add_to_dict(): Fix mapping of to_dict()

CHANGES

@@ -15,6 +15,9 @@ $ pip install --user --upgrade --pre unihan-db
 
 ### Bug fixes
 
+- SQLAlchemy: Fix `add_to_dict()` event mapper bug (#325)
+
+  This allows `Unhn` rows to use `row.as_dict()` once more.
 - Bump unihan-etl 0.30.0post0 -> 0.30.1
 
   Fix `kRSUnicode` double apostrophes.

examples/01_bootstrap.py

@@ -17,3 +17,5 @@
 random_row = random_row_query.first()
 
 pprint.pprint(bootstrap.to_dict(random_row))
+
+pprint.pprint(random_row.to_dict())  # type:ignore

src/unihan_db/bootstrap.py

@@ -6,7 +6,7 @@
 
 import sqlalchemy
 from sqlalchemy import create_engine, event
-from sqlalchemy.orm import Session, class_mapper, scoped_session, sessionmaker
+from sqlalchemy.orm import Mapper, Session, class_mapper, scoped_session, sessionmaker
 from sqlalchemy.orm.decl_api import registry
 from sqlalchemy.orm.scoping import ScopedSession
 
@@ -198,6 +198,12 @@ def bootstrap_unihan(
         log.info("Done adding rows.")
 
 
+@event.listens_for(Unhn, "before_mapper_configured", once=True)
+def setup_orm_mappings(mapper: Mapper[Base], class_: Base) -> None:
+    """Add special methods to Base declarative model used in Unihan DB."""
+    add_to_dict(class_)  # Add .to_dict() to rows returned
+
+
 def to_dict(obj: t.Any, found: t.Optional[t.Set[t.Any]] = None) -> t.Dict[str, object]:
     """Return dictionary of an SQLAlchemy Query result.
 
@@ -272,7 +278,6 @@ def get_session(
     engine_url = engine_url.format(**{"user_data_dir": dirs.user_data_dir})
     engine = create_engine(engine_url)
 
-    event.listen(mapper_reg, "after_configured", add_to_dict(Base))
     Base.metadata.create_all(bind=engine)
     session_factory = sessionmaker(bind=engine)
     session = scoped_session(session_factory)