From caa9293e2e0d0b186a24962ad72b954271934913 Mon Sep 17 00:00:00 2001
From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Sat, 19 Nov 2022 16:42:22 -0500
Subject: add common base class for all SQL col expression objects

Added a new type :class:`.SQLColumnExpression` which may be indicated in
user code to represent any SQL column oriented expression, including both
those based on :class:`.ColumnElement` as well as on ORM
:class:`.QueryableAttribute`. This type is a real class, not an alias, so
can also be used as the foundation for other objects.

Fixes: #8847
Change-Id: I3161bdff1c9f447793fce87864e1774a90cd4146
---
 lib/sqlalchemy/sql/__init__.py   |  1 +
 lib/sqlalchemy/sql/elements.py   | 22 +++++++++++++++++++++-
 lib/sqlalchemy/sql/expression.py |  1 +
 3 files changed, 23 insertions(+), 1 deletion(-)

(limited to 'lib/sqlalchemy/sql')

diff --git a/lib/sqlalchemy/sql/__init__.py b/lib/sqlalchemy/sql/__init__.py
index 5702d6c25..8dae9c3f5 100644
--- a/lib/sqlalchemy/sql/__init__.py
+++ b/lib/sqlalchemy/sql/__init__.py
@@ -82,6 +82,7 @@ from .expression import Select as Select
 from .expression import select as select
 from .expression import Selectable as Selectable
 from .expression import SelectLabelStyle as SelectLabelStyle
+from .expression import SQLColumnExpression as SQLColumnExpression
 from .expression import StatementLambdaElement as StatementLambdaElement
 from .expression import Subquery as Subquery
 from .expression import table as table
diff --git a/lib/sqlalchemy/sql/elements.py b/lib/sqlalchemy/sql/elements.py
index d9a1a9358..914d2b326 100644
--- a/lib/sqlalchemy/sql/elements.py
+++ b/lib/sqlalchemy/sql/elements.py
@@ -1115,6 +1115,26 @@ class SQLCoreOperations(Generic[_T], ColumnOperators, TypingOnly):
             ...
 
 
+class SQLColumnExpression(
+    SQLCoreOperations[_T], roles.ExpressionElementRole[_T], TypingOnly
+):
+    """A type that may be used to indicate any SQL column element or object
+    that acts in place of one.
+
+    :class:`.SQLColumnExpression` is a base of
+    :class:`.ColumnElement`, as well as within the bases of ORM elements
+    such as :class:`.InstrumentedAttribute`, and may be used in :pep:`484`
+    typing to indicate arguments or return values that should behave
+    as column expressions.
+
+    .. versionadded:: 2.0.0b4
+
+
+    """
+
+    __slots__ = ()
+
+
 _SQO = SQLCoreOperations
 
 SelfColumnElement = TypeVar("SelfColumnElement", bound="ColumnElement[Any]")
@@ -1131,7 +1151,7 @@ class ColumnElement(
     roles.DMLColumnRole,
     roles.DDLConstraintColumnRole,
     roles.DDLExpressionRole,
-    SQLCoreOperations[_T],
+    SQLColumnExpression[_T],
     DQLDMLClauseElement,
 ):
     """Represent a column-oriented SQL expression suitable for usage in the
diff --git a/lib/sqlalchemy/sql/expression.py b/lib/sqlalchemy/sql/expression.py
index d08bbf4eb..2498bfb37 100644
--- a/lib/sqlalchemy/sql/expression.py
+++ b/lib/sqlalchemy/sql/expression.py
@@ -95,6 +95,7 @@ from .elements import quoted_name as quoted_name
 from .elements import ReleaseSavepointClause as ReleaseSavepointClause
 from .elements import RollbackToSavepointClause as RollbackToSavepointClause
 from .elements import SavepointClause as SavepointClause
+from .elements import SQLColumnExpression as SQLColumnExpression
 from .elements import TextClause as TextClause
 from .elements import True_ as True_
 from .elements import Tuple as Tuple
-- 
cgit v1.2.1