ranges: Start module.

The ledger report wants to use this functionality, so make it available in a
higher-level module.

I took the opportunity to clean up a lot of the surrounding type
declarations. It is less flexible, since it relies on the static list of
types in RangeT, but I don't think the other method actually worked at all
except by cheating with generic Any.

conservancy_beancount/plugin/core.py

@@ -21,6 +21,7 @@ import re
 from .. import config as configmod
 from .. import data
 from .. import errors as errormod
+from .. import ranges
 
 from typing import (
     Any,
@@ -49,10 +50,10 @@ from ..beancount_types import (
 
 # I expect these will become configurable in the future, which is why I'm
 # keeping them outside of a class, but for now constants will do.
-DEFAULT_START_DATE: datetime.date = datetime.date(2020, 3, 1)
+DEFAULT_START_DATE = datetime.date(2020, 3, 1)
 # The default stop date leaves a little room after so it's easy to test
 # dates past the far end of the range.
-DEFAULT_STOP_DATE: datetime.date = datetime.date(datetime.MAXYEAR, 1, 1)
+DEFAULT_STOP_DATE = datetime.date(datetime.MAXYEAR, 1, 1)
 
 ### TYPE DEFINITIONS
 
@@ -74,38 +75,6 @@ class Hook(Generic[Entry], metaclass=abc.ABCMeta):
 
 ### HELPER CLASSES
 
-class LessComparable(metaclass=abc.ABCMeta):
-    @abc.abstractmethod
-    def __le__(self, other: Any) -> bool: ...
-
-    @abc.abstractmethod
-    def __lt__(self, other: Any) -> bool: ...
-
-
-CT = TypeVar('CT', bound=LessComparable)
-class _GenericRange(Generic[CT]):
-    """Convenience class to check whether a value is within a range.
-
-    `foo in generic_range` is equivalent to `start <= foo < stop`.
-    Since we have multiple user-configurable ranges, having the check
-    encapsulated in an object helps implement the check consistently, and
-    makes it easier for subclasses to override.
-    """
-
-    def __init__(self, start: CT, stop: CT) -> None:
-        self.start = start
-        self.stop = stop
-
-    def __repr__(self) -> str:
-        return "{clsname}({self.start!r}, {self.stop!r})".format(
-            clsname=type(self).__name__,
-            self=self,
-        )
-
-    def __contains__(self, item: CT) -> bool:
-        return self.start <= item < self.stop
-
-
 class MetadataEnum:
     """Map acceptable metadata values to their normalized forms.
 
@@ -178,7 +147,7 @@ class MetadataEnum:
 class TransactionHook(Hook[Transaction]):
     DIRECTIVE = Transaction
     SKIP_FLAGS: Container[str] = frozenset()
-    TXN_DATE_RANGE: _GenericRange = _GenericRange(DEFAULT_START_DATE, DEFAULT_STOP_DATE)
+    TXN_DATE_RANGE = ranges.DateRange(DEFAULT_START_DATE, DEFAULT_STOP_DATE)
 
     def _run_on_txn(self, txn: Transaction) -> bool:
         """Check whether we should run on a given transaction

conservancy_beancount/ranges.py

@@ -0,0 +1,59 @@
+"""ranges.py - Higher-typed range classes"""
+# Copyright © 2020  Brett Smith
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+import datetime
+
+from decimal import Decimal
+
+from typing import (
+    Generic,
+    TypeVar,
+    Union,
+)
+
+RangeT = TypeVar(
+    'RangeT',
+    # This is a relatively arbitrary set of types. Feel free to add to it if
+    # you need; the types just need to support enough comparisons to implement
+    # _GenericRange.__contains__.
+    datetime.date,
+    datetime.datetime,
+    datetime.time,
+    Union[int, Decimal],
+)
+
+class _GenericRange(Generic[RangeT]):
+    """range for higher-level types
+
+    This class knows how to check membership for higher-level types just like
+    Python's built-in range. It does not know how to iterate or step.
+    """
+    def __init__(self, start: RangeT, stop: RangeT) -> None:
+        self.start: RangeT = start
+        self.stop: RangeT = stop
+
+    def __repr__(self) -> str:
+        return "{clsname}({self.start!r}, {self.stop!r})".format(
+            clsname=type(self).__name__,
+            self=self,
+        )
+
+    def __contains__(self, item: RangeT) -> bool:
+        return self.start <= item < self.stop
+
+
+DateRange = _GenericRange[datetime.date]
+DecimalCompatRange = _GenericRange[Union[int, Decimal]]

tests/test_ranges.py

@@ -0,0 +1,64 @@
+"""test_ranges.py - Unit tests for range classes"""
+# Copyright © 2020  Brett Smith
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+import datetime
+
+import pytest
+
+from conservancy_beancount import ranges
+
+ONE_DAY = datetime.timedelta(days=1)
+
+@pytest.mark.parametrize('start,stop', [
+    # One month
+    (datetime.date(2018, 3, 1), datetime.date(2018, 4, 1)),
+    # Three months
+    (datetime.date(2018, 6, 1), datetime.date(2018, 9, 1)),
+    # Six months, spanning year
+    (datetime.date(2018, 9, 1), datetime.date(2019, 3, 1)),
+    # Nine months
+    (datetime.date(2018, 2, 1), datetime.date(2018, 12, 1)),
+    # Twelve months on Jan 1
+    (datetime.date(2018, 1, 1), datetime.date(2019, 1, 1)),
+    # Twelve months spanning year
+    (datetime.date(2018, 3, 1), datetime.date(2019, 3, 1)),
+    # Eighteen months spanning year
+    (datetime.date(2018, 3, 1), datetime.date(2019, 9, 1)),
+    # Wild
+    (datetime.date(2018, 1, 1), datetime.date(2020, 4, 15)),
+])
+def test_date_range(start, stop):
+    date_range = ranges.DateRange(start, stop)
+    assert (start - ONE_DAY) not in date_range
+    assert start in date_range
+    assert (start + ONE_DAY) in date_range
+    assert (stop - ONE_DAY) in date_range
+    assert stop not in date_range
+    assert (stop + ONE_DAY) not in date_range
+
+def test_date_range_one_day():
+    start = datetime.date(2018, 7, 1)
+    date_range = ranges.DateRange(start, start + ONE_DAY)
+    assert (start - ONE_DAY) not in date_range
+    assert start in date_range
+    assert (start + ONE_DAY) not in date_range
+
+def test_date_range_empty():
+    date = datetime.date(2018, 8, 10)
+    date_range = ranges.DateRange(date, date)
+    assert (date - ONE_DAY) not in date_range
+    assert date not in date_range
+    assert (date + ONE_DAY) not in date_range