[IMP] core: allow set [value] in selection ondelete

In some cases we migh want to change to a value that isn't the default
one when uninstalling.
For instance: when we uninstall the module `event_sale`, a product has
the field `detailed_type` set to `event`, which is a subtype of `service`.
So we want to update the value to `service` when uninstalling instead of
the default value, which would be `consu` and wouldn't make any sense.

Part-of: odoo/odoo#77876

odoo/addons/base/models/ir_model.py

@@ -1435,6 +1435,8 @@ class IrModelSelection(models.Model):
             elif ondelete == 'set default':
                 value = field.convert_to_write(field.default(Model), Model)
                 safe_write(selection._get_records(), field.name, value)
+            elif ondelete.startswith('set '):
+                safe_write(selection._get_records(), field.name, ondelete[4:])
             elif ondelete == 'cascade':
                 selection._get_records().unlink()
             else:

odoo/addons/test_new_api/models/test_new_api.py

@@ -1179,7 +1179,7 @@ class SelectionRequiredLiteral(models.Model):
 
     my_selection = fields.Selection(selection_add=[
         ('bacon', "Bacon"),
-    ], ondelete={'bacon': lambda r: r.write({'my_selection': 'bar'})})
+    ], ondelete={'bacon': 'set bar'})
 
 
 class SelectionRequiredMultiple(models.Model):

odoo/addons/test_new_api/tests/test_new_fields.py

@@ -315,10 +315,10 @@ class TestFields(TransactionCaseWithUserDemo):
         check_stored(discussion1)
 
         # switch message from discussion, and check again
-        
+
         # See YTI FIXME
         discussion1.invalidate_cache()
-        
+
         discussion2 = discussion1.copy({'name': 'Another discussion'})
         message2 = discussion1.messages[0]
         message2.discussion = discussion2
@@ -3132,6 +3132,20 @@ class TestSelectionOndeleteAdvanced(common.TransactionCase):
         with self.assertRaises(AssertionError):
             self.registry.setup_models(self.env.cr)
 
+    def test_ondelete_value_no_valid(self):
+        class Foo(models.Model):
+            _module = None
+            _inherit = self.MODEL_BASE
+
+            my_selection = fields.Selection(selection_add=[
+                ('westvleteren', "Westvleteren beers is overrated"),
+            ], ondelete={'westvleteren': 'set foooo'})
+
+        Foo._build_model(self.registry, self.env.cr)
+
+        with self.assertRaises(AssertionError):
+            self.registry.setup_models(self.env.cr)
+
     def test_ondelete_required_null_explicit(self):
         class Foo(models.Model):
             _module = None

odoo/fields.py

@@ -2347,6 +2347,8 @@ class Selection(Field):
               deleted along with the option itself.
             - 'set default' -- all records with this option will be
               set to the default of the field definition
+            - 'set VALUE' -- all records with this option will be
+              set to the given value
             - <callable> -- a callable whose first and only argument will be
               the set of records containing the specified Selection option,
               for custom processing
@@ -2444,12 +2446,17 @@ class Selection(Field):
                             "as it does not define a default! Either define one in the base "
                             "field, or change the chosen ondelete policy" % self
                         )
-                        continue
-                    raise ValueError(
-                        "%r: ondelete policy %r for selection value %r is not a valid ondelete "
-                        "policy, please choose one of 'set null', 'set default', 'cascade' or "
-                        "a callable" % (self, val, key)
-                    )
+                    elif val.startswith('set '):
+                        assert val[4:] in values, (
+                            "%s: ondelete policy of type 'set %%' must be either 'set null', "
+                            "'set default', or 'set value' where value is a valid selection value."
+                        ) % self
+                    else:
+                        raise ValueError(
+                            "%r: ondelete policy %r for selection value %r is not a valid ondelete"
+                            " policy, please choose one of 'set null', 'set default', "
+                            "'set [value]', 'cascade' or a callable" % (self, val, key)
+                        )
 
                 values = merge_sequences(values, [kv[0] for kv in selection_add])
                 labels.update(kv for kv in selection_add if len(kv) == 2)