refactor: add typing to & do maintenance of periods

CHANGELOG.md

@@ -1,5 +1,38 @@
 # Changelog
 
+# 42.0.0 [#1223](https://github.com/openfisca/openfisca-core/pull/1223)
+
+#### Breaking changes
+
+- Changes to `eternity` instants and periods
+  - Eternity instants are now `<Instant(-1, -1, -1)>` instead of
+    `<Instant(inf, inf, inf)>`
+  - Eternity periods are now `<Period(('eternity', <Instant(-1, -1, -1)>, -1))>`
+    instead of `<Period(('eternity', <Instant(inf, inf, inf)>, inf))>`
+  - The reason is to avoid mixing data types: `inf` is a float, periods and
+    instants are integers. Mixed data types make memory optimisations impossible.
+  - Migration should be straightforward. If you have a test that checks for
+    `inf`, you should update it to check for `-1` or use the `is_eternal` method.
+- `periods.instant` no longer returns `None`
+  - Now, it raises `periods.InstantError`
+
+#### New features
+
+- Introduce `Instant.eternity()`
+  - This behaviour was duplicated across
+  - Now it is encapsulated in a single method
+- Introduce `Instant.is_eternal` and `Period.is_eternal`
+    - These methods check if the instant or period are eternity (`bool`).
+- Now `periods.instant` parses also ISO calendar strings (weeks)
+  - For instance, `2022-W01` is now a valid input
+
+#### Technical changes
+
+- Update `pendulum`
+- Reduce code complexity
+- Remove run-time type-checks
+- Add typing to the periods module
+
 ### 41.5.7 [#1225](https://github.com/openfisca/openfisca-core/pull/1225)
 
 #### Technical changes

openfisca_core/commons/misc.py

@@ -30,10 +30,12 @@ def empty_clone(original: object) -> object:
 
     """
 
+    def __init__(_: object) -> None: ...
+
     Dummy = type(
         "Dummy",
         (original.__class__,),
-        {"__init__": lambda _: None},
+        {"__init__": __init__},
     )
 
     new = Dummy()
@@ -69,6 +71,7 @@ def stringify_array(array: None | t.Array[numpy.generic]) -> str:
         "[<class 'list'>, {}, <function stringify_array...]"
 
     """
+
     if array is None:
         return "None"
 

openfisca_core/periods/__init__.py

@@ -21,26 +21,59 @@
 #
 # See: https://www.python.org/dev/peps/pep-0008/#imports
 
-from .config import (  # noqa: F401
-    DAY,
-    ETERNITY,
+from . import types
+from ._errors import InstantError, ParserError, PeriodError
+from .config import (
     INSTANT_PATTERN,
-    MONTH,
-    WEEK,
-    WEEKDAY,
-    YEAR,
     date_by_instant_cache,
     str_by_instant_cache,
     year_or_month_or_day_re,
 )
-from .date_unit import DateUnit  # noqa: F401
-from .helpers import (  # noqa: F401
+from .date_unit import DateUnit
+from .helpers import (
     instant,
     instant_date,
     key_period_size,
     period,
     unit_weight,
     unit_weights,
 )
-from .instant_ import Instant  # noqa: F401
-from .period_ import Period  # noqa: F401
+from .instant_ import Instant
+from .period_ import Period
+
+WEEKDAY = DateUnit.WEEKDAY
+WEEK = DateUnit.WEEK
+DAY = DateUnit.DAY
+MONTH = DateUnit.MONTH
+YEAR = DateUnit.YEAR
+ETERNITY = DateUnit.ETERNITY
+ISOFORMAT = DateUnit.isoformat
+ISOCALENDAR = DateUnit.isocalendar
+
+__all__ = [
+    "DAY",
+    "DateUnit",
+    "ETERNITY",
+    "INSTANT_PATTERN",
+    "ISOCALENDAR",
+    "ISOFORMAT",
+    "Instant",
+    "InstantError",
+    "MONTH",
+    "ParserError",
+    "Period",
+    "PeriodError",
+    "WEEK",
+    "WEEKDAY",
+    "YEAR",
+    "date_by_instant_cache",
+    "instant",
+    "instant_date",
+    "key_period_size",
+    "period",
+    "str_by_instant_cache",
+    "types",
+    "unit_weight",
+    "unit_weights",
+    "year_or_month_or_day_re",
+]

openfisca_core/periods/_errors.py

@@ -0,0 +1,28 @@
+from pendulum.parsing.exceptions import ParserError
+
+
+class InstantError(ValueError):
+    """Raised when an invalid instant-like is provided."""
+
+    def __init__(self, value: str) -> None:
+        msg = (
+            f"'{value}' is not a valid instant string. Instants are described "
+            "using either the 'YYYY-MM-DD' format, for instance '2015-06-15', "
+            "or the 'YYYY-Www-D' format, for instance '2015-W24-1'."
+        )
+        super().__init__(msg)
+
+
+class PeriodError(ValueError):
+    """Raised when an invalid period-like is provided."""
+
+    def __init__(self, value: str) -> None:
+        msg = (
+            "Expected a period (eg. '2017', 'month:2017-01', 'week:2017-W01-1:3', "
+            f"...); got: '{value}'. Learn more about legal period formats in "
+            "OpenFisca: <https://openfisca.org/doc/coding-the-legislation/35_periods.html#periods-in-simulations>."
+        )
+        super().__init__(msg)
+
+
+__all__ = ["InstantError", "ParserError", "PeriodError"]

openfisca_core/periods/_parsers.py

@@ -1,62 +1,92 @@
-from typing import Optional
+"""To parse periods and instants from strings."""
 
-import re
+from __future__ import annotations
+
+import datetime
 
 import pendulum
-from pendulum.datetime import Date
-from pendulum.parsing import ParserError
 
+from . import types as t
+from ._errors import InstantError, ParserError, PeriodError
 from .date_unit import DateUnit
 from .instant_ import Instant
 from .period_ import Period
 
-invalid_week = re.compile(r".*(W[1-9]|W[1-9]-[0-9]|W[0-5][0-9]-0)$")
 
+def parse_instant(value: str) -> t.Instant:
+    """Parse a string into an instant.
+
+    Args:
+        value (str): The string to parse.
+
+    Returns:
+        An InstantStr.
+
+    Raises:
+        InstantError: When the string is not a valid ISO Calendar/Format.
+        ParserError: When the string couldn't be parsed.
+
+    Examples:
+        >>> parse_instant("2022")
+        Instant((2022, 1, 1))
+
+        >>> parse_instant("2022-02")
+        Instant((2022, 2, 1))
+
+        >>> parse_instant("2022-W02-7")
+        Instant((2022, 1, 16))
 
-def _parse_period(value: str) -> Optional[Period]:
+        >>> parse_instant("2022-W013")
+        Traceback (most recent call last):
+        openfisca_core.periods._errors.InstantError: '2022-W013' is not a va...
+
+        >>> parse_instant("2022-02-29")
+        Traceback (most recent call last):
+        pendulum.parsing.exceptions.ParserError: Unable to parse string [202...
+
+    """
+
+    if not isinstance(value, t.InstantStr):
+        raise InstantError(str(value))
+
+    date = pendulum.parse(value, exact=True)
+
+    if not isinstance(date, datetime.date):
+        msg = f"Unable to parse string [{value}]"
+        raise ParserError(msg)
+
+    return Instant((date.year, date.month, date.day))
+
+
+def parse_period(value: str) -> t.Period:
     """Parses ISO format/calendar periods.
 
     Such as "2012" or "2015-03".
 
     Examples:
-        >>> _parse_period("2022")
+        >>> parse_period("2022")
         Period((<DateUnit.YEAR: 'year'>, Instant((2022, 1, 1)), 1))
 
-        >>> _parse_period("2022-02")
+        >>> parse_period("2022-02")
         Period((<DateUnit.MONTH: 'month'>, Instant((2022, 2, 1)), 1))
 
-        >>> _parse_period("2022-W02-7")
+        >>> parse_period("2022-W02-7")
         Period((<DateUnit.WEEKDAY: 'weekday'>, Instant((2022, 1, 16)), 1))
 
     """
-    # If it's a complex period, next!
-    if len(value.split(":")) != 1:
-        return None
 
-    # Check for a non-empty string.
-    if not (value and isinstance(value, str)):
-        raise AttributeError
+    try:
+        instant = parse_instant(value)
 
-    # If it's negative, next!
-    if value[0] == "-":
-        raise ValueError
+    except InstantError as error:
+        raise PeriodError(value) from error
 
-    # If it's an invalid week, next!
-    if invalid_week.match(value):
-        raise ParserError
-
-    unit = _parse_unit(value)
-    date = pendulum.parse(value, exact=True)
-
-    if not isinstance(date, Date):
-        raise ValueError
-
-    instant = Instant((date.year, date.month, date.day))
+    unit = parse_unit(value)
 
     return Period((unit, instant, 1))
 
 
-def _parse_unit(value: str) -> DateUnit:
+def parse_unit(value: str) -> t.DateUnit:
     """Determine the date unit of a date string.
 
     Args:
@@ -66,32 +96,26 @@ def _parse_unit(value: str) -> DateUnit:
         A DateUnit.
 
     Raises:
-        ValueError when no DateUnit can be determined.
+        InstantError: when no DateUnit can be determined.
 
     Examples:
-        >>> _parse_unit("2022")
+        >>> parse_unit("2022")
         <DateUnit.YEAR: 'year'>
 
-        >>> _parse_unit("2022-W03-01")
+        >>> parse_unit("2022-W03-1")
         <DateUnit.WEEKDAY: 'weekday'>
 
     """
-    length = len(value.split("-"))
-    isweek = value.find("W") != -1
 
-    if length == 1:
-        return DateUnit.YEAR
+    if not isinstance(value, t.InstantStr):
+        raise InstantError(str(value))
 
-    if length == 2:
-        if isweek:
-            return DateUnit.WEEK
+    length = len(value.split("-"))
 
-        return DateUnit.MONTH
+    if isinstance(value, t.ISOCalendarStr):
+        return DateUnit.isocalendar[-length]
 
-    if length == 3:
-        if isweek:
-            return DateUnit.WEEKDAY
+    return DateUnit.isoformat[-length]
 
-        return DateUnit.DAY
 
-    raise ValueError
+__all__ = ["parse_instant", "parse_period", "parse_unit"]

openfisca_core/periods/config.py

@@ -1,22 +1,20 @@
 import re
 
-from .date_unit import DateUnit
+import pendulum
 
-WEEKDAY = DateUnit.WEEKDAY
-WEEK = DateUnit.WEEK
-DAY = DateUnit.DAY
-MONTH = DateUnit.MONTH
-YEAR = DateUnit.YEAR
-ETERNITY = DateUnit.ETERNITY
+from . import types as t
 
 # Matches "2015", "2015-01", "2015-01-01"
 # Does not match "2015-13", "2015-12-32"
 INSTANT_PATTERN = re.compile(
     r"^\d{4}(-(0[1-9]|1[012]))?(-(0[1-9]|1[012])-(0[1-9]|[12][0-9]|3[01]))?$",
 )
 
-date_by_instant_cache: dict = {}
-str_by_instant_cache: dict = {}
+date_by_instant_cache: dict[t.Instant, pendulum.Date] = {}
+str_by_instant_cache: dict[t.Instant, t.InstantStr] = {}
 year_or_month_or_day_re = re.compile(
     r"(18|19|20)\d{2}(-(0?[1-9]|1[0-2])(-([0-2]?\d|3[0-1]))?)?$",
 )
+
+
+__all__ = ["INSTANT_PATTERN", "date_by_instant_cache", "str_by_instant_cache"]