Added helper for migrations involving AleaIdField to populate fields from ObjectMapping table.

dddp/migrations/__init__.py

@@ -1,4 +1,7 @@
+import functools
+from django.db import migrations
 from django.db.migrations.operations.base import Operation
+from dddp.models import AleaIdField, get_meteor_id
 
 
 class TruncateOperation(Operation):
@@ -35,3 +38,48 @@ class TruncateOperation(Operation):
     def describe(self):
         """Describe what the operation does in console output."""
         return "Truncate tables"
+
+
+def set_default_forwards(app_name, operation, apps, schema_editor):
+    """Set default value for AleaIdField."""
+    model = apps.get_model(app_name, operation.model_name)
+    for obj_pk in model.objects.values_list('pk', flat=True):
+        model.objects.filter(pk=obj_pk).update(**{
+            operation.name: get_meteor_id(model, obj_pk),
+        })
+
+
+def set_default_reverse(app_name, operation, apps, schema_editor):
+    """Unset default value for AleaIdField."""
+    model = apps.get_model(app_name, operation.model_name)
+    for obj_pk in model.objects.values_list('pk', flat=True):
+        get_meteor_id(model, obj_pk)
+
+
+class DefaultAleaIdOperations(object):
+
+    def __init__(self, app_name):
+        self.app_name = app_name
+
+    def __add__(self, operations):
+        default_operations = []
+        for operation in operations:
+            if not isinstance(operation, migrations.AlterField):
+                continue
+            if not isinstance(operation.field, AleaIdField):
+                continue
+            if operation.name != 'aid':
+                continue
+            if operation.field.null:
+                continue
+            default_operations.append(
+                migrations.RunPython(
+                    code=functools.partial(
+                        set_default_forwards, self.app_name, operation,
+                    ),
+                    reverse_code=functools.partial(
+                        set_default_reverse, self.app_name, operation,
+                    ),
+                )
+            )
+        return default_operations + operations