[FIX] resource: allow to plan 0 hours

The method `plan_hours` does nothing if the `hours` parameter is equal to 0.
This commit adds the 0 case in the logic, and add an optional `resource` in the
parameters.

Example: A workorder works each days between 8am and 4pm. If we call
`plan_hours(0)` at 9pm, we want to get 8am the next day. Currently, it
sends back 9pm.

Before this commit, a hack existed consisting to send a very small value to
`plan_hours`. The holidays and non-working time were taken into account and the
result was rounded to the second.  We can now send explicitely 0 and the
non-working hours will be skipped.

addons/resource/models/resource.py

@@ -295,7 +295,7 @@ class ResourceCalendar(models.Model):
         )
 
     @api.multi
-    def plan_hours(self, hours, day_dt, compute_leaves=False, domain=None):
+    def plan_hours(self, hours, day_dt, compute_leaves=False, domain=None, resource=None):
         """
         `compute_leaves` controls whether or not this method is taking into
         account the global leaves.
@@ -309,11 +309,11 @@ class ResourceCalendar(models.Model):
 
         # which method to use for retrieving intervals
         if compute_leaves:
-            get_intervals = partial(self._work_intervals, domain=domain)
+            get_intervals = partial(self._work_intervals, domain=domain, resource=resource)
         else:
             get_intervals = self._attendance_intervals
 
-        if hours > 0:
+        if hours >= 0:
             delta = timedelta(days=14)
             for n in range(100):
                 dt = day_dt + delta * n
@@ -323,8 +323,7 @@ class ResourceCalendar(models.Model):
                         return revert(start + timedelta(hours=hours))
                     hours -= interval_hours
             return False
-
-        elif hours < 0:
+        else:
             hours = abs(hours)
             delta = timedelta(days=14)
             for n in range(100):
@@ -336,9 +335,6 @@ class ResourceCalendar(models.Model):
                     hours -= interval_hours
             return False
 
-        else:
-            return revert(day_dt)
-
     @api.multi
     def plan_days(self, days, day_dt, compute_leaves=False, domain=None):
         """

addons/resource/tests/test_resource.py

@@ -260,9 +260,11 @@ class TestCalendar(TestResourceCommon):
         time = self.calendar_jean.plan_hours(-10, datetime_tz(2018, 4, 10, 0, 0, 0, tzinfo=self.jean.tz), compute_leaves=True)
         self.assertEqual(time, datetime_tz(2018, 4, 6, 14, 0, 0, tzinfo=self.jean.tz))
 
-        # zero planning
-        time = self.calendar_jean.plan_hours(0, datetime_tz(2018, 4, 10, 0, 0, 0, tzinfo=self.jean.tz), compute_leaves=True)
-        self.assertEqual(time, datetime_tz(2018, 4, 10, 0, 0, 0, tzinfo=self.jean.tz))
+        # zero planning with holidays
+        time = self.calendar_jean.plan_hours(0, datetime_tz(2018, 4, 11, 0, 0, 0, tzinfo=self.jean.tz), compute_leaves=True)
+        self.assertEqual(time, datetime_tz(2018, 4, 12, 8, 0, 0, tzinfo=self.jean.tz))
+        time = self.calendar_jean.plan_hours(0, datetime_tz(2018, 4, 10, 0, 0, 0, tzinfo=self.jean.tz), compute_leaves=False)
+        self.assertEqual(time, datetime_tz(2018, 4, 10, 8, 0, 0, tzinfo=self.jean.tz))
 
         # very small planning
         time = self.calendar_jean.plan_hours(0.0002, datetime_tz(2018, 4, 10, 0, 0, 0, tzinfo=self.jean.tz), compute_leaves=True)