[FIX] account: Send & Print - prevent multi email if no mail template set

We don't want to allow to send multiple invoices by email if there is
no mail template set. It would lead to unwanted behaviors.

closes odoo/odoo#139612

Related: odoo/enterprise#49477
Signed-off-by: Laurent Smet (las) <las@odoo.com>

addons/account/tests/test_account_move_send.py

@@ -888,8 +888,8 @@ class TestAccountMoveSend(TestAccountMoveSendCommon):
         self.assertFalse(invoice.invoice_pdf_report_id)
         self.assertTrue(invoice.message_main_attachment_id)
 
-    def test_with_empty_mail_template(self):
-        """ Test you can use the send & print wizard without any mail template. """
+    def test_with_empty_mail_template_single(self):
+        """ Test you can use the send & print wizard without any mail template if and only if you are in single mode. """
         self.partner_a.email = "turlututu@tsointsoin"
         invoice = self.init_invoice("out_invoice", amounts=[1000], post=True)
 
@@ -900,6 +900,18 @@ class TestAccountMoveSend(TestAccountMoveSendCommon):
         message = self.env['mail.message'].search([('model', '=', invoice._name), ('res_id', '=', invoice.id)], limit=1)
         self.assertRecordValues(message, [{'subject': custom_subject}])
 
+    def test_with_empty_mail_template_multi(self):
+        """ Test shouldn't be able to send email without mail template in multi mode. """
+        self.partner_a.email = "turlututu@tsointsoin"
+        invoice_1 = self.init_invoice("out_invoice", amounts=[1000], post=True)
+        invoice_2 = self.init_invoice("out_invoice", amounts=[1000], post=True)
+
+        custom_subject = "turlututu"
+        wizard = self.create_send_and_print((invoice_1 + invoice_2), mail_template_id=None, mail_subject=custom_subject)
+
+        with self.assertRaises(UserError):
+            wizard.action_send_and_print(allow_fallback_pdf=True)
+
     def test_with_draft_invoices(self):
         """ Use Send & Print wizard on draft invoice(s) should raise an error. """
         invoice_posted = self.init_invoice("out_invoice", amounts=[1000], post=True)

addons/account/wizard/account_move_send.py

@@ -653,6 +653,10 @@ class AccountMoveSend(models.TransientModel):
                                     proforma PDF report instead.
         """
         self.ensure_one()
+
+        if self.mode == 'invoice_multi' and self.checkbox_send_mail and not self.mail_template_id:
+            raise UserError(_('Please select a mail template to send multiple invoices.'))
+
         force_synchronous = force_synchronous or self.checkbox_download
         process_later = self.mode == 'invoice_multi' and not force_synchronous
         if process_later:

addons/account/wizard/account_move_send_views.xml

@@ -80,6 +80,7 @@
                         </group>
                         <group>
                             <field name="mail_template_id"
+                                   required="mode == 'invoice_multi'"
                                    options="{'no_create': True, 'no_edit': True}"
                                    context="{'default_model': 'account.move'}"/>
                         </group>