rtutil: Add RTDateTime class.

See comments for rationale.

conservancy_beancount/rtutil.py

@@ -5,6 +5,7 @@
 # Full copyright and licensing details can be found at toplevel file
 # LICENSE.txt in the repository.
 
+import datetime
 import functools
 import logging
 import mimetypes
@@ -13,6 +14,7 @@ import re
 import sqlite3
 import urllib.parse as urlparse
 
+import dateutil.parser
 import rt
 
 from pathlib import Path
@@ -21,6 +23,7 @@ from . import data
 from beancount.core import data as bc_data
 
 from typing import (
+    cast,
     overload,
     Callable,
     Iterable,
@@ -40,6 +43,28 @@ TicketAttachmentIds = Tuple[str, Optional[str]]
 _LinkCache = MutableMapping[TicketAttachmentIds, Optional[str]]
 _URLLookup = Callable[..., Optional[str]]
 
+class RTDateTime(datetime.datetime):
+    """Construct datetime objects from strings returned by RT
+
+    Typical usage looks like::
+
+        ticket = rt_client.get_ticket(...)
+        created = RTDateTime(ticket.get('Created'))
+    """
+    # Normally I'd just write a function to do this, but having a dedicated
+    # class helps support query-report: the class can pull double duty to both
+    # parse the data from RT, and determine proper output formatting.
+    # The RT REST API returns datetimes in the user's configured timezone, and
+    # there doesn't seem to be any API call that tells you what that is. You
+    # have to live with the object being timezone-naive.
+    def __new__(cls, source: str) -> 'RTDateTime':
+        if not source or source == 'Not set':
+            retval = datetime.datetime.min
+        else:
+            retval = dateutil.parser.parse(source)
+        return cast(RTDateTime, retval)
+
+
 class RTLinkCache(_LinkCache):
     """Cache RT links to disk
 

setup.py

@@ -17,6 +17,7 @@ setup(
         # 1.4.1 crashes when trying to save some documents.
         'odfpy>=1.4.0,!=1.4.1',  # Debian:python3-odf
         'pdfminer.six>=20200101',
+        'python-dateutil>=2.7',  # Debian:python3-dateutil
         'PyYAML>=3.0',  # Debian:python3-yaml
         'regex',  # Debian:python3-regex
         'rt>=2.0',

tests/test_rtutil.py

@@ -6,6 +6,7 @@
 # LICENSE.txt in the repository.
 
 import contextlib
+import datetime
 import itertools
 import logging
 import re
@@ -287,3 +288,34 @@ def test_txn_with_urls_with_fmts(rt):
         f'<{DEFAULT_RT_URL}{statement_path}>',
         '[stmt.txt]',
     ])
+
+@pytest.mark.parametrize('arg,exp_num,exp_offset', [
+    # These correspond to the different datetime formats available through
+    # RT's user settings.
+    ('Mon Mar 1 01:01:01 2021', 1, None),
+    ('2021-03-02 02:02:02', 2, None),
+    ('2021-03-03T03:03:03-0500', 3, -18000),
+    ('Thu, 4 Mar 2021 04:04:04 -0600', 4, -21600),
+    ('Fri, 5 Mar 2021 05:05:05 GMT', 5, 0),
+    ('20210306T060606Z', 6, 0),
+    ('Sun, Mar 7, 2021 07:07:07 AM', 7, None),
+    ('Sun, Mar 14, 2021 02:14:14 PM', 14, None),
+])
+def test_rt_datetime(arg, exp_num, exp_offset):
+    actual = rtutil.RTDateTime(arg)
+    assert actual.year == 2021
+    assert actual.month == 3
+    assert actual.day == exp_num
+    assert actual.hour == exp_num
+    assert actual.minute == exp_num
+    assert actual.second == exp_num
+    if exp_offset is None:
+        assert actual.tzinfo is None
+    else:
+        assert actual.tzinfo.utcoffset(None).total_seconds() == exp_offset
+
+@pytest.mark.parametrize('arg', ['Not set', '', None])
+def test_rt_datetime_empty(arg):
+    actual = rtutil.RTDateTime(arg)
+    assert actual == datetime.datetime.min
+    assert actual.tzinfo is None