reorganize Mapped[] super outside of MapperProperty

We made all the MapperProperty classes a subclass
of Mapped[] to allow declarative mappings to name
Mapped[] on the left side.  this was cheating a bit because
MapperProperty is not actually a descriptor, and the mapping
process replaces the object with InstrumentedAttribute at
mapping time, which is the actual Mapped[] descriptor.

But now in I6929f3da6e441cad92285e7309030a9bac4e429d we
are considering making the "cheating" a little more extensive
by putting DynamicMapped / WriteOnlyMapped in Relationship's
hierarchy, which need a flat out "type: ignore" to work.

Instead of pushing more cheats into the core classes, move
out the "Declarative"-facing versions of these classes to be
typing only: Relationship, Composite, Synonym, and MappedSQLExpression
added for ColumnProperty.  Keep the internals expressed on the
old names, RelationshipProperty, CompositeProperty, SynonymProperty,
ColumnProprerty, which will remain "pure" with fully correct typing.
then have the typing only endpoints be where the "cheating"
and "type: ignores" have to happen, so that these are more or less
slightly better forms of "Any".

Change-Id: Ied7cc11196c9204da6851f49593d1b1fd2ef8ad8

1 files changed, 5 insertions, 5 deletions

diff --git a/lib/sqlalchemy/orm/decl_base.py b/lib/sqlalchemy/orm/decl_base.py
index e8d6e4c1b..a383e92ca 100644
--- a/lib/sqlalchemy/orm/decl_base.py
+++ b/lib/sqlalchemy/orm/decl_base.py
@@ -40,8 +40,8 @@ from .attributes import InstrumentedAttribute
 from .attributes import QueryableAttribute
 from .base import _is_mapped_class
 from .base import InspectionAttr
-from .descriptor_props import Composite
-from .descriptor_props import Synonym
+from .descriptor_props import CompositeProperty
+from .descriptor_props import SynonymProperty
 from .interfaces import _AttributeOptions
 from .interfaces import _IntrospectsAnnotations
 from .interfaces import _MappedAttribute
@@ -1211,7 +1211,7 @@ class _ClassScanMapperConfig(_MapperConfig):
             ):
                 # detect a QueryableAttribute that's already mapped being
                 # assigned elsewhere in userland, turn into a synonym()
-                value = Synonym(value.key)
+                value = SynonymProperty(value.key)
                 setattr(cls, k, value)
 
             if (
@@ -1316,7 +1316,7 @@ class _ClassScanMapperConfig(_MapperConfig):
                     del our_stuff[key]
 
                 for col in c.columns_to_assign:
-                    if not isinstance(c, Composite):
+                    if not isinstance(c, CompositeProperty):
                         name_to_prop_key[col.name].add(key)
                     declared_columns.add(col)
 
@@ -1736,7 +1736,7 @@ def _add_attribute(
         elif isinstance(value, QueryableAttribute) and value.key != key:
             # detect a QueryableAttribute that's already mapped being
             # assigned elsewhere in userland, turn into a synonym()
-            value = Synonym(value.key)
+            value = SynonymProperty(value.key)
             mapped_cls.__mapper__.add_property(key, value)
         else:
             type.__setattr__(cls, key, value)