[IMP] Allow to delete attachment without res_model

But allow it only if a file pattern is set, to avoid deleting all orphan attachments are some are auto-generated by Odoo

autovacuum_message_attachment/models/ir_attachment.py

@@ -30,7 +30,7 @@ class IrAttachment(models.Model):
         if rule.model_ids:
             models = rule.model_ids.mapped("model")
             domains.append([("res_model", "in", models)])
-        else:
+        elif not rule.empty_model or not rule.filename_pattern:
             # Avoid deleting attachment without model, if there are, it is
             # probably some attachments created by Odoo
             domains.append([("res_model", "!=", False)])

autovacuum_message_attachment/models/vacuum_rule.py

@@ -61,6 +61,10 @@ class VacuumRule(models.Model):
     )
     model_filter_domain = fields.Text()
     model = fields.Char(readonly=True, compute="_compute_model_id", string="Model code")
+    empty_model = fields.Boolean(
+        help="Take into account attachment not linked to any model, but only if a "
+        "pattern is set, to avoid deleting attachments generated/needed by odoo"
+    )
     message_type = fields.Selection(
         [
             ("email", "Email"),

autovacuum_message_attachment/views/rule_vacuum.xml

@@ -39,6 +39,10 @@
                         <group attrs="{'invisible': [('ttype', '!=', 'attachment')]}">
                             <field name="filename_pattern" />
                             <field name="inheriting_model" />
+                            <field
+                                name="empty_model"
+                                attrs="{'invisible': ['|', ('model_ids', '!=', []), ('filename_pattern', '=', False)]}"
+                            />
                         </group>
                         <group string="Models">
                             <field name="model_ids" nolabel="1" colspan="4" />