non-triggered dynamically scheduled units are not allowed to unschedule fixed_time scheduled units

SAS/TMSS/backend/services/scheduling/lib/dynamic_scheduling.py

@@ -1163,6 +1163,10 @@ def unschededule_blocking_scheduled_units_if_needed_and_possible(candidate_sched
     if candidate_scheduling_unit.priority_queue.value == models.PriorityQueueType.Choices.B.value:
         overlapping_scheduled_scheduling_units = overlapping_scheduled_scheduling_units.exclude(priority_queue__value=models.PriorityQueueType.Choices.A.value)
 
+    # non-triggered dynamically scheduled units are not allowed to unschedule fixed_time scheduled units
+    if candidate_scheduling_unit.is_dynamically_scheduled and not candidate_scheduling_unit.interrupts_telescope:
+        overlapping_scheduled_scheduling_units = overlapping_scheduled_scheduling_units.exclude(scheduling_constraints_doc__scheduler='fixed_time')
+
     if not overlapping_scheduled_scheduling_units.exists():
         logger.debug('no scheduled scheduling_units are blocking candidate scheduling_unit id=%s name=%s, nothing needs to be unscheduled', candidate_scheduling_unit.id, candidate_scheduling_unit.name)
         return

SAS/TMSS/backend/src/tmss/tmssapp/models/specification.py

@@ -1368,6 +1368,20 @@ class SchedulingUnitBlueprint(ProjectPropertyMixin, TemplateSchemaMixin, Schedul
         '''
         return self.draft.scheduling_set.project
 
+    @property
+    def is_dynamically_scheduled(self) -> bool:
+        '''is this unit scheduled dynamically?'''
+        if self.scheduling_constraints_doc is not None:
+            return self.scheduling_constraints_doc.get('scheduler', '') == 'dynamic'
+        return False
+
+    @property
+    def is_fixed_time_scheduled(self) -> bool:
+        '''is this unit scheduled at fixed time?'''
+        if self.scheduling_constraints_doc is not None:
+            return self.scheduling_constraints_doc.get('scheduler', '') == 'fixed_time'
+        return False
+
     @property
     def main_observation_used_stations(self) -> list:
         '''return the list of used stations of the main observation task'''