pep-484: ORM public API, constructors

for the moment, abandoning using @overload with
relationship() and mapped_column().  The overloads
are very difficult to get working at all, and
the overloads that were there all wouldn't pass on
mypy.  various techniques of getting them to
"work", meaning having right hand side dictate
what's legal on the left, have mixed success
and wont give consistent results; additionally,
it's legal to have Optional / non-optional
independent of nullable in any case for columns.
relationship cases are less ambiguous but mypy
was not going along with things.

we have a comprehensive system of allowing
left side annotations to drive the right side,
in the absense of explicit settings on the right.
so type-centric SQLAlchemy will be left-side
driven just like dataclasses, and the various flags
and switches on the right side will just not be
needed very much.

in other matters, one surprise, forgot to remove string support
from orm.join(A, B, "somename") or do deprecations
for it in 1.4.   This is a really not-directly-used
structure barely
mentioned in the docs for many years, the example
shows a relationship being used, not a string, so
we will just change it to raise the usual error here.

Change-Id: Iefbbb8d34548b538023890ab8b7c9a5d9496ec6e

1 files changed, 5 insertions, 3 deletions

diff --git a/lib/sqlalchemy/orm/attributes.py b/lib/sqlalchemy/orm/attributes.py
index 33ce96a19..41d944c57 100644
--- a/lib/sqlalchemy/orm/attributes.py
+++ b/lib/sqlalchemy/orm/attributes.py
@@ -44,7 +44,7 @@ from .base import instance_dict as instance_dict
 from .base import instance_state as instance_state
 from .base import instance_str
 from .base import LOAD_AGAINST_COMMITTED
-from .base import manager_of_class
+from .base import manager_of_class as manager_of_class
 from .base import Mapped as Mapped  # noqa
 from .base import NEVER_SET  # noqa
 from .base import NO_AUTOFLUSH
@@ -52,6 +52,7 @@ from .base import NO_CHANGE  # noqa
 from .base import NO_RAISE
 from .base import NO_VALUE
 from .base import NON_PERSISTENT_OK  # noqa
+from .base import opt_manager_of_class as opt_manager_of_class
 from .base import PASSIVE_CLASS_MISMATCH  # noqa
 from .base import PASSIVE_NO_FETCH
 from .base import PASSIVE_NO_FETCH_RELATED  # noqa
@@ -74,6 +75,7 @@ from ..sql import traversals
 from ..sql import visitors
 
 if TYPE_CHECKING:
+    from .interfaces import MapperProperty
     from .state import InstanceState
     from ..sql.dml import _DMLColumnElement
     from ..sql.elements import ColumnElement
@@ -146,7 +148,7 @@ class QueryableAttribute(
         self._of_type = of_type
         self._extra_criteria = extra_criteria
 
-        manager = manager_of_class(class_)
+        manager = opt_manager_of_class(class_)
         # manager is None in the case of AliasedClass
         if manager:
             # propagate existing event listeners from
@@ -370,7 +372,7 @@ class QueryableAttribute(
         return "%s.%s" % (self.class_.__name__, self.key)
 
     @util.memoized_property
-    def property(self):
+    def property(self) -> MapperProperty[_T]:
         """Return the :class:`.MapperProperty` associated with this
         :class:`.QueryableAttribute`.