Wrap dataclass exceptions clarifying origin

Exceptions such as ``TypeError`` and ``ValueError`` raised by Python
dataclasses when making use of the :class:`_orm.MappedAsDataclass` mixin
class or :meth:`_orm.registry.mapped_as_dataclass` decorator are now
wrapped within an :class:`.InvalidRequestError` wrapper along with
informative context about the error message, referring to the Python
dataclasses documentation as the authoritative source of background
information on the cause of the exception.

Fixes: #9563
Change-Id: I25652485b91c4ee8cf112b91aae8f9041061a8bd

1 files changed, 8 insertions, 0 deletions

diff --git a/lib/sqlalchemy/orm/decl_base.py b/lib/sqlalchemy/orm/decl_base.py
index 828501d8c..bd62c3c1b 100644
--- a/lib/sqlalchemy/orm/decl_base.py
+++ b/lib/sqlalchemy/orm/decl_base.py
@@ -1210,6 +1210,14 @@ class _ClassScanMapperConfig(_MapperConfig):
                     if v is not _NoArg.NO_ARG and k != "dataclass_callable"
                 },
             )
+        except (TypeError, ValueError) as ex:
+            raise exc.InvalidRequestError(
+                f"Python dataclasses error encountered when creating "
+                f"dataclass for {klass.__name__!r}: "
+                f"{ex!r}. Please refer to Python dataclasses "
+                "documentation for additional information.",
+                code="dcte",
+            ) from ex
         finally:
             # restore original annotations outside of the dataclasses
             # process; for mixins and __abstract__ superclasses, SQLAlchemy