Function _copy_expression

lib/sqlalchemy/sql/schema.py:185–211

(
    expression: ColumnElement[Any],
    source_table: Optional[Table],
    target_table: Optional[Table],
)

# this should really be in sql/util.py but we'd have to
# break an import cycle
def _copy_expression(
    expression: ColumnElement[Any],
    source_table: Optional[Table],
    target_table: Optional[Table],
) -> ColumnElement[Any]:
    if source_table is None or target_table is None:
        return expression

    fixed_source_table = source_table
    fixed_target_table = target_table

    def replace(
        element: ExternallyTraversible, **kw: Any
    ) -> Optional[ExternallyTraversible]:
        if (
            isinstance(element, Column)
            and element.table is fixed_source_table
            and element.key in fixed_source_table.c
        ):
            return fixed_target_table.c[element.key]
        else:
            return None

    return cast(
        ColumnElement[Any],
        visitors.replacement_traverse(expression, {}, replace),
    )


@inspection._self_inspects