Handle correctly timestamps with fractions of minute in the timezone offset

Close #1272.

5 files changed, 154 insertions, 81 deletions

diff --git a/NEWS b/NEWS
index 5967927..b3e1464 100644
--- a/NEWS
+++ b/NEWS
@@ -6,6 +6,8 @@ What's new in psycopg 2.9
 
 - ``with connection`` starts a transaction on autocommit transactions too
   (:ticket:`#941`).
+- Timezones with fractional minutes are supported on Python 3.7 and following
+  (:ticket:`#1272`).
 - Escape table and column names in `~cursor.copy_from()` and
   `~cursor.copy_to()`.
 - Connection exceptions with sqlstate ``08XXX`` reclassified as
diff --git a/doc/src/usage.rst b/doc/src/usage.rst
index 3aafa90..335e750 100644
--- a/doc/src/usage.rst
+++ b/doc/src/usage.rst
@@ -580,25 +580,33 @@ The PostgreSQL type :sql:`timestamp with time zone` (a.k.a.
 a `~datetime.datetime.tzinfo` attribute set to a
 `~psycopg2.tz.FixedOffsetTimezone` instance.
 
-    >>> cur.execute("SET TIME ZONE 'Europe/Rome';")  # UTC + 1 hour
-    >>> cur.execute("SELECT '2010-01-01 10:30:45'::timestamptz;")
+    >>> cur.execute("SET TIME ZONE 'Europe/Rome'")  # UTC + 1 hour
+    >>> cur.execute("SELECT '2010-01-01 10:30:45'::timestamptz")
     >>> cur.fetchone()[0].tzinfo
     psycopg2.tz.FixedOffsetTimezone(offset=60, name=None)
 
-Note that only time zones with an integer number of minutes are supported:
-this is a limitation of the Python `datetime` module.  A few historical time
-zones had seconds in the UTC offset: these time zones will have the offset
-rounded to the nearest minute, with an error of up to 30 seconds.
+.. note::
 
-    >>> cur.execute("SET TIME ZONE 'Asia/Calcutta';")  # offset was +5:53:20
-    >>> cur.execute("SELECT '1930-01-01 10:30:45'::timestamptz;")
-    >>> cur.fetchone()[0].tzinfo
-    psycopg2.tz.FixedOffsetTimezone(offset=353, name=None)
+    Before Python 3.7, the `datetime` module only supported timezones with an
+    integer number of minutes. A few historical time zones had seconds in the
+    UTC offset: these time zones will have the offset rounded to the nearest
+    minute, with an error of up to 30 seconds, on Python versions before 3.7.
+
+        >>> cur.execute("SET TIME ZONE 'Asia/Calcutta'")  # offset was +5:21:10
+        >>> cur.execute("SELECT '1900-01-01 10:30:45'::timestamptz")
+        >>> cur.fetchone()[0].tzinfo
+        # On Python 3.6: 5h, 21m
+        psycopg2.tz.FixedOffsetTimezone(offset=datetime.timedelta(0, 19260), name=None)
+        # On Python 3.7 and following: 5h, 21m, 10s
+        psycopg2.tz.FixedOffsetTimezone(offset=datetime.timedelta(seconds=19270), name=None)
 
 .. versionchanged:: 2.2.2
     timezones with seconds are supported (with rounding). Previously such
     timezones raised an error.
 
+.. versionchanged:: 2.9
+    timezones with seconds are supported without rounding.
+
 
 .. index::
     double: Date objects; Infinite
diff --git a/lib/tz.py b/lib/tz.py
index 81cd8f8..357aac0 100644
--- a/lib/tz.py
+++ b/lib/tz.py
@@ -45,6 +45,11 @@ class FixedOffsetTimezone(datetime.tzinfo):
     offset and name that instance will be returned. This saves memory and
     improves comparability.
 
+    .. versionchanged:: 2.9
+
+        The constructor can take either a timedelta or a number of minutes of
+        offset. Previously only minutes were supported.
+
     .. __: https://docs.python.org/library/datetime.html
     """
     _name = None
@@ -54,7 +59,9 @@ class FixedOffsetTimezone(datetime.tzinfo):
 
     def __init__(self, offset=None, name=None):
         if offset is not None:
-            self._offset = datetime.timedelta(minutes=offset)
+            if not isinstance(offset, datetime.timedelta):
+                offset = datetime.timedelta(minutes=offset)
+            self._offset = offset
         if name is not None:
             self._name = name
 
@@ -70,13 +77,23 @@ class FixedOffsetTimezone(datetime.tzinfo):
             return tz
 
     def __repr__(self):
-        offset_mins = self._offset.seconds // 60 + self._offset.days * 24 * 60
         return "psycopg2.tz.FixedOffsetTimezone(offset=%r, name=%r)" \
-            % (offset_mins, self._name)
+            % (self._offset, self._name)
+
+    def __eq__(self, other):
+        if isinstance(other, FixedOffsetTimezone):
+            return self._offset == other._offset
+        else:
+            return NotImplemented
+
+    def __ne__(self, other):
+        if isinstance(other, FixedOffsetTimezone):
+            return self._offset != other._offset
+        else:
+            return NotImplemented
 
     def __getinitargs__(self):
-        offset_mins = self._offset.seconds // 60 + self._offset.days * 24 * 60
-        return offset_mins, self._name
+        return self._offset, self._name
 
     def utcoffset(self, dt):
         return self._offset
@@ -84,14 +101,16 @@ class FixedOffsetTimezone(datetime.tzinfo):
     def tzname(self, dt):
         if self._name is not None:
             return self._name
-        else:
-            seconds = self._offset.seconds + self._offset.days * 86400
-            hours, seconds = divmod(seconds, 3600)
-            minutes = seconds / 60
-            if minutes:
-                return "%+03d:%d" % (hours, minutes)
-            else:
-                return "%+03d" % hours
+
+        minutes, seconds = divmod(self._offset.total_seconds(), 60)
+        hours, minutes = divmod(minutes, 60)
+        rv = "%+03d" % hours
+        if minutes or seconds:
+            rv += ":%02d" % minutes
+            if seconds:
+                rv += ":%02d" % seconds
+
+        return rv
 
     def dst(self, dt):
         return ZERO
diff --git a/psycopg/typecast_datetime.c b/psycopg/typecast_datetime.c
index 095fce1..d700069 100644
--- a/psycopg/typecast_datetime.c
+++ b/psycopg/typecast_datetime.c
@@ -129,10 +129,11 @@ static PyObject *
 _parse_noninftz(const char *str, Py_ssize_t len, PyObject *curs)
 {
     PyObject* rv = NULL;
+    PyObject *tzoff = NULL;
     PyObject *tzinfo = NULL;
     PyObject *tzinfo_factory;
     int n, y=0, m=0, d=0;
-    int hh=0, mm=0, ss=0, us=0, tz=0;
+    int hh=0, mm=0, ss=0, us=0, tzsec=0;
     const char *tp = NULL;
 
     Dprintf("typecast_PYDATETIMETZ_cast: s = %s", str);
@@ -147,11 +148,11 @@ _parse_noninftz(const char *str, Py_ssize_t len, PyObject *curs)
     }
 
     if (len > 0) {
-        n = typecast_parse_time(tp, NULL, &len, &hh, &mm, &ss, &us, &tz);
+        n = typecast_parse_time(tp, NULL, &len, &hh, &mm, &ss, &us, &tzsec);
         Dprintf("typecast_PYDATETIMETZ_cast: n = %d,"
             " len = " FORMAT_CODE_PY_SSIZE_T ","
-            " hh = %d, mm = %d, ss = %d, us = %d, tz = %d",
-            n, len, hh, mm, ss, us, tz);
+            " hh = %d, mm = %d, ss = %d, us = %d, tzsec = %d",
+            n, len, hh, mm, ss, us, tzsec);
         if (n < 3 || n > 6) {
             PyErr_SetString(DataError, "unable to parse time");
             goto exit;
@@ -169,17 +170,20 @@ _parse_noninftz(const char *str, Py_ssize_t len, PyObject *curs)
     if (n >= 5 && tzinfo_factory != Py_None) {
         /* we have a time zone, calculate minutes and create
            appropriate tzinfo object calling the factory */
-        Dprintf("typecast_PYDATETIMETZ_cast: UTC offset = %ds", tz);
-
-        /* The datetime module requires that time zone offsets be
-           a whole number of minutes, so truncate the seconds to the
-           closest minute. */
-        // printf("%d %d %d\n", tz, tzmin, round(tz / 60.0));
-        if (!(tzinfo = PyObject_CallFunction(tzinfo_factory, "i",
-                (int)round(tz / 60.0)))) {
+        Dprintf("typecast_PYDATETIMETZ_cast: UTC offset = %ds", tzsec);
+
+#if PY_VERSION_HEX < 0x03070000
+        /* Before Python 3.7 the timezone offset had to be a whole number
+         * of minutes, so round the seconds to the closest minute */
+        tzsec = 60 * (int)round(tzsec / 60.0);
+#endif
+        if (!(tzoff = PyDelta_FromDSU(0, tzsec, 0))) { goto exit; }
+        if (!(tzinfo = PyObject_CallFunctionObjArgs(
+                tzinfo_factory, tzoff, NULL))) {
             goto exit;
         }
-    } else {
+    }
+    else {
         Py_INCREF(Py_None);
         tzinfo = Py_None;
     }
@@ -192,6 +196,7 @@ _parse_noninftz(const char *str, Py_ssize_t len, PyObject *curs)
         y, m, d, hh, mm, ss, us, tzinfo);
 
 exit:
+    Py_XDECREF(tzoff);
     Py_XDECREF(tzinfo);
     return rv;
 }
@@ -232,17 +237,18 @@ typecast_PYDATETIMETZ_cast(const char *str, Py_ssize_t len, PyObject *curs)
 static PyObject *
 typecast_PYTIME_cast(const char *str, Py_ssize_t len, PyObject *curs)
 {
-    PyObject* obj = NULL;
+    PyObject* rv = NULL;
+    PyObject *tzoff = NULL;
     PyObject *tzinfo = NULL;
     PyObject *tzinfo_factory;
-    int n, hh=0, mm=0, ss=0, us=0, tz=0;
+    int n, hh=0, mm=0, ss=0, us=0, tzsec=0;
 
     if (str == NULL) { Py_RETURN_NONE; }
 
-    n = typecast_parse_time(str, NULL, &len, &hh, &mm, &ss, &us, &tz);
+    n = typecast_parse_time(str, NULL, &len, &hh, &mm, &ss, &us, &tzsec);
     Dprintf("typecast_PYTIME_cast: n = %d, len = " FORMAT_CODE_PY_SSIZE_T ", "
-            "hh = %d, mm = %d, ss = %d, us = %d, tz = %d",
-            n, len, hh, mm, ss, us, tz);
+            "hh = %d, mm = %d, ss = %d, us = %d, tzsec = %d",
+            n, len, hh, mm, ss, us, tzsec);
 
     if (n < 3 || n > 6) {
         PyErr_SetString(DataError, "unable to parse time");
@@ -254,25 +260,32 @@ typecast_PYTIME_cast(const char *str, Py_ssize_t len, PyObject *curs)
     }
     tzinfo_factory = ((cursorObject *)curs)->tzinfo_factory;
     if (n >= 5 && tzinfo_factory != Py_None) {
-        /* we have a time zone, calculate minutes and create
+        /* we have a time zone, calculate seconds and create
            appropriate tzinfo object calling the factory */
-        Dprintf("typecast_PYTIME_cast: UTC offset = %ds", tz);
-
-        /* The datetime module requires that time zone offsets be
-           a whole number of minutes, so truncate the seconds to the
-           closest minute. */
-        tzinfo = PyObject_CallFunction(tzinfo_factory, "i",
-            (int)round(tz / 60.0));
-    } else {
+        Dprintf("typecast_PYTIME_cast: UTC offset = %ds", tzsec);
+
+#if PY_VERSION_HEX < 0x03070000
+        /* Before Python 3.7 the timezone offset had to be a whole number
+         * of minutes, so round the seconds to the closest minute */
+        tzsec = 60 * (int)round(tzsec / 60.0);
+#endif
+        if (!(tzoff = PyDelta_FromDSU(0, tzsec, 0))) { goto exit; }
+        if (!(tzinfo = PyObject_CallFunctionObjArgs(tzinfo_factory, tzoff, NULL))) {
+            goto exit;
+        }
+    }
+    else {
         Py_INCREF(Py_None);
         tzinfo = Py_None;
     }
-    if (tzinfo != NULL) {
-        obj = PyObject_CallFunction((PyObject*)PyDateTimeAPI->TimeType, "iiiiO",
-                                    hh, mm, ss, us, tzinfo);
-        Py_DECREF(tzinfo);
-    }
-    return obj;
+
+    rv = PyObject_CallFunction((PyObject*)PyDateTimeAPI->TimeType, "iiiiO",
+                                hh, mm, ss, us, tzinfo);
+
+exit:
+    Py_XDECREF(tzoff);
+    Py_XDECREF(tzinfo);
+    return rv;
 }
 
 
diff --git a/tests/test_dates.py b/tests/test_dates.py
index 29c37b0..4ba1455 100755
--- a/tests/test_dates.py
+++ b/tests/test_dates.py
@@ -23,6 +23,7 @@
 # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
 # License for more details.
 
+import sys
 import math
 import pickle
 from datetime import date, datetime, time, timedelta
@@ -157,17 +158,27 @@ class DatetimeTests(ConnectingTestCase, CommonDatetimeTestsMixin):
         self.check_time_tz("-01", -3600)
         self.check_time_tz("+01:15", 4500)
         self.check_time_tz("-01:15", -4500)
-        # The Python datetime module does not support time zone
-        # offsets that are not a whole number of minutes.
-        # We round the offset to the nearest minute.
-        self.check_time_tz("+01:15:00", 60 * (60 + 15))
-        self.check_time_tz("+01:15:29", 60 * (60 + 15))
-        self.check_time_tz("+01:15:30", 60 * (60 + 16))
-        self.check_time_tz("+01:15:59", 60 * (60 + 16))
-        self.check_time_tz("-01:15:00", -60 * (60 + 15))
-        self.check_time_tz("-01:15:29", -60 * (60 + 15))
-        self.check_time_tz("-01:15:30", -60 * (60 + 16))
-        self.check_time_tz("-01:15:59", -60 * (60 + 16))
+        if sys.version_info < (3, 7):
+            # The Python < 3.7 datetime module does not support time zone
+            # offsets that are not a whole number of minutes.
+            # We round the offset to the nearest minute.
+            self.check_time_tz("+01:15:00", 60 * (60 + 15))
+            self.check_time_tz("+01:15:29", 60 * (60 + 15))
+            self.check_time_tz("+01:15:30", 60 * (60 + 16))
+            self.check_time_tz("+01:15:59", 60 * (60 + 16))
+            self.check_time_tz("-01:15:00", -60 * (60 + 15))
+            self.check_time_tz("-01:15:29", -60 * (60 + 15))
+            self.check_time_tz("-01:15:30", -60 * (60 + 16))
+            self.check_time_tz("-01:15:59", -60 * (60 + 16))
+        else:
+            self.check_time_tz("+01:15:00", 60 * (60 + 15))
+            self.check_time_tz("+01:15:29", 60 * (60 + 15) + 29)
+            self.check_time_tz("+01:15:30", 60 * (60 + 15) + 30)
+            self.check_time_tz("+01:15:59", 60 * (60 + 15) + 59)
+            self.check_time_tz("-01:15:00", -(60 * (60 + 15)))
+            self.check_time_tz("-01:15:29", -(60 * (60 + 15) + 29))
+            self.check_time_tz("-01:15:30", -(60 * (60 + 15) + 30))
+            self.check_time_tz("-01:15:59", -(60 * (60 + 15) + 59))
 
     def check_datetime_tz(self, str_offset, offset):
         base = datetime(2007, 1, 1, 13, 30, 29)
@@ -192,17 +203,27 @@ class DatetimeTests(ConnectingTestCase, CommonDatetimeTestsMixin):
         self.check_datetime_tz("-01", -3600)
         self.check_datetime_tz("+01:15", 4500)
         self.check_datetime_tz("-01:15", -4500)
-        # The Python datetime module does not support time zone
-        # offsets that are not a whole number of minutes.
-        # We round the offset to the nearest minute.
-        self.check_datetime_tz("+01:15:00", 60 * (60 + 15))
-        self.check_datetime_tz("+01:15:29", 60 * (60 + 15))
-        self.check_datetime_tz("+01:15:30", 60 * (60 + 16))
-        self.check_datetime_tz("+01:15:59", 60 * (60 + 16))
-        self.check_datetime_tz("-01:15:00", -60 * (60 + 15))
-        self.check_datetime_tz("-01:15:29", -60 * (60 + 15))
-        self.check_datetime_tz("-01:15:30", -60 * (60 + 16))
-        self.check_datetime_tz("-01:15:59", -60 * (60 + 16))
+        if sys.version_info < (3, 7):
+            # The Python < 3.7 datetime module does not support time zone
+            # offsets that are not a whole number of minutes.
+            # We round the offset to the nearest minute.
+            self.check_datetime_tz("+01:15:00", 60 * (60 + 15))
+            self.check_datetime_tz("+01:15:29", 60 * (60 + 15))
+            self.check_datetime_tz("+01:15:30", 60 * (60 + 16))
+            self.check_datetime_tz("+01:15:59", 60 * (60 + 16))
+            self.check_datetime_tz("-01:15:00", -60 * (60 + 15))
+            self.check_datetime_tz("-01:15:29", -60 * (60 + 15))
+            self.check_datetime_tz("-01:15:30", -60 * (60 + 16))
+            self.check_datetime_tz("-01:15:59", -60 * (60 + 16))
+        else:
+            self.check_datetime_tz("+01:15:00", 60 * (60 + 15))
+            self.check_datetime_tz("+01:15:29", 60 * (60 + 15) + 29)
+            self.check_datetime_tz("+01:15:30", 60 * (60 + 15) + 30)
+            self.check_datetime_tz("+01:15:59", 60 * (60 + 15) + 59)
+            self.check_datetime_tz("-01:15:00", -(60 * (60 + 15)))
+            self.check_datetime_tz("-01:15:29", -(60 * (60 + 15) + 29))
+            self.check_datetime_tz("-01:15:30", -(60 * (60 + 15) + 30))
+            self.check_datetime_tz("-01:15:59", -(60 * (60 + 15) + 59))
 
     def test_parse_time_no_timezone(self):
         self.assertEqual(self.TIME("13:30:29", self.curs).tzinfo, None)
@@ -628,17 +649,27 @@ class FixedOffsetTimezoneTests(unittest.TestCase):
     def test_repr_with_positive_offset(self):
         tzinfo = FixedOffsetTimezone(5 * 60)
         self.assertEqual(repr(tzinfo),
-            "psycopg2.tz.FixedOffsetTimezone(offset=300, name=None)")
+            "psycopg2.tz.FixedOffsetTimezone(offset=%r, name=None)"
+            % timedelta(minutes=5 * 60))
 
     def test_repr_with_negative_offset(self):
         tzinfo = FixedOffsetTimezone(-5 * 60)
         self.assertEqual(repr(tzinfo),
-            "psycopg2.tz.FixedOffsetTimezone(offset=-300, name=None)")
+            "psycopg2.tz.FixedOffsetTimezone(offset=%r, name=None)"
+            % timedelta(minutes=-5 * 60))
+
+    def test_init_with_timedelta(self):
+        td = timedelta(minutes=5 * 60)
+        tzinfo = FixedOffsetTimezone(td)
+        self.assertEqual(tzinfo, FixedOffsetTimezone(5 * 60))
+        self.assertEqual(repr(tzinfo),
+            "psycopg2.tz.FixedOffsetTimezone(offset=%r, name=None)" % td)
 
     def test_repr_with_name(self):
         tzinfo = FixedOffsetTimezone(name="FOO")
         self.assertEqual(repr(tzinfo),
-            "psycopg2.tz.FixedOffsetTimezone(offset=0, name='FOO')")
+            "psycopg2.tz.FixedOffsetTimezone(offset=%r, name='FOO')"
+            % timedelta(0))
 
     def test_instance_caching(self):
         self.assert_(FixedOffsetTimezone(name="FOO")