[FIX] web: fix bad groupby as str instead of list

A mistake introduced in  234db70d86, the
`groupby` of  `_read_group` should be list/tuple of  `str`, not a `str`.

closes odoo/odoo#119400

Signed-off-by: Raphael Collet <rco@odoo.com>

addons/web/models/models.py

@@ -185,7 +185,7 @@ class Base(models.AbstractModel):
         elif limit and len(groups) == limit:
             length = limit + len(self._read_group(
                 domain,
-                groupby=groupby if not lazy else groupby[0],
+                groupby=groupby if not lazy else [groupby[0]],
                 offset=limit,
                 order=orderby,
             ))

odoo/addons/test_new_api/tests/__init__.py

@@ -15,3 +15,4 @@ from . import test_domain
 from . import test_schema
 from . import test_company_checks
 from . import test_unity_read
+from . import test_web_read_group

odoo/addons/test_new_api/tests/test_web_read_group.py

@@ -0,0 +1,41 @@
+from odoo.tests.common import TransactionCase
+
+
+class TestWebReadGroup(TransactionCase):
+
+    @classmethod
+    def setUpClass(cls):
+        super().setUpClass()
+        cls.env['test_new_api.multi.tag'].create([
+            {'name': 'one'},
+            {'name': 'two'},
+            {'name': 'two'},
+            {'name': 'there'},
+            {'name': 'there'},
+            {'name': 'there'},
+        ])
+
+    def test_web_read_group_limit_not_reached(self):
+        result = self.env['test_new_api.multi.tag'].web_read_group(
+            [], ['__count'], ['name'], limit=80,
+        )
+        self.assertEqual(result, {
+            'groups': [
+                {'name': 'one', 'name_count': 1, '__domain': [('name', '=', 'one')]},
+                {'name': 'there', 'name_count': 3, '__domain': [('name', '=', 'there')]},
+                {'name': 'two', 'name_count': 2, '__domain': [('name', '=', 'two')]},
+            ],
+            'length': 3,
+        })
+
+    def test_web_read_group_limit_reached(self):
+        result = self.env['test_new_api.multi.tag'].web_read_group(
+            [], ['__count'], ['name'], limit=2,
+        )
+        self.assertEqual(result, {
+            'groups': [
+                {'name': 'one', 'name_count': 1, '__domain': [('name', '=', 'one')]},
+                {'name': 'there', 'name_count': 3, '__domain': [('name', '=', 'there')]},
+            ],
+            'length': 3,
+        })