Creation Receipt

dynamic_initial_data/base.py

@@ -1,11 +1,13 @@
+import json
+
 from django.apps import apps
 from django.contrib.contenttypes.models import ContentType
 from django.db.transaction import atomic
 from django.utils import timezone
 from django.utils.module_loading import import_string
 
 from dynamic_initial_data.exceptions import InitialDataCircularDependency, InitialDataMissingApp
-from dynamic_initial_data.models import RegisteredForDeletionReceipt
+from dynamic_initial_data.models import RegisteredForDeletionReceipt, CreationReceipt
 
 
 class BaseInitialData(object):
@@ -33,6 +35,32 @@ def register_for_deletion(self, *model_objs):
         """
         self.model_objs_registered_for_deletion.extend(model_objs)
 
+    @atomic
+    def create_once(self, model_class, unique_name, **kwargs):
+        """
+        Ensures that a model with given attributes is only created once. This is ideal for fixture data we want
+        initially populated within Ambition that can be permanently deleted by customer.
+
+        1. First we check for Creation Receipt.
+        2. If one didn't previously exist then create Model w/ Attributes.
+        """
+
+        # Get the Content Type
+        content_type = ContentType.objects.get_for_model(model_class)
+
+        # See if receipt exists for given model and attributes, if not then create
+        receipt, created = CreationReceipt.objects.get_or_create(
+            unique_name=unique_name,
+            defaults={
+                'model_class_type': content_type,
+                'model_attributes': json.dumps(kwargs)
+            }
+        )
+
+        # If receipt did not previously exist then go ahead and create model with given attributes
+        if created:
+            model_class.objects.create(**kwargs)
+
     def update_initial_data(self, *args, **kwargs):
         """
         Raises an error if the subclass does not implement this

dynamic_initial_data/migrations/0002_creationreceipt.py

@@ -0,0 +1,24 @@
+# Generated by Django 2.2.8 on 2020-02-19 20:16
+
+import django.contrib.postgres.fields.jsonb
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('contenttypes', '0002_remove_content_type_name'),
+        ('dynamic_initial_data', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='CreationReceipt',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('model_attributes', django.contrib.postgres.fields.jsonb.JSONField()),
+                ('model_class_type', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='contenttypes.ContentType')),
+            ],
+        ),
+    ]

dynamic_initial_data/models.py

@@ -1,5 +1,6 @@
 from django.contrib.contenttypes.fields import GenericForeignKey
 from django.contrib.contenttypes.models import ContentType
+from django.contrib.postgres.fields import JSONField
 from django.db import models
 from manager_utils import ManagerUtilsManager
 
@@ -22,3 +23,9 @@ class RegisteredForDeletionReceipt(models.Model):
 
     class Meta:
         unique_together = ('model_obj_type', 'model_obj_id')
+
+
+class CreationReceipt(models.Model):
+    name = models.CharField(max_length=256, unique=True)
+    model_class_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
+    model_attributes = JSONField()

setup.py

@@ -42,7 +42,7 @@ def get_version():
     ],
     license='MIT',
     install_requires=[
-        'Django>=2.0',
+        'Django>=2.0,<3.0',
         'django-manager-utils>=1.4.0',
     ],
     tests_require=[