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fix(oauth): parse ISO timestamps with negative UTC offsets #1990

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fix(oauth): parse ISO timestamps with negative UTC offsets #1990

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13 changes: 10 additions & 3 deletions slack_sdk/oauth/installation_store/internals.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,10 +2,17 @@
from typing import Type, TypeVar, Union


def _replace_utc_designator(iso_datetime_str: str) -> str:
if iso_datetime_str.endswith(("Z", "z")):
return iso_datetime_str[:-1] + "+00:00"
return iso_datetime_str


def _from_iso_format_to_datetime(iso_datetime_str: str) -> datetime:
if "+" not in iso_datetime_str:
iso_datetime_str += "+00:00"
return datetime.fromisoformat(iso_datetime_str)
dt = datetime.fromisoformat(_replace_utc_designator(iso_datetime_str))
if dt.tzinfo is None:
dt = dt.replace(tzinfo=timezone.utc)
return dt
Comment on lines 11 to +15

@WilliamBergamin WilliamBergamin Oct 20, 2026

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Swap a trailing Z for +00:00 before parsing so Z works on every supported version of python. Only the last character, not str.replace: RFC 3339 §5.6 only allows Z as the final offset, which is also how CPython's own parser treats it. Lowercase z is allowed by the RFC and already parses on main under CPython, so keeping it avoids a second regression.

Suggested change
def _from_iso_format_to_datetime(iso_datetime_str: str) -> datetime:
if "+" not in iso_datetime_str:
iso_datetime_str += "+00:00"
return datetime.fromisoformat(iso_datetime_str)
dt = datetime.fromisoformat(iso_datetime_str)
if dt.tzinfo is None:
dt = dt.replace(tzinfo=timezone.utc)
return dt
def _replace_utc_designator(iso_datetime_str: str) -> str:
if iso_datetime_str.endswith(("Z", "z")):
return iso_datetime_str[:-1] + "+00:00"
return iso_datetime_str
def _from_iso_format_to_datetime(iso_datetime_str: str) -> datetime:
dt = datetime.fromisoformat(_replace_utc_designator(iso_datetime_str))
if dt.tzinfo is None:
dt = dt.replace(tzinfo=timezone.utc)
return dt



def _from_iso_format_to_unix_timestamp(iso_datetime_str: str) -> float:
Expand Down
13 changes: 13 additions & 0 deletions tests/slack_sdk/oauth/installation_store/test_internals.py
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,17 @@ def test_iso_format(self):
dt = _from_iso_format_to_datetime("2021-07-14 08:00:17")
self.assertEqual(dt.timestamp(), 1626249617.0)

def test_iso_format_with_utc_offset(self):
dt = _from_iso_format_to_datetime("2021-07-14 17:00:17+09:00")
self.assertEqual(dt.timestamp(), 1626249617.0)
dt = _from_iso_format_to_datetime("2021-07-14 03:00:17-05:00")
self.assertEqual(dt.timestamp(), 1626249617.0)

def test_iso_format_with_utc_designator(self):
for iso_datetime_str in ["2021-07-14T08:00:17Z", "2021-07-14T08:00:17z", "2021-07-14T08:00:17.000Z"]:
dt = _from_iso_format_to_datetime(iso_datetime_str)
self.assertEqual(dt.timestamp(), 1626249617.0)


@WilliamBergamin WilliamBergamin Oct 20, 2026

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Could we add coverage for the UTC designator? No test exercises Z right now, which is why the 3.7-3.10 regression doesn't show up in CI.

    def test_iso_format_with_utc_designator(self):
        for iso_datetime_str in ["2021-07-14T08:00:17Z", "2021-07-14T08:00:17z", "2021-07-14T08:00:17.000Z"]:
            dt = _from_iso_format_to_datetime(iso_datetime_str)
            self.assertEqual(dt.timestamp(), 1626249617.0)

and a ("2023-11-28T22:11:19Z", int, 1701209479) case in the test_timestamp_to_type parametrize list.

@pytest.mark.parametrize(
"ts,target_type,expected_result",
Expand All @@ -30,6 +41,8 @@ def test_iso_format(self):
(datetime(2023, 11, 28, 22, 9, 7, tzinfo=timezone.utc), int, 1701209347),
("1701209605", int, 1701209605),
("2023-11-28 22:11:19", int, 1701209479),
("2023-11-28 17:11:19-05:00", int, 1701209479),
("2023-11-28T22:11:19Z", int, 1701209479),
(1701209998.3429494, float, 1701209998.3429494),
(datetime(2023, 11, 28, 22, 20, 25, 262571, tzinfo=timezone.utc), float, 1701210025.262571),
("1701210054.4672053", float, 1701210054.4672053),
Expand Down
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