Milestone 3

backend/alembic/env.py

@@ -0,0 +1,76 @@
+"""Alembic environment.
+
+We bypass `alembic.ini`'s `sqlalchemy.url` and pull the URL from the project's
+Pydantic settings so a single .env governs both runtime and migrations.
+
+Importing `app.models` registers every model on `Base.metadata`.
+"""
+
+from __future__ import annotations
+
+from logging.config import fileConfig
+
+from alembic import context
+from sqlalchemy import engine_from_config, pool
+
+# noqa: F401 — registers models on Base.metadata
+from app import models as _models  # noqa: F401
+from app.core.config import settings
+from app.db.base import Base
+
+config = context.config
+
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# Inject the DB URL at runtime.
+config.set_main_option("sqlalchemy.url", settings.database_url)
+
+target_metadata = Base.metadata
+
+
+def include_object(_object, _name, type_, _reflected, _compare_to):  # type: ignore[no-untyped-def]
+    """Skip alembic's internal version table from autogenerate diffs."""
+    if type_ == "table" and _name == "alembic_version":
+        return False
+    return True
+
+
+def run_migrations_offline() -> None:
+    """Generate SQL without an engine — useful for review."""
+    context.configure(
+        url=config.get_main_option("sqlalchemy.url"),
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+        include_object=include_object,
+        compare_type=True,
+        compare_server_default=True,
+    )
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online() -> None:
+    """Apply migrations against a live DB."""
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata,
+            include_object=include_object,
+            compare_type=True,
+            compare_server_default=True,
+        )
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()