intervals: use whole intervals

With this the budget over/undershoot will be displayed relative to the
budget assigned for that whole interval, not relative to how far you are
through the interval

src/fava/core/__init__.py

@@ -64,6 +64,7 @@
 from fava.util.date import interval_ends
 from fava.util.typing import BeancountOptions
 
+
 if TYPE_CHECKING:  # pragma: no cover
     from beancount.core.prices import PriceMap
     from beancount.core.realization import RealAccount

src/fava/util/date.py

@@ -102,6 +102,39 @@ def format_date_filter(self, date: datetime.date) -> str:
         return date.strftime("%Y-%m")
 
 
+def get_prev_interval(
+    date: datetime.date, interval: Interval
+) -> datetime.date:
+    """Get the start date of the interval in which the date falls.
+
+    Args:
+        date: A date.
+        intereval: An interval.
+
+    Returns:
+        The start date of the `interval` before `date`.
+
+    """
+    # pylint: disable=too-many-return-statements
+    try:
+        if interval is Interval.YEAR:
+            return datetime.date(date.year, 1, 1)
+        if interval is Interval.QUARTER:
+            for i in [10, 7, 4]:
+                if date.month > i:
+                    return datetime.date(date.year, i, 1)
+            return datetime.date(date.year, 1, 1)
+        if interval is Interval.MONTH:
+            return datetime.date(date.year, date.month, 1)
+        if interval is Interval.WEEK:
+            return date - datetime.timedelta(date.weekday())
+        if interval is Interval.DAY:
+            return date
+    except (ValueError, OverflowError):
+        return datetime.date.max
+    raise NotImplementedError
+
+
 def get_next_interval(
     date: datetime.date, interval: Interval
 ) -> datetime.date:
@@ -151,11 +184,10 @@ def interval_ends(
         Dates corresponding to the starts/ends of intervals between `first` and
         `last`.
     """
+    yield get_prev_interval(first, interval)
     while first < last:
-        yield first
         first = get_next_interval(first, interval)
-
-    yield last
+        yield first
 
 
 def substitute(string: str, fye: FiscalYearEnd | None = None) -> str:

tests/__snapshots__/test_core_charts.py-test_interval_totals

@@ -11,7 +11,7 @@
   "budgets": {
    "EUR": 31.42857142857142857142857145
   },
-  "date": "2012-11-18"
+  "date": "2012-11-01"
  },
  {
   "account_balances": {
@@ -26,7 +26,7 @@
    "EUR": 80.00
   },
   "budgets": {
-   "EUR": 48.57142857142857142857142861
+   "EUR": 88.57142857142857142857142865
   },
   "date": "2012-12-01"
  }

tests/__snapshots__/test_core_charts.py-test_interval_totals-2

@@ -11,7 +11,7 @@
   "budgets": {
    "EUR": 31.42857142857142857142857145
   },
-  "date": "2012-11-18"
+  "date": "2012-11-01"
  },
  {
   "account_balances": {
@@ -26,7 +26,7 @@
    "USD": 40.000
   },
   "budgets": {
-   "EUR": 48.57142857142857142857142861
+   "EUR": 88.57142857142857142857142865
   },
   "date": "2012-12-01"
  }

tests/__snapshots__/test_core_charts.py-test_interval_totals_inverted

@@ -11,7 +11,7 @@
   "budgets": {
    "EUR": -31.42857142857142857142857145
   },
-  "date": "2012-11-18"
+  "date": "2012-11-01"
  },
  {
   "account_balances": {
@@ -26,7 +26,7 @@
    "EUR": -80.00
   },
   "budgets": {
-   "EUR": -48.57142857142857142857142861
+   "EUR": -88.57142857142857142857142865
   },
   "date": "2012-12-01"
  }

tests/__snapshots__/test_core_charts.py-test_interval_totals_inverted-2

@@ -11,7 +11,7 @@
   "budgets": {
    "EUR": -31.42857142857142857142857145
   },
-  "date": "2012-11-18"
+  "date": "2012-11-01"
  },
  {
   "account_balances": {
@@ -26,7 +26,7 @@
    "USD": -40.000
   },
   "budgets": {
-   "EUR": -48.57142857142857142857142861
+   "EUR": -88.57142857142857142857142865
   },
   "date": "2012-12-01"
  }

tests/__snapshots__/test_core_charts.py-test_net_worth

@@ -1426,6 +1426,6 @@
    "USD": 102452.53144,
    "VACHR": -82
   },
-  "date": "2016-05-10"
+  "date": "2016-06-01"
  }
 ]

tests/test_util_date.py

@@ -10,6 +10,7 @@
 from fava.util.date import FiscalYearEnd
 from fava.util.date import get_fiscal_period
 from fava.util.date import get_next_interval
+from fava.util.date import get_prev_interval
 from fava.util.date import Interval
 from fava.util.date import interval_ends
 from fava.util.date import month_offset
@@ -80,14 +81,43 @@ def test_get_next_intervalfail2() -> None:
         get_next_interval(date(2016, 4, 18), "decade")  # type: ignore
 
 
+@pytest.mark.parametrize(
+    "input_date_string,interval,expect",
+    [
+        ("2016-01-01", Interval.DAY, "2016-01-01"),
+        ("2016-01-01", Interval.WEEK, "2015-12-28"),
+        ("2016-01-01", Interval.MONTH, "2016-01-01"),
+        ("2016-01-01", Interval.QUARTER, "2016-01-01"),
+        ("2016-01-01", Interval.YEAR, "2016-01-01"),
+        ("2016-12-31", Interval.DAY, "2016-12-31"),
+        ("2016-12-31", Interval.WEEK, "2016-12-26"),
+        ("2016-12-31", Interval.MONTH, "2016-12-01"),
+        ("2016-12-31", Interval.QUARTER, "2016-10-01"),
+        ("2016-12-31", Interval.YEAR, "2016-01-01"),
+        ("9999-12-31", Interval.QUARTER, "9999-10-01"),
+        ("9999-12-31", Interval.YEAR, "9999-01-01"),
+    ],
+)
+def test_get_prev_interval(
+    input_date_string: str, interval: Interval, expect: str
+) -> None:
+    get = get_prev_interval(_to_date(input_date_string), interval)
+    assert get == _to_date(expect)
+
+
+def test_get_prev_intervalfail2() -> None:
+    with pytest.raises(NotImplementedError):
+        get_prev_interval(date(2016, 4, 18), "decade")  # type: ignore
+
+
 def test_interval_tuples() -> None:
     assert list(
         interval_ends(date(2014, 3, 5), date(2014, 5, 5), Interval.MONTH)
     ) == [
-        date(2014, 3, 5),
+        date(2014, 3, 1),
         date(2014, 4, 1),
         date(2014, 5, 1),
-        date(2014, 5, 5),
+        date(2014, 6, 1),
     ]
     assert list(
         interval_ends(date(2014, 1, 1), date(2014, 5, 1), Interval.MONTH)
@@ -100,7 +130,7 @@ def test_interval_tuples() -> None:
     ]
     assert list(
         interval_ends(date(2014, 3, 5), date(2014, 5, 5), Interval.YEAR)
-    ) == [date(2014, 3, 5), date(2014, 5, 5)]
+    ) == [date(2014, 1, 1), date(2015, 1, 1)]
     assert list(
         interval_ends(date(2014, 1, 1), date(2015, 1, 1), Interval.YEAR)
     ) == [date(2014, 1, 1), date(2015, 1, 1)]