GH-4: Introduce Alembic for database migrations

alembic.ini

@@ -0,0 +1,2 @@
+[alembic]
+script_location = schemes:migrations

pyproject.toml

@@ -4,6 +4,7 @@ version = "1.0.0"
 description = "ATE Schemes App."
 requires-python = ">=3.11"
 dependencies = [
+    "alembic~=1.12.0",
     "authlib~=1.2.0",
     "flask~=2.3.0",
     "govuk-frontend-jinja~=2.7.0",

schemes/__init__.py

@@ -1,17 +1,19 @@
 import os
 from typing import Any, Mapping
 
+import alembic.config
 import inject
+from alembic import command
 from authlib.integrations.flask_client import OAuth
 from authlib.oauth2.rfc7523 import PrivateKeyJWT
 from flask import Config, Flask, Response, render_template, request, url_for
 from inject import Binder
 from jinja2 import ChoiceLoader, FileSystemLoader, PackageLoader, PrefixLoader
-from sqlalchemy import Engine, MetaData, create_engine
+from sqlalchemy import Engine, create_engine
 
 from schemes import api, auth, home, start
 from schemes.config import DevConfig
-from schemes.users import DatabaseUserRepository, User, UserRepository, add_tables
+from schemes.users import DatabaseUserRepository, User, UserRepository
 
 
 def create_app(test_config: Mapping[str, Any] | None = None) -> Flask:
@@ -107,11 +109,14 @@ def _configure_oidc(app: Flask) -> None:
 
 
 def _create_database() -> None:
-    metadata = MetaData()
-    add_tables(metadata)
-
     engine = inject.instance(Engine)
-    metadata.create_all(engine)
+
+    alembic_config = alembic.config.Config()
+    alembic_config.set_main_option("script_location", "schemes:migrations")
+
+    with engine.connect() as connection:
+        alembic_config.attributes["connection"] = connection
+        command.upgrade(alembic_config, "head")
 
 
 def _configure_users() -> None:

schemes/migrations/env.py

@@ -0,0 +1,7 @@
+from alembic import context
+
+connection = context.config.attributes["connection"]
+context.configure(connection=connection, target_metadata=None)
+
+with context.begin_transaction():
+    context.run_migrations()

schemes/migrations/script.py.mako

@@ -0,0 +1,24 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = ${repr(up_revision).replace("'", '"')}
+down_revision: Union[str, None] = ${repr(down_revision).replace("'", '"')}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels).replace("'", '"')}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on).replace("'", '"')}
+
+
+def upgrade() -> None:
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    ${downgrades if downgrades else "pass"}

schemes/migrations/versions/bfc3cbc1bb13_create_users_table.py

@@ -0,0 +1,28 @@
+"""Create users table
+
+Revision ID: bfc3cbc1bb13
+Revises: 
+Create Date: 2023-10-20 10:15:51.912421
+
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "bfc3cbc1bb13"
+down_revision: Union[str, None] = None
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "users",
+        sa.Column("id", sa.Integer, primary_key=True),
+        sa.Column("email", sa.String(256), nullable=False, unique=True),
+    )
+
+
+def downgrade() -> None:
+    op.drop_table("users")