coerce elements in mapper.primary_key, process in __mapper_args__

Repaired ORM Declarative mappings to allow for the
:paramref:`_orm.Mapper.primary_key` parameter to be specified within
``__mapper_args__`` when using :func:`_orm.mapped_column`. Despite this
usage being directly in the 2.0 documentation, the :class:`_orm.Mapper` was
not accepting the :func:`_orm.mapped_column` construct in this context. Ths
feature was already working for the :paramref:`_orm.Mapper.version_id_col`
and :paramref:`_orm.Mapper.polymorphic_on` parameters.

As part of this change, the ``__mapper_args__`` attribute may be specified
without using :func:`_orm.declared_attr` on a non-mapped mixin class,
including a ``"primary_key"`` entry that refers to :class:`_schema.Column`
or :func:`_orm.mapped_column` objects locally present on the mixin;
Declarative will also translate these columns into the correct ones for a
particular mapped class. This again was working already for the
:paramref:`_orm.Mapper.version_id_col` and
:paramref:`_orm.Mapper.polymorphic_on` parameters.  Additionally,
elements within ``"primary_key"`` may be indicated as string names of
existing mapped properties.

Fixes: #9240
Change-Id: Ie2000273289fa23e0af21ef9c6feb3962a8b848c

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/sqlalchemy/orm/decl_base.py b/lib/sqlalchemy/orm/decl_base.py
index a858f12cb..37fa964b8 100644
--- a/lib/sqlalchemy/orm/decl_base.py
+++ b/lib/sqlalchemy/orm/decl_base.py
@@ -1721,6 +1721,12 @@ class _ClassScanMapperConfig(_MapperConfig):
                 v = mapper_args[k]
                 mapper_args[k] = self.column_copies.get(v, v)
 
+        if "primary_key" in mapper_args:
+            mapper_args["primary_key"] = [
+                self.column_copies.get(v, v)
+                for v in util.to_list(mapper_args["primary_key"])
+            ]
+
         if "inherits" in mapper_args:
             inherits_arg = mapper_args["inherits"]
             if isinstance(inherits_arg, Mapper):