msgpack: support tzindex in datetime

Support non-zero tzindex in datetime extended type. If both tzoffset and
tzindex are specified, tzindex is prior (same as in Tarantool [1]).

Use `tz` parameter to set up timezone name:

```
dt = tarantool.Datetime(year=2022, month=8, day=31,
                        hour=18, minute=7, sec=54,
                        nsec=308543321, tz='Europe/Moscow')
```

You may use `tz` property to get timezone name of a datetime object.

pytz is used to build timezone info. Tarantool index to Olson name
map and inverted one are built with gen_timezones.sh script based on
tarantool/go-tarantool script [2]. All Tarantool unique and alias
timezones presents in pytz.all_timezones list. Only the following
abrreviated timezones from Tarantool presents in pytz.all_timezones
(version 2022.2.1):
- CET
- EET
- EST
- GMT
- HST
- MST
- UTC
- WET

pytz does not natively support work with abbreviated timezones due to
its possibly ambiguous nature [3-5]. Tarantool itself do not support
work with ambiguous abbreviated timezones:

```
Tarantool 2.10.1-0-g482d91c66

tarantool> datetime.new({tz = 'BST'})
---
- error: 'builtin/datetime.lua:477: could not parse ''BST'' - ambiguous timezone'
...
```
If ambiguous timezone is specified, the exception is raised.

Tarantool header timezones.h [6] provides a map for all abbreviated
timezones with category info (all ambiguous timezones are marked with
TZ_AMBIGUOUS flag) and offset info. We parse this info to build
pytz.FixedOffset() timezone for each Tarantool abbreviated timezone not
supported natively by pytz.

1. https://www.tarantool.io/en/doc/latest/reference/reference_lua/datetime/new/
2. https://github.com/tarantool/go-tarantool/blob/5801dc6f5ce69db7c8bc0c0d0fe4fb6042d5ecbc/datetime/gen-timezones.sh
3. https://stackoverflow.com/questions/37109945/how-to-use-abbreviated-timezone-namepst-ist-in-pytz
4. https://stackoverflow.com/questions/27531718/datetime-timezone-conversion-using-pytz
5. https://stackoverflow.com/questions/30315485/pytz-return-olson-timezone-name-from-only-a-gmt-offset
6. https://github.com/tarantool/tarantool/9ee45289e01232b8df1413efea11db170ae3b3b4/src/lib/tzcode/timezones.h

Closes #204

Author: DifferentialOrange

CHANGELOG.md

@@ -53,6 +53,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   You may use `tzoffset` property to get timezone offset of a datetime
   object.
 
+- Timezone in datetime type support (#204).
+
+  Use `tz` parameter to set up timezone name:
+
+  ```python
+  dt = tarantool.Datetime(year=2022, month=8, day=31,
+                          hour=18, minute=7, sec=54,
+                          nsec=308543321, tz='Europe/Moscow')
+  ```
+
+  If both `tz` and `tzoffset` is specified, `tz` is used.
+
+  You may use `tz` property to get timezone name of a datetime object.
+
 ### Changed
 - Bump msgpack requirement to 1.0.4 (PR #223).
   The only reason of this bump is various vulnerability fixes,

tarantool/msgpack_ext/types/datetime.py

@@ -3,6 +3,9 @@
 import pandas
 import pytz
 
+import tarantool.msgpack_ext.types.timezones as tt_timezones
+from tarantool.error import MsgpackError
+
 # https://www.tarantool.io/en/doc/latest/dev_guide/internals/msgpack_extensions/#the-datetime-type
 #
 # The datetime MessagePack representation looks like this:
@@ -63,6 +66,17 @@ def compute_offset(timestamp):
     # There is no precision loss since offset is in minutes
     return int(utc_offset.total_seconds()) // SEC_IN_MIN
 
+def get_python_tzinfo(tz, error_class):
+    if tz in pytz.all_timezones:
+        return pytz.timezone(tz)
+
+    # Checked with timezones/validate_timezones.py
+    tt_tzinfo = tt_timezones.timezoneAbbrevInfo[tz]
+    if (tt_tzinfo['category'] & tt_timezones.TZ_AMBIGUOUS) != 0:
+        raise error_class(f'Failed to create datetime with ambiguous timezone "{tz}"')
+
+    return pytz.FixedOffset(tt_tzinfo['offset'])
+
 def msgpack_decode(data):
     cursor = 0
     seconds, cursor = get_bytes_as_int(data, cursor, SECONDS_SIZE_BYTES)
@@ -84,23 +98,29 @@ def msgpack_decode(data):
     datetime = pandas.to_datetime(total_nsec, unit='ns')
 
     if tzindex != 0:
-        raise NotImplementedError
+        if tzindex not in tt_timezones.indexToTimezone:
+            raise MsgpackError(f'Failed to decode datetime with unknown tzindex "{tzindex}"')
+        tz = tt_timezones.indexToTimezone[tzindex]
+        tzinfo = get_python_tzinfo(tz, MsgpackError)
+        return datetime.replace(tzinfo=pytz.UTC).tz_convert(tzinfo), tz
     elif tzoffset != 0:
         tzinfo = pytz.FixedOffset(tzoffset)
-        return datetime.replace(tzinfo=pytz.UTC).tz_convert(tzinfo)
+        return datetime.replace(tzinfo=pytz.UTC).tz_convert(tzinfo), ''
     else:
-        return datetime
+        return datetime, ''
 
 class Datetime():
     def __init__(self, data=None, *, timestamp=None, year=None, month=None,
                  day=None, hour=None, minute=None, sec=None, nsec=None,
-                 tzoffset=0):
+                 tzoffset=0, tz=''):
         if data is not None:
             if not isinstance(data, bytes):
                 raise ValueError('data argument (first positional argument) ' +
                                  'expected to be a "bytes" instance')
 
-            self._datetime = msgpack_decode(data)
+            datetime, tz = msgpack_decode(data)
+            self._datetime = datetime
+            self._tz = tz
             return
 
         # The logic is same as in Tarantool, refer to datetime API.
@@ -133,11 +153,20 @@ def __init__(self, data=None, *, timestamp=None, year=None, month=None,
                                         microsecond=microsecond,
                                         nanosecond=nanosecond)
 
-        if tzoffset != 0:
-            tzinfo = pytz.FixedOffset(tzoffset)
-            datetime = datetime.replace(tzinfo=tzinfo)
+        if tz != '':
+            if tz not in tt_timezones.timezoneToIndex:
+                raise ValueError(f'Unknown Tarantool timezone "{tz}"')
 
-        self._datetime = datetime
+            tzinfo = get_python_tzinfo(tz, ValueError)
+            self._datetime = datetime.replace(tzinfo=tzinfo)
+            self._tz = tz
+        elif tzoffset != 0:
+            tzinfo = pytz.FixedOffset(tzoffset)
+            self._datetime = datetime.replace(tzinfo=tzinfo)
+            self._tz = ''
+        else:
+            self._datetime = datetime
+            self._tz = ''
 
     def __eq__(self, other):
         if isinstance(other, Datetime):
@@ -151,7 +180,7 @@ def __str__(self):
         return self._datetime.__str__()
 
     def __repr__(self):
-        return f'datetime: {self._datetime.__repr__()}'
+        return f'datetime: {self._datetime.__repr__()}, tz: "{self.tz}"'
 
     def __copy__(self):
         cls = self.__class__
@@ -206,11 +235,20 @@ def tzoffset(self):
             return compute_offset(self._datetime)
         return 0
 
+    @property
+    def tz(self):
+        return self._tz
+
     def msgpack_encode(self):
         seconds = self._datetime.value // NSEC_IN_SEC
         nsec = self.nsec
         tzoffset = self.tzoffset
-        tzindex = 0
+
+        tz = self.tz
+        if tz != '':
+            tzindex = tt_timezones.timezoneToIndex[tz]
+        else:
+            tzindex = 0
 
         buf = get_int_as_bytes(seconds, SECONDS_SIZE_BYTES)
 

tarantool/msgpack_ext/types/timezones/__init__.py

@@ -0,0 +1,9 @@
+from tarantool.msgpack_ext.types.timezones.timezones import (
+	TZ_AMBIGUOUS,
+	indexToTimezone,
+	timezoneToIndex,
+	timezoneAbbrevInfo,
+)
+
+__all__ = ['TZ_AMBIGUOUS', 'indexToTimezone', 'timezoneToIndex',
+           'timezoneAbbrevInfo']

tarantool/msgpack_ext/types/timezones/gen-timezones.sh

@@ -0,0 +1,69 @@
+#!/usr/bin/env bash
+set -xeuo pipefail
+
+SRC_COMMIT="9ee45289e01232b8df1413efea11db170ae3b3b4"
+SRC_FILE=timezones.h
+DST_FILE=timezones.py
+
+[ -e ${SRC_FILE} ] && rm ${SRC_FILE}
+wget -O ${SRC_FILE} \
+	https://raw.githubusercontent.com/tarantool/tarantool/${SRC_COMMIT}/src/lib/tzcode/timezones.h
+
+# We don't need aliases in indexToTimezone because Tarantool always replace it:
+#
+# tarantool> T = date.parse '2022-01-01T00:00 Pacific/Enderbury'
+# ---
+# ...
+# tarantool> T
+# ---
+# - 2022-01-01T00:00:00 Pacific/Kanton
+# ...
+#
+# So we can do the same and don't worry, be happy.
+
+cat <<EOF > ${DST_FILE}
+# Automatically generated by gen-timezones.sh
+
+TZ_UTC       = 0x01
+TZ_RFC       = 0x02
+TZ_MILITARY  = 0x04
+TZ_AMBIGUOUS = 0x08
+TZ_NYI       = 0x10
+TZ_OLSON     = 0x20
+TZ_ALIAS     = 0x40
+TZ_DST       = 0x80
+
+indexToTimezone = {
+EOF
+
+grep ZONE_ABBREV ${SRC_FILE} | sed "s/ZONE_ABBREV( *//g" | sed "s/[),]//g" \
+	| awk '{printf("\t%s : %s,\n", $1, $3)}' >> ${DST_FILE}
+grep ZONE_UNIQUE ${SRC_FILE} | sed "s/ZONE_UNIQUE( *//g" | sed "s/[),]//g" \
+	| awk '{printf("\t%s : %s,\n", $1, $2)}' >> ${DST_FILE}
+
+cat <<EOF >> ${DST_FILE}
+}
+
+timezoneToIndex = {
+EOF
+
+grep ZONE_ABBREV ${SRC_FILE} | sed "s/ZONE_ABBREV( *//g" | sed "s/[),]//g" \
+	| awk '{printf("\t%s : %s,\n", $3, $1)}' >> ${DST_FILE}
+grep ZONE_UNIQUE ${SRC_FILE} | sed "s/ZONE_UNIQUE( *//g" | sed "s/[),]//g" \
+	| awk '{printf("\t%s : %s,\n", $2, $1)}' >> ${DST_FILE}
+grep ZONE_ALIAS  ${SRC_FILE} | sed "s/ZONE_ALIAS( *//g"  | sed "s/[),]//g" \
+	| awk '{printf("\t%s : %s,\n", $2, $1)}' >> ${DST_FILE}
+
+cat <<EOF >> ${DST_FILE}
+}
+
+timezoneAbbrevInfo = {
+EOF
+
+grep ZONE_ABBREV ${SRC_FILE} | sed "s/ZONE_ABBREV( *//g" | sed "s/[),]//g" \
+	| awk '{printf("\t%s : {\"offset\" : %d, \"category\" : %s},\n", $3, $2, $4)}' >> ${DST_FILE}
+echo "}" >> ${DST_FILE}
+
+rm timezones.h
+
+python validate_timezones.py