)
 >>>
 >>> datetime.utcnow()
 datetime(2019, 5, 9, 17, 49, 8, 21672,
 tzinfo=<MythTV.utility.dt.offsettzinfo object at 0x7fa4251970d0>)
 }}}

 Note the 'posixtzinfo' reference for local time-zone and the
 'offsettzinfo' reference to the UTC time-zone.

 This shows, that the Python Bindings do not load the posix zonefile for
 'UTC' in a correct way.
 Expected output is (with applied additional patches attached to this
 ticket):

 {{{
 $ python2

 >>> from MythTV import datetime
 >>>
 >>> datetime.now()
 datetime(2019, 5, 9, 19, 56, 16, 232801,
 tzinfo=<MythTV.utility.dt.posixtzinfo object at 0x7febb282c150>)
 >>>
 >>> datetime.utcnow()
 datetime(2019, 5, 9, 17, 56, 28, 960914,
 tzinfo=<MythTV.utility.dt.posixtzinfo object at 0x7febb2812ad0>)
 >>>
 }}}

 The attached patches handle the corner cases where the zone-info files
 have no 'modern transitions' or no transitions at all.
 This is valid for timezones of type 'UTC' or 'GMT+x'.
 With these patches applied, I get the expected datetime object with
 'posixtzinfo' as 'tzinfo' object.
 Note: The 'offsettzinfo' object only provides a simple static offset to
 the timezone. Therefore the 'posixtzinfo' method is the preferred method.

 Attached patches for fixes/30 and master and for fixes/29.

-- 
Ticket URL: <https://code.mythtv.org/trac/ticket/13299#comment:14>
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