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# Conflicts:
#	.gitignore

alembic_data/__init__.py

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+"""Alembic-Data is an extension for alembic that creates automatic data migrations.
+
+Data migrations (in contrast to schema migrations) are performed on the contents of database tables. They allow you to
+create, update, and delete rows inside the database. Alembic-Data provides a framework to generate these migrations
+automatically.
+
+Using Alembic-Data is very simple. You can use the `register_object` function to register an object in the database.
+Alembic data will make sure that the next migration creates the registered object. This is normally only useful for
+tables that do not contain any user data (as the migrations would have to be generated depending on the actual data).
+Instead the typical usecase is to combine the `register_object` function with the `@managed_model` decorator to tell
+Alembic-Data that a model will be managed exclusively programmatically.
+
+The `@managed_model` decorator is used on your declarative model classes. For any `@managed_model` Alembic-Data will
+created your `register_object` and will additionally delete any rows from that database that do not belong to any
+registered object.
+"""
+
+from typing import List, Any, Dict
+
+from alembic.autogenerate import comparators
+from alembic.autogenerate.api import AutogenContext
+from alembic.operations.ops import UpgradeOps
+from sqlalchemy.ext.declarative import DeclarativeMeta
+
+from .ops import *
+
+__all__ = ["managed_model", "register_object"]
+
+
+def managed_model(cls: DeclarativeMeta) -> DeclarativeMeta:
+    """Marks this model as a managed model.
+
+    Class decorator to be used on declarative SQLAlchemy models. Using this decorator causes alembic-data to assume that
+    objects for this model will only be created through code and the `register_object` function.
+
+    :param cls: The class to be decorated. Must be a SQLAlchemy declarative class.
+    :return: The decorated class, unchanged.
+    """
+    cls.metadata.info.setdefault("managed models", set()).add(cls)  # type: ignore
+    return cls
+
+
+def register_object(cls: DeclarativeMeta, **kwargs) -> None:
+    """
+    Registers an object to be created during a database migration.
+
+    :param cls: The class of the declarative model class. This is used to determine which table to operate on.
+    :param kwargs: Arguments used to create the object. This must uniquely identify the object as it is also used to
+                  determine whether the object already exists.
+    """
+    cls.metadata.info.setdefault("objects", dict()).setdefault(cls, list()).append(kwargs)  # type: ignore
+
+
+@comparators.dispatch_for("schema")
+def compare_objects(autogen_context: AutogenContext, upgrade_ops: UpgradeOps, schemas: List[str]) -> None:
+    """
+    Generates appropriate data migrations for the `autogen_context` and adds them to `upgrade_ops`.
+    """
+    managed_models = autogen_context.metadata.info.get('managed models', set())
+    objects: Dict[DeclarativeMeta, Any] = autogen_context.metadata.info.get('objects', dict())
+    remaining_objects = {cls: set(cls.query.all())  # type: ignore
+                         for cls in objects.keys()
+                         if cls in managed_models
+                         and autogen_context.dialect.has_table(autogen_context.connection.engine,
+                                                               cls.__table__.name)}  # type: ignore
+
+    # Add new objects
+    for cls, datas in objects.items():
+        for data in datas:
+            existing_object = (cls.query.filter_by(**data).first()  # type: ignore
+                               if autogen_context.dialect.has_table(autogen_context.connection.engine,
+                                                                    cls.__table__.name)  # type: ignore
+                               else None)
+            if existing_object:
+                remaining_objects.get(cls, set()).discard(existing_object)
+            else:
+                print("Adding " + cls.__name__ + ": " + str(data))
+                upgrade_ops.ops.append(InsertRowOp(cls.__table__.name, **data))  # type: ignore
+
+    # Remove old objects
+    for cls, object_set in remaining_objects.items():
+        for o in object_set:
+            values = {key: getattr(o, key) for key in o.__mapper__.column_attrs.keys()}
+            print("Deleting " + cls.__name__ + ": " + str(values))
+            upgrade_ops.ops.append(DeleteRowOp(cls.__table__.name, **values))  # type: ignore