Improve todo timespan handling

ical/todo.py

@@ -29,7 +29,7 @@
     Uri,
     RelatedTo,
 )
-from .util import dtstamp_factory, normalize_datetime, uid_factory
+from .util import dtstamp_factory, normalize_datetime, uid_factory, local_timezone
 
 
 class TodoStatus(str, enum.Enum):
@@ -213,16 +213,28 @@ def computed_duration(self) -> datetime.timedelta | None:
     @property
     def timespan(self) -> Timespan:
         """Return a timespan representing the item start and due date."""
-        if not self.start:
-            raise ValueError("Event must have a start and due date to calculate timespan")
-        return Timespan.of(self.start, self.due or self.start)
+        return self.timespan_of(local_timezone())
 
     def timespan_of(self, tzinfo: datetime.tzinfo) -> Timespan:
         """Return a timespan representing the item start and due date."""
-        if not self.start:
-            raise ValueError("Event must have a start and due date to calculate timespan")
+        dtstart = self.dtstart
+        dtend = self.due
+        if dtstart is None:
+            if dtend is None:
+                # A component with the DTSTART and DUE specifies a to-do that
+                # will be associated with each successive calendar date, until
+                # it is completed.
+                dtstart = datetime.datetime.now(tzinfo).date()
+                dtend = dtstart + datetime.timedelta(days=1)
+            else:
+                # Component with a DTSTART but no DUE date will be sorted next
+                # to the due date.
+                dtstart = dtend
+        elif dtend is None:
+            # Component with a DTSTART but not DUE date will be sorted next to the start date
+            dtend = dtstart
         return Timespan.of(
-            normalize_datetime(self.start, tzinfo), normalize_datetime(self.due or self.start, tzinfo)
+            normalize_datetime(dtstart, tzinfo), normalize_datetime(dtend, tzinfo)
         )
 
     @property

tests/test_calendar_stream.py

@@ -11,12 +11,14 @@
 
 from ical.exceptions import CalendarParseError
 from ical.calendar_stream import CalendarStream, IcsCalendarStream
+from ical.store import EventStore, TodoStore
 
 MAX_ITERATIONS = 30
 TESTDATA_PATH = pathlib.Path("tests/testdata/")
 TESTDATA_FILES = list(TESTDATA_PATH.glob("*.ics"))
 TESTDATA_IDS = [ x.stem for x in TESTDATA_FILES ]
 
+
 def test_empty_ics(mock_prodid: Generator[None, None, None]) -> None:
     """Test serialization of an empty ics file."""
     calendar = IcsCalendarStream.calendar_from_ics("")
@@ -72,7 +74,7 @@ def test_serialize(filename: pathlib.Path, snapshot: SnapshotAssertion) -> None:
 
 
 @pytest.mark.parametrize("filename", TESTDATA_FILES, ids=TESTDATA_IDS)
-def test_iteration(filename: pathlib.Path, snapshot: SnapshotAssertion) -> None:
+def test_timeline_iteration(filename: pathlib.Path) -> None:
     """Fixture to ensure all calendar events are valid and support iteration."""
     with filename.open() as f:
         cal = IcsCalendarStream.from_ics(f.read())
@@ -83,6 +85,18 @@ def test_iteration(filename: pathlib.Path, snapshot: SnapshotAssertion) -> None:
             assert event is not None
 
 
+@pytest.mark.parametrize("filename", TESTDATA_FILES, ids=TESTDATA_IDS)
+def test_todo_list_iteration(filename: pathlib.Path) -> None:
+    """Fixture to read golden file and compare to golden output."""
+    cal = CalendarStream.from_ics(filename.read_text())
+    if not cal.calendars:
+        return
+    calendar = cal.calendars[0]
+    tl = TodoStore(calendar).todo_list()
+    for todo in itertools.islice(tl, MAX_ITERATIONS):
+        assert todo is not None
+
+
 def test_invalid_ics() -> None:
     """Test parsing failures for ics content."""
     with pytest.raises(CalendarParseError, match="Failed to parse calendar stream"):

tests/test_todo.py

@@ -7,6 +7,7 @@
 from typing import Any
 from unittest.mock import patch
 
+from freezegun import freeze_time
 import pytest
 
 from ical.exceptions import CalendarParseError
@@ -103,3 +104,50 @@ def test_is_recurring() -> None:
         datetime.date(2024, 2, 3),
         datetime.date(2024, 2, 4),
     ]
+
+
+def test_timestamp_start_due() -> None:
+    """Test a timespan of a Todo with a start and due date."""
+    todo = Todo(
+        summary="Example",
+        dtstart=datetime.date(2022, 8, 1),
+        due=datetime.date(2022, 8, 7),
+    )
+
+    with patch("ical.todo.local_timezone", return_value=zoneinfo.ZoneInfo("CET")):
+        ts = todo.timespan
+    assert ts.start.isoformat() == "2022-08-01T00:00:00+02:00"
+    assert ts.end.isoformat() == "2022-08-07T00:00:00+02:00"
+
+    ts = todo.timespan_of(zoneinfo.ZoneInfo("America/Regina"))
+    assert ts.start.isoformat() == "2022-08-01T00:00:00-06:00"
+    assert ts.end.isoformat() == "2022-08-07T00:00:00-06:00"
+
+
+def test_timespan_missing_dtstart() -> None:
+    """Test a timespan of a Todo without a dtstart."""
+    todo = Todo(summary="Example", due=datetime.date(2022, 8, 7))
+
+    with patch("ical.todo.local_timezone", return_value=zoneinfo.ZoneInfo("Pacific/Honolulu")):
+        ts = todo.timespan
+    assert ts.start.isoformat() == "2022-08-07T00:00:00-10:00"
+    assert ts.end.isoformat() == "2022-08-07T00:00:00-10:00"
+
+    ts = todo.timespan_of(zoneinfo.ZoneInfo("America/Regina"))
+    assert ts.start.isoformat() == "2022-08-07T00:00:00-06:00"
+    assert ts.end.isoformat() == "2022-08-07T00:00:00-06:00"
+
+
+def test_timespan_fallback() -> None:
+    """Test a timespan of a Todo with no explicit dtstart and due date"""
+
+    with freeze_time("2022-09-03T09:38:05", tz_offset=10), patch("ical.todo.local_timezone", return_value=zoneinfo.ZoneInfo("Pacific/Honolulu")):
+        todo = Todo(summary="Example")
+        ts = todo.timespan
+    assert ts.start.isoformat() == "2022-09-03T00:00:00-10:00"
+    assert ts.end.isoformat() == "2022-09-04T00:00:00-10:00"
+
+    with freeze_time("2022-09-03T09:38:05", tz_offset=10), patch("ical.todo.local_timezone", return_value=zoneinfo.ZoneInfo("Pacific/Honolulu")):
+        ts = todo.timespan_of(zoneinfo.ZoneInfo("America/Regina"))
+    assert ts.start.isoformat() == "2022-09-03T00:00:00-06:00"
+    assert ts.end.isoformat() == "2022-09-04T00:00:00-06:00"