Fix ModuleNotFoundError for asyncpg by normalizing async DB URLs to psycopg2

Agent-Logs-Url: https://github.com/christianlouis/dmarq/sessions/d1890838-1770-4d5f-886f-f210df761fae

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

backend/alembic/env.py

@@ -18,7 +18,9 @@ if config.config_file_name is not None:
 # Override sqlalchemy.url with DATABASE_URL environment variable when present
 database_url = os.environ.get("DATABASE_URL")
 if database_url:
-    config.set_main_option("sqlalchemy.url", database_url)
+    from app.core.database import _make_sync_db_url  # noqa: E402
+
+    config.set_main_option("sqlalchemy.url", _make_sync_db_url(database_url))
 
 # Import all models so that autogenerate can detect them
 from app.core.database import Base  # noqa: E402

backend/app/core/database.py

@@ -1,4 +1,5 @@
 from typing import Generator
+from urllib.parse import urlparse, urlunparse
 
 from sqlalchemy import create_engine
 from sqlalchemy.ext.declarative import declarative_base
@@ -6,10 +7,33 @@ from sqlalchemy.orm import sessionmaker
 
 from app.core.config import get_settings
 
+_ASYNC_TO_SYNC_SCHEMES = {
+    "postgresql+asyncpg": "postgresql+psycopg2",
+}
+
+
+def _make_sync_db_url(url: str) -> str:
+    """Return the synchronous-driver equivalent of *url*.
+
+    Kubernetes and docker-compose deployments sometimes configure DATABASE_URL
+    with an async driver scheme (e.g. ``postgresql+asyncpg://``).  Alembic and
+    the synchronous SQLAlchemy engine used here require a sync driver, so we
+    map known async schemes to their psycopg2 equivalents.
+
+    Only the scheme component of the URL is rewritten; all other parts
+    (credentials, host, path, query) are left untouched.
+    """
+    parsed = urlparse(url)
+    sync_scheme = _ASYNC_TO_SYNC_SCHEMES.get(parsed.scheme)
+    if sync_scheme is None:
+        return url
+    return urlunparse(parsed._replace(scheme=sync_scheme))
+
+
 settings = get_settings()
 
-# Configure SQLAlchemy
+# Configure SQLAlchemy (normalise async driver schemes to their sync equivalents)
-engine = create_engine(settings.DATABASE_URL, pool_pre_ping=True)
+engine = create_engine(_make_sync_db_url(settings.DATABASE_URL), pool_pre_ping=True)
 SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
 
 # Create base class for SQLAlchemy models

backend/app/tests/test_config.py

@@ -7,6 +7,7 @@ could run (see: pydantic_settings sources/providers/env.py decode_complex_value)
 """
 
 from app.core.config import Settings
+from app.core.database import _make_sync_db_url
 
 
 class TestBackendCorsOriginsValidator:
@@ -64,3 +65,34 @@ class TestBackendCorsOriginsValidator:
             "https://a.example.com",
             "https://b.example.com",
         ]
+
+
+class TestMakeSyncDbUrl:
+    """Tests for the _make_sync_db_url() URL normalization helper."""
+
+    def test_asyncpg_replaced_with_psycopg2(self):
+        """asyncpg scheme is converted to psycopg2."""
+        url = "postgresql+asyncpg://user:pass@db:5432/mydb"
+        assert _make_sync_db_url(url) == "postgresql+psycopg2://user:pass@db:5432/mydb"
+
+    def test_plain_postgresql_unchanged(self):
+        """Plain postgresql:// URLs are not modified."""
+        url = "postgresql://user:pass@db:5432/mydb"
+        assert _make_sync_db_url(url) == url
+
+    def test_psycopg2_url_unchanged(self):
+        """URLs already using psycopg2 are not modified."""
+        url = "postgresql+psycopg2://user:pass@db:5432/mydb"
+        assert _make_sync_db_url(url) == url
+
+    def test_sqlite_url_unchanged(self):
+        """SQLite URLs are not modified."""
+        url = "sqlite:///./dmarq.db"
+        assert _make_sync_db_url(url) == url
+
+    def test_database_url_setting_asyncpg(self):
+        """Settings with an asyncpg DATABASE_URL still initialise correctly."""
+        settings = Settings(DATABASE_URL="postgresql+asyncpg://user:pass@db:5432/mydb")
+        assert settings.DATABASE_URL == "postgresql+asyncpg://user:pass@db:5432/mydb"
+        # Normalised URL used by the engine must not contain asyncpg
+        assert "asyncpg" not in _make_sync_db_url(settings.DATABASE_URL)