Fix rendering of Column objects in dialect kwargs like postgresql_include

Fixes: #1258

Author: Ajaysingh-2003

alembic/autogenerate/render.py

@@ -306,8 +306,28 @@ def _drop_table(autogen_context: AutogenContext, op: ops.DropTableOp) -> str:
 def _render_dialect_kwargs_items(
     autogen_context: AutogenContext, dialect_kwargs: _DialectArgView
 ) -> list[str]:
+    def _render_kwarg_value(val: Any) -> str:
+        if isinstance(val, (list, tuple)):
+            rendered = [
+                (
+                    repr(_ident(getattr(item, "name", None)))
+                    if isinstance(item, sa_schema.Column)
+                    else _render_potential_expr(item, autogen_context)
+                )
+                for item in val
+            ]
+            if isinstance(val, tuple):
+                return "(%s%s)" % (
+                    ", ".join(rendered),
+                    "," if len(rendered) == 1 else "",
+                )
+            else:
+                return "[%s]" % ", ".join(rendered)
+        else:
+            return _render_potential_expr(val, autogen_context)
+
     return [
-        f"{key}={_render_potential_expr(val, autogen_context)}"
+        f"{key}={_render_kwarg_value(val)}"
         for key, val in dialect_kwargs.items()
     ]
 

docs/build/unreleased/1258.rst

@@ -0,0 +1,10 @@
+.. change::
+    :tags: bug, autogenerate
+    :tickets: 1258
+
+    Fixed rendering of dialect keyword arguments containing
+    :class:`~sqlalchemy.schema.Column` objects within sequences, such as
+    ``postgresql_include``.  These were previously rendered using ``repr()``,
+    producing invalid Python in the generated migration scripts.  Column
+    objects within list or tuple values are now correctly rendered as their
+    string column names.  Pull request courtesy Ajay Singh.

tests/test_autogen_render.py

@@ -147,6 +147,25 @@ def test_render_add_index_custom_kwarg(self):
             "['active', 'code'], unique=False, somedialect_foobar='option')",
         )
 
+    @testing.emits_warning("Can't validate argument ")
+    def test_render_add_index_dialect_kwarg_with_columns(self):
+        """test that Column objects in dialect kwargs like
+        postgresql_include are rendered as column name strings,
+        not as raw Column repr.
+        """
+        t = self.table()
+        idx = Index(
+            "test_active_code_idx",
+            t.c.active,
+            somedialect_include=(t.c.code,),
+        )
+        op_obj = ops.CreateIndexOp.from_index(idx)
+        eq_ignore_whitespace(
+            autogenerate.render_op_text(self.autogen_context, op_obj),
+            "op.create_index('test_active_code_idx', 'test', "
+            "['active'], unique=False, somedialect_include=('code',))",
+        )
+
     def test_render_add_index_batch(self):
         """
         autogenerate.render._add_index
@@ -316,6 +335,25 @@ def test_render_drop_index_custom_kwarg(self):
             "somedialect_foobar='option')",
         )
 
+    @testing.emits_warning("Can't validate argument ")
+    def test_render_drop_index_dialect_kwarg_with_columns(self):
+        """test that Column objects in dialect kwargs like
+        postgresql_include are rendered as column name strings
+        in drop_index, not as raw Column repr.
+        """
+        t = self.table()
+        idx = Index(
+            "test_active_code_idx",
+            t.c.active,
+            somedialect_include=(t.c.code,),
+        )
+        op_obj = ops.DropIndexOp.from_index(idx)
+        eq_ignore_whitespace(
+            autogenerate.render_op_text(self.autogen_context, op_obj),
+            "op.drop_index('test_active_code_idx', table_name='test', "
+            "somedialect_include=('code',))",
+        )
+
     def test_add_fk_constraint__dialect_kwargs(self):
         t1 = self.table()
         t2 = self.table()