establish column_property and query_expression as readonly from a dc perspective

Fixed bug in ORM Declarative Dataclasses where the
:func:`_orm.queryable_attribute` and :func:`_orm.column_property`
constructs, which are documented as read-only constructs in the context of
a Declarative mapping, could not be used with a
:class:`_orm.MappedAsDataclass` class without adding ``init=False``, which
in the case of :func:`_orm.queryable_attribute` was not possible as no
``init`` parameter was included. These constructs have been modified from a
dataclass perspective to be assumed to be "read only", setting
``init=False`` by default and no longer including them in the pep-681
constructor. The dataclass parameters for :func:`_orm.column_property`
``init``, ``default``, ``default_factory``, ``kw_only`` are now deprecated;
these fields don't apply to :func:`_orm.column_property` as used in a
Declarative dataclasses configuration where the construct would be
read-only. Also added read-specific parameter
:paramref:`_orm.queryable_attribute.compare` to
:func:`_orm.queryable_attribute`; :paramref:`_orm.queryable_attribute.repr`
was already present.

Added missing :paramref:`_orm.mapped_column.active_history` parameter
to :func:`_orm.mapped_column` construct.

Fixes: #9628
Change-Id: I2ab44d6b763b20410bd1ebb5ac949a6d223f1ce2

1 files changed, 11 insertions, 4 deletions

diff --git a/lib/sqlalchemy/orm/properties.py b/lib/sqlalchemy/orm/properties.py
index 2f7b85d88..f00775874 100644
--- a/lib/sqlalchemy/orm/properties.py
+++ b/lib/sqlalchemy/orm/properties.py
@@ -151,8 +151,12 @@ class ColumnProperty(
         info: Optional[_InfoType] = None,
         doc: Optional[str] = None,
         _instrument: bool = True,
+        _assume_readonly_dc_attributes: bool = False,
     ):
-        super().__init__(attribute_options=attribute_options)
+        super().__init__(
+            attribute_options=attribute_options,
+            _assume_readonly_dc_attributes=_assume_readonly_dc_attributes,
+        )
         columns = (column,) + additional_columns
         self.columns = [
             coercions.expect(roles.LabeledColumnExprRole, c) for c in columns
@@ -532,6 +536,7 @@ class MappedColumn(
         "deferred",
         "deferred_group",
         "deferred_raiseload",
+        "active_history",
         "_attribute_options",
         "_has_dataclass_arguments",
         "_use_existing_column",
@@ -579,7 +584,7 @@ class MappedColumn(
             self.deferred = bool(
                 self.deferred_group or self.deferred_raiseload
             )
-
+        self.active_history = kw.pop("active_history", False)
         self._sort_order = kw.pop("sort_order", 0)
         self.column = cast("Column[_T]", Column(*arg, **kw))
         self.foreign_keys = self.column.foreign_keys
@@ -597,6 +602,7 @@ class MappedColumn(
         new.deferred_group = self.deferred_group
         new.deferred_raiseload = self.deferred_raiseload
         new.foreign_keys = new.column.foreign_keys
+        new.active_history = self.active_history
         new._has_nullable = self._has_nullable
         new._attribute_options = self._attribute_options
         new._has_insert_default = self._has_insert_default
@@ -612,13 +618,14 @@ class MappedColumn(
 
     @property
     def mapper_property_to_assign(self) -> Optional[MapperProperty[_T]]:
-        if self.deferred:
+        if self.deferred or self.active_history:
             return ColumnProperty(
                 self.column,
-                deferred=True,
+                deferred=self.deferred,
                 group=self.deferred_group,
                 raiseload=self.deferred_raiseload,
                 attribute_options=self._attribute_options,
+                active_history=self.active_history,
             )
         else:
             return None