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, 15 insertions, 4 deletions

diff --git a/lib/sqlalchemy/orm/decl_base.py b/lib/sqlalchemy/orm/decl_base.py
index 804d05ce1..9c79a4172 100644
--- a/lib/sqlalchemy/orm/decl_base.py
+++ b/lib/sqlalchemy/orm/decl_base.py
@@ -12,6 +12,8 @@ import collections
 from typing import Any
 from typing import Dict
 from typing import Tuple
+from typing import Type
+from typing import TYPE_CHECKING
 import weakref
 
 from . import attributes
@@ -42,6 +44,10 @@ from ..sql.schema import Column
 from ..sql.schema import Table
 from ..util import topological
 
+if TYPE_CHECKING:
+    from ._typing import _O
+    from ._typing import _RegistryType
+
 
 def _declared_mapping_info(cls):
     # deferred mapping
@@ -121,7 +127,7 @@ def _dive_for_cls_manager(cls):
         return None
 
     for base in cls.__mro__:
-        manager = attributes.manager_of_class(base)
+        manager = attributes.opt_manager_of_class(base)
         if manager:
             return manager
     return None
@@ -171,7 +177,7 @@ class _MapperConfig:
 
     @classmethod
     def setup_mapping(cls, registry, cls_, dict_, table, mapper_kw):
-        manager = attributes.manager_of_class(cls)
+        manager = attributes.opt_manager_of_class(cls)
         if manager and manager.class_ is cls_:
             raise exc.InvalidRequestError(
                 "Class %r already has been " "instrumented declaratively" % cls
@@ -191,7 +197,12 @@ class _MapperConfig:
 
         return cfg_cls(registry, cls_, dict_, table, mapper_kw)
 
-    def __init__(self, registry, cls_, mapper_kw):
+    def __init__(
+        self,
+        registry: _RegistryType,
+        cls_: Type[Any],
+        mapper_kw: Dict[str, Any],
+    ):
         self.cls = util.assert_arg_type(cls_, type, "cls_")
         self.classname = cls_.__name__
         self.properties = util.OrderedDict()
@@ -206,7 +217,7 @@ class _MapperConfig:
                 init_method=registry.constructor,
             )
         else:
-            manager = attributes.manager_of_class(self.cls)
+            manager = attributes.opt_manager_of_class(self.cls)
             if not manager or not manager.is_mapped:
                 raise exc.InvalidRequestError(
                     "Class %s has no primary mapper configured.  Configure "