[FIX] project: recurring dates of monthly repeated task until date

Computing the recurrences of a task repeating every X months until a
certain date generates too much dates

Steps to reproduce:
1. Install Project
2. Go to Settings > Project > Tasks Management and enable Recurring
   Tasks
3. Open any project in the Project app and create a new task then edit
   it
4. Enable the Recurrent field of the task
5. In the Recurrence tab, edit:
   - Repeat Every: 6 Months
   - Until: End Date: one year from now
6. The recurrence message says there are 11 tasks but there should only
   be 2

Solution:
Generate the recurrences until the `repeat_until` date is reached if the
`repeat_type` is 'until', otherwise generate as much recurrences as the
count
Also relax the constraint on the `repeat_day` and `repeat_until` to not
raise an error if `repeat_until` is the last day of the month

Problem:
The recurrence of a task with `repeat_unit` month and `repeat_interval`
different than 1 with a `repeat_type` until creates too much tasks,
exceeding the `repeat_until`

opw-3076593

closes odoo/odoo#106596

Signed-off-by: Laurent Stukkens (ltu) <ltu@odoo.com>

addons/project/models/project_task_recurrence.py

@@ -8,8 +8,6 @@ from calendar import monthrange
 from dateutil.relativedelta import relativedelta
 from dateutil.rrule import rrule, rruleset, DAILY, WEEKLY, MONTHLY, YEARLY, MO, TU, WE, TH, FR, SA, SU
 
-import math
-
 MONTHS = {
     'january': 31,
     'february': 28,
@@ -140,8 +138,9 @@ class ProjectTaskRecurrence(models.Model):
 
     @api.constrains('repeat_unit', 'repeat_on_month', 'repeat_day', 'repeat_type', 'repeat_until')
     def _check_repeat_until_month(self):
-        if self.filtered(lambda r: r.repeat_type == 'until' and r.repeat_unit == 'month' and r.repeat_until and r.repeat_on_month == 'date' and int(r.repeat_day) > r.repeat_until.day):
-            raise ValidationError('The end date should be after the day of the month')
+        if self.filtered(lambda r: r.repeat_type == 'until' and r.repeat_unit == 'month' and r.repeat_until and r.repeat_on_month == 'date'
+           and int(r.repeat_day) > r.repeat_until.day and monthrange(r.repeat_until.year, r.repeat_until.month)[1] != r.repeat_until.day):
+            raise ValidationError('The end date should be after the day of the month or the last day of the month')
 
     @api.model
     def _get_recurring_fields(self):
@@ -179,16 +178,16 @@ class ProjectTaskRecurrence(models.Model):
             rrule_kwargs['freq'] = MONTHLY
             if repeat_on_month == 'date':
                 start = date_start - relativedelta(days=1)
-                if repeat_type == 'until' and repeat_until > date_start:
-                    delta = relativedelta(repeat_until, date_start)
-                    count = math.floor((delta.years * 12 + delta.months) / repeat_interval)
-                for i in range(count):
+                start = start.replace(day=min(repeat_day, monthrange(start.year, start.month)[1]))
+                if start < date_start:
+                    # Ensure the next recurrence is in the future
+                    start += relativedelta(months=repeat_interval)
                     start = start.replace(day=min(repeat_day, monthrange(start.year, start.month)[1]))
-                    if i == 0 and start < date_start:
-                        # Ensure the next recurrence is in the future
-                        start += relativedelta(months=repeat_interval)
+                can_generate_date = (lambda: start <= repeat_until) if repeat_type == 'until' else (lambda: len(dates) < count)
+                while can_generate_date():
                     dates.append(start)
                     start += relativedelta(months=repeat_interval)
+                    start = start.replace(day=min(repeat_day, monthrange(start.year, start.month)[1]))
                 return dates
         elif repeat_unit == 'year':
             rrule_kwargs['freq'] = YEARLY

addons/project/tests/test_project_recurrence.py

@@ -455,6 +455,69 @@ class TestProjectrecurrence(SavepointCase):
         self.assertEqual(dates[0], datetime(2020, 7, 3))
         self.assertEqual(dates[1], datetime(2021, 1, 3))
 
+        # Should generate a date at the last day of the current month
+        dates = self.env['project.task.recurrence']._get_next_recurring_dates(
+            date_start=date(2022, 2, 26),
+            repeat_interval=1,
+            repeat_unit='month',
+            repeat_type='until',
+            repeat_until=date(2022, 2, 28),
+            repeat_on_month='date',
+            repeat_on_year=False,
+            weekdays=False,
+            repeat_day=31,
+            repeat_week=False,
+            repeat_month=False,
+            count=5)
+
+        self.assertEqual(len(dates), 1)
+        self.assertEqual(dates[0], date(2022, 2, 28))
+
+        dates = self.env['project.task.recurrence']._get_next_recurring_dates(
+            date_start=date(2022, 11, 26),
+            repeat_interval=3,
+            repeat_unit='month',
+            repeat_type='until',
+            repeat_until=date(2024, 2, 29),
+            repeat_on_month='date',
+            repeat_on_year=False,
+            weekdays=False,
+            repeat_day=25,
+            repeat_week=False,
+            repeat_month=False,
+            count=5)
+
+        self.assertEqual(len(dates), 5)
+        self.assertEqual(dates[0], date(2023, 2, 25))
+        self.assertEqual(dates[1], date(2023, 5, 25))
+        self.assertEqual(dates[2], date(2023, 8, 25))
+        self.assertEqual(dates[3], date(2023, 11, 25))
+        self.assertEqual(dates[4], date(2024, 2, 25))
+
+        # Use the exact same parameters than the previous test but with a repeat_day that is not passed yet
+        # So we generate an additional date in the current month
+        dates = self.env['project.task.recurrence']._get_next_recurring_dates(
+            date_start=date(2022, 11, 26),
+            repeat_interval=3,
+            repeat_unit='month',
+            repeat_type='until',
+            repeat_until=date(2024, 2, 29),
+            repeat_on_month='date',
+            repeat_on_year=False,
+            weekdays=False,
+            repeat_day=31,
+            repeat_week=False,
+            repeat_month=False,
+            count=5)
+
+        self.assertEqual(len(dates), 6)
+        self.assertEqual(dates[0], date(2022, 11, 30))
+        self.assertEqual(dates[1], date(2023, 2, 28))
+        self.assertEqual(dates[2], date(2023, 5, 31))
+        self.assertEqual(dates[3], date(2023, 8, 31))
+        self.assertEqual(dates[4], date(2023, 11, 30))
+        self.assertEqual(dates[5], date(2024, 2, 29))
+
     def test_recurrence_next_dates_year(self):
         dates = self.env['project.task.recurrence']._get_next_recurring_dates(
             date_start=date(2020, 12, 1),