Add typed parse helpers for datetime, date, time and duration

Author: ChrisJr404

docs/docs/parsing.md

@@ -112,3 +112,36 @@ When passing only time information the date will default to today.
     >>> pendulum.parse('12:04:23', exact=True)
     Time(12, 04, 23)
     ```
+
+## Typed helpers
+
+Because `parse()` can return a `DateTime`, `Date`, `Time` or `Duration` depending on the
+input, its return type is a union, which is awkward in type-checked code. If you know which
+type you expect, you can use one of the typed helpers instead. Each one returns that single
+type and raises a `ParserError` if the string represents something else.
+
+```python
+>>> import pendulum
+
+>>> pendulum.parse_datetime('2012-05-03T12:04:23')
+DateTime(2012, 5, 3, 12, 4, 23, tzinfo=Timezone('UTC'))
+
+>>> pendulum.parse_datetime('P2Y3M4DT5H6M7S')
+Traceback (most recent call last):
+...
+ParserError: Text 'P2Y3M4DT5H6M7S' does not represent a datetime, got Duration
+```
+
+`parse_date()` and `parse_time()` expect the string to represent that exact type, so pass
+`exact=True` as you would to `parse()`:
+
+```python
+>>> pendulum.parse_date('2012-05-03', exact=True)
+Date(2012, 5, 3)
+
+>>> pendulum.parse_time('12:04:23', exact=True)
+Time(12, 4, 23)
+
+>>> pendulum.parse_duration('P2Y3M4DT5H6M7S')
+Duration(years=2, months=3, days=4, hours=5, minutes=6, seconds=7)
+```

src/pendulum/__init__.py

@@ -31,6 +31,10 @@
 from pendulum.helpers import week_starts_at
 from pendulum.interval import Interval
 from pendulum.parser import parse as parse
+from pendulum.parser import parse_date as parse_date
+from pendulum.parser import parse_datetime as parse_datetime
+from pendulum.parser import parse_duration as parse_duration
+from pendulum.parser import parse_time as parse_time
 from pendulum.time import Time
 from pendulum.tz import UTC
 from pendulum.tz import fixed_timezone
@@ -423,6 +427,10 @@ def __getattr__(name: str) -> Any:
     "naive",
     "now",
     "parse",
+    "parse_date",
+    "parse_datetime",
+    "parse_duration",
+    "parse_time",
     "set_local_timezone",
     "set_locale",
     "test_local_timezone",

src/pendulum/parser.py

@@ -9,6 +9,7 @@
 from pendulum.duration import Duration
 from pendulum.parsing import _Interval
 from pendulum.parsing import parse as base_parse
+from pendulum.parsing.exceptions import ParserError
 from pendulum.tz.timezone import UTC
 
 
@@ -36,6 +37,68 @@ def parse(text: str, **options: t.Any) -> Date | Time | DateTime | Duration:
     return _parse(text, **options)
 
 
+def parse_datetime(text: str, **options: t.Any) -> DateTime:
+    """Parse a string and return a ``DateTime``.
+
+    Accepts the same options as ``parse()`` but raises a ``ParserError`` if the
+    string represents something else (a date, a time, a duration, ...).
+    """
+    parsed = parse(text, **options)
+    if not isinstance(parsed, pendulum.DateTime):
+        raise _wrong_type(text, "a datetime", parsed)
+
+    return parsed
+
+
+def parse_date(text: str, **options: t.Any) -> Date:
+    """Parse a string and return a ``Date``.
+
+    Accepts the same options as ``parse()`` but raises a ``ParserError`` if the
+    string represents something else. Note that ``parse()`` yields a ``DateTime``
+    for a date string unless ``exact=True`` is passed.
+    """
+    parsed = parse(text, **options)
+    # DateTime is a subclass of Date, so a datetime must not pass as a date.
+    if not isinstance(parsed, pendulum.Date) or isinstance(parsed, pendulum.DateTime):
+        raise _wrong_type(text, "a date", parsed)
+
+    return parsed
+
+
+def parse_time(text: str, **options: t.Any) -> Time:
+    """Parse a string and return a ``Time``.
+
+    Accepts the same options as ``parse()`` but raises a ``ParserError`` if the
+    string represents something else. Note that ``parse()`` yields a ``DateTime``
+    for a time string unless ``exact=True`` is passed.
+    """
+    parsed = parse(text, **options)
+    if not isinstance(parsed, pendulum.Time):
+        raise _wrong_type(text, "a time", parsed)
+
+    return parsed
+
+
+def parse_duration(text: str, **options: t.Any) -> Duration:
+    """Parse a string and return a ``Duration``.
+
+    Accepts the same options as ``parse()`` but raises a ``ParserError`` if the
+    string represents something else.
+    """
+    parsed = parse(text, **options)
+    # Interval is a subclass of Duration, so an interval must not pass as one.
+    if not isinstance(parsed, Duration) or isinstance(parsed, pendulum.Interval):
+        raise _wrong_type(text, "a duration", parsed)
+
+    return parsed
+
+
+def _wrong_type(text: str, expected: str, parsed: object) -> ParserError:
+    return ParserError(
+        f"Text '{text}' does not represent {expected}, got {type(parsed).__name__}"
+    )
+
+
 def _parse(
     text: str, **options: t.Any
 ) -> Date | DateTime | Time | Duration | Interval[DateTime]:

tests/test_parsing.py

@@ -1,7 +1,10 @@
 from __future__ import annotations
 
+import pytest
+
 import pendulum
 
+from pendulum.parsing.exceptions import ParserError
 from tests.conftest import assert_date
 from tests.conftest import assert_datetime
 from tests.conftest import assert_duration
@@ -147,3 +150,74 @@ def test_parse_with_utc_timezone() -> None:
     dt = pendulum.parse("2020-02-05T20:05:37.364951Z")
 
     assert dt.to_iso8601_string() == "2020-02-05T20:05:37.364951Z"
+
+
+def test_parse_datetime() -> None:
+    dt = pendulum.parse_datetime("2016-10-16T12:34:56.123456+01:30")
+
+    assert isinstance(dt, pendulum.DateTime)
+    assert_datetime(dt, 2016, 10, 16, 12, 34, 56, 123456)
+    assert dt.offset == 5400
+
+    # A date string still parses to a DateTime by default.
+    dt = pendulum.parse_datetime("2016-10-16")
+
+    assert isinstance(dt, pendulum.DateTime)
+    assert_datetime(dt, 2016, 10, 16, 0, 0, 0, 0)
+
+    # Options are forwarded to parse().
+    dt = pendulum.parse_datetime("2016-10-16T12:34:56", tz="Europe/Paris")
+
+    assert dt.tz is not None
+    assert dt.tz.name == "Europe/Paris"
+
+
+def test_parse_datetime_raises_for_other_types() -> None:
+    with pytest.raises(ParserError):
+        pendulum.parse_datetime("P2Y3M4DT5H6M7S")
+
+    with pytest.raises(ParserError):
+        pendulum.parse_datetime("2016-10-16", exact=True)
+
+
+def test_parse_date() -> None:
+    d = pendulum.parse_date("2016-10-16", exact=True)
+
+    assert isinstance(d, pendulum.Date)
+    assert_date(d, 2016, 10, 16)
+
+
+def test_parse_date_raises_for_other_types() -> None:
+    # A datetime must not pass as a date, even though DateTime subclasses Date.
+    with pytest.raises(ParserError):
+        pendulum.parse_date("2016-10-16")
+
+    with pytest.raises(ParserError):
+        pendulum.parse_date("12:34:56", exact=True)
+
+
+def test_parse_time() -> None:
+    t = pendulum.parse_time("12:34:56.123456", exact=True)
+
+    assert isinstance(t, pendulum.Time)
+    assert_time(t, 12, 34, 56, 123456)
+
+
+def test_parse_time_raises_for_other_types() -> None:
+    with pytest.raises(ParserError):
+        pendulum.parse_time("2016-10-16", exact=True)
+
+
+def test_parse_duration_helper() -> None:
+    duration = pendulum.parse_duration("P2Y3M4DT5H6M7S")
+
+    assert isinstance(duration, pendulum.Duration)
+    assert_duration(duration, 2, 3, 0, 4, 5, 6, 7)
+
+
+def test_parse_duration_raises_for_other_types() -> None:
+    with pytest.raises(ParserError):
+        pendulum.parse_duration("2016-10-16")
+
+    with pytest.raises(ParserError):
+        pendulum.parse_duration("2008-05-11T15:30:00Z/2008-05-11T16:30:00Z")