Catalog seeding, blank-unique fix, slides rotation, console repair

shopdb/__init__.py

@@ -88,6 +88,12 @@ def create_app(config_name: str = None) -> Flask:
     # Initialize extensions
     init_extensions(app)
 
+    # An optional unique column accepts any number of NULLs but exactly one
+    # empty string, so a second blank code collided and became a 500. Normalise
+    # blank to NULL once, at the mapper, rather than in each endpoint.
+    from .utils.blankunique import register_blank_unique_normaliser
+    register_blank_unique_normaliser()
+
     # Initialize plugin manager
     with app.app_context():
         plugin_manager.init_app(app, db)
@@ -186,6 +192,31 @@ def register_error_handlers(app: Flask):
     from .utils.responses import error_response, ErrorCodes
     from .exceptions import ShopDBException
 
+    # A uniqueness violation is the caller's problem, not a server fault. Without
+    # this it surfaced as a bare 500 with a SQLAlchemy traceback in the log and
+    # nothing usable on screen - the operator saw "internal server error" for
+    # having reused a code that was already taken.
+    from sqlalchemy.exc import IntegrityError
+
+    @app.errorhandler(IntegrityError)
+    def handle_integrity_error(error):
+        from .extensions import db
+        db.session.rollback()
+        message = str(getattr(error, 'orig', error))
+        app.logger.warning('integrity error: %s', message)
+        if 'Duplicate entry' in message or 'UNIQUE constraint' in message:
+            return error_response(
+                ErrorCodes.CONFLICT,
+                'That value is already in use. Codes and identifiers must be unique.',
+                http_code=409)
+        if 'foreign key constraint' in message.lower():
+            return error_response(
+                ErrorCodes.VALIDATION_ERROR,
+                'That record refers to something that does not exist, or is still in use elsewhere.',
+                http_code=400)
+        return error_response(ErrorCodes.VALIDATION_ERROR,
+                              'The database rejected that change.', http_code=400)
+
     @app.errorhandler(ShopDBException)
     def handle_shopdb_exception(error):
         http_codes = {