WIP: workaround for content types, but not so much for auth

django_migration_fixture/__init__.py

@@ -1,12 +1,24 @@
 import os
+
 from django.core import serializers
+from django.core.management.color import no_style
+from django.db import connection
+from django.db.models import signals
 
 
 class FixtureObjectDoesNotExist(Exception):
     """Raised when attempting to roll back a fixture and the instance can't be found"""
     pass
 
 
+def reset_db_sequences(models):
+    if not models:
+        return
+    with connection.cursor() as cursor:
+        for sql in connection.ops.sequence_reset_sql(no_style(), models):
+            cursor.execute(sql)
+
+
 def fixture(app, fixtures, fixtures_dir='fixtures', raise_does_not_exist=False):
     """
     Load fixtures using a data migration.
@@ -35,9 +47,32 @@ def get_objects():
                 for obj in objects:
                     yield obj
 
-    def load_fixture(apps, schema_editor):
-        for obj in get_objects():
-            obj.save()
+    def load_fixture(app_config, schema_editor):
+        """Entrypoint for RunPython to load the fixture.
+
+        This delays the actual loading until this app itself is being called
+        through the post_migrate signal hook.  This is necessary for
+        the contenttypes and auth data to be available.
+
+        After the fixture has been loaded the database sequences for affected
+        models are being 'reset' (using `coalesce` with PostgreSQL)."""
+
+        def signal_handler(app_config, sender, **kwargs):
+            if sender.label == "django_migration_fixture":
+                assert app_config.label == "django_migration_fixture"
+
+                models = set()
+                for obj in get_objects():
+                    obj.save()
+                    models.add(obj.object._meta.model)
+
+                reset_db_sequences(models)
+
+                # Disconnect the signal, otherwise we might be called during
+                # e.g. flush (in tests) again.
+                signals.post_migrate.disconnect(signal_handler, weak=False)
+
+        signals.post_migrate.connect(signal_handler, weak=False)
 
     def unload_fixture(apps, schema_editor):
         for obj in get_objects():
@@ -55,4 +90,4 @@ def unload_fixture(apps, schema_editor):
                 if not raise_does_not_exist:
                     raise FixtureObjectDoesNotExist("Model %s instance with kwargs %s does not exist." % (model, kwargs))
 
-    return dict(code=load_fixture, reverse_code=unload_fixture)
+    return dict(code=load_fixture, reverse_code=unload_fixture)

django_migration_fixture/migrations/__init__.py

@@ -0,0 +1,2 @@
+# Empty fake migration module to make Django consider us for the `post_migrate`
+# signal.

django_migration_fixture/models.py

@@ -0,0 +1 @@
+# Make Django consider us for the `post_migrate` signal.