Add precondition counting

django_goals/admin.py

@@ -62,7 +62,10 @@ def has_delete_permission(self, request, obj=None):
 @admin.register(Goal)
 class GoalAdmin(DjangoObjectActions, admin.ModelAdmin):
     list_display = (
-        'id', 'state', 'handler', 'precondition_date', 'created_at',
+        'id', 'state', 'handler',
+        'precondition_date',
+        'waiting_for_count',
+        'created_at',
         'progress_count',
     )
     list_filter = ('state', 'precondition_date')
@@ -74,6 +77,7 @@ class GoalAdmin(DjangoObjectActions, admin.ModelAdmin):
         'handler',
         'instructions_pre',
         'precondition_date',
+        'waiting_for_count',
         'deadline',
         'created_at',
         'related_objects',

django_goals/migrations/0004_goal_waiting_for_count.py

@@ -0,0 +1,18 @@
+# Generated by Django 5.1.3 on 2024-12-08 00:41
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('django_goals', '0003_remove_goal_goals_waiting_for_worker_idx_and_more'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='goal',
+            name='waiting_for_count',
+            field=models.IntegerField(default=0, help_text='Number of precondition goals we are still waiting for.'),
+        ),
+    ]

django_goals/models.py

@@ -62,6 +62,10 @@ class Goal(models.Model):
         through='GoalDependency',
         blank=True,
     )
+    waiting_for_count = models.IntegerField(
+        default=0,
+        help_text=_('Number of precondition goals we are still waiting for.'),
+    )
     deadline = models.DateTimeField(
         default=timezone.now,
         help_text=_('Goals having deadline sooner will be pursued first.'),
@@ -381,6 +385,14 @@ def handle_waiting_for_worker():
 
     time_taken = time.monotonic() - start_time
 
+    # decrease waiting-for counter in dependent goals
+    if goal.state == GoalState.ACHIEVED:
+        Goal.objects.filter(
+            precondition_goals=goal,
+        ).update(
+            waiting_for_count=models.F('waiting_for_count') - 1,
+        )
+
     progress = goal.progress.create(
         success=success,
         created_at=now,
@@ -539,7 +551,24 @@ def schedule(
 
 
 def add_precondition_goals(goal, precondition_goals):
-    goal.precondition_goals.add(*precondition_goals)
+    if not precondition_goals:
+        return
+    # get a list of new preconditions, and make sure nobody is working on them
+    new_precondition_goals = list(Goal.objects.filter(
+        id__in=[g.id for g in precondition_goals],
+    ).exclude(
+        dependent_goals=goal,
+    ).select_for_update(no_key=True))
+    if not new_precondition_goals:
+        return
+    # add to our preconditions
+    goal.precondition_goals.add(*new_precondition_goals)
+    # update waiting-for counter
+    for precondition_goal in new_precondition_goals:
+        if precondition_goal.state != GoalState.ACHIEVED:
+            goal.waiting_for_count += 1
+    goal.save(update_fields=['waiting_for_count'])
+    # move deadline earlier for preconditions, if needed
     update_goals_deadline(goal.precondition_goals.all(), goal.deadline)
 
 

django_goals/models_tests.py

@@ -53,10 +53,12 @@ def test_handle_waiting_for_worker_guarded_updates_dependent_goals(goal):
     next_goal = GoalFactory(
         state=GoalState.WAITING_FOR_PRECONDITIONS,
         precondition_goals=[goal],
+        waiting_for_count=1,
     )
     handle_waiting_for_worker_guarded()
     next_goal.refresh_from_db()
     assert next_goal.state == GoalState.WAITING_FOR_WORKER
+    assert next_goal.waiting_for_count == 0
 
 
 @pytest.mark.django_db
@@ -71,3 +73,17 @@ def test_schedule_updates_deadline():
     )
     goal_a.refresh_from_db()
     assert goal_a.deadline == now - datetime.timedelta(minutes=1)
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize(
+    ('goal', 'expected_waiting_for'),
+    [
+        ({'state': GoalState.WAITING_FOR_WORKER}, 1),
+        ({'state': GoalState.ACHIEVED}, 0),
+    ],
+    indirect=['goal'],
+)
+def test_schedule_updates_waiting_for_count(goal, expected_waiting_for):
+    next_goal = schedule(noop, precondition_goals=[goal])
+    assert next_goal.waiting_for_count == expected_waiting_for