[FIX] mail: add all attachments at template onchange

Fine-tuning of 516f22c3987.
This commit missed attachments that are linked to a mail.template,
which should be added to every mail sent using the template.

To make sure that we both fix the duplicates and the generation issue,
we add a test.

opw 2000515
opw 1998782

closes odoo/odoo#33653

Signed-off-by: Nans Lefebvre (len) <len@odoo.com>

2 files changed, 41 insertions, 0 deletions

diff --git a/addons/mail/wizard/mail_compose_message.py b/addons/mail/wizard/mail_compose_message.py
index dcaf346e139..913ca46bce9 100644
--- a/addons/mail/wizard/mail_compose_message.py
+++ b/addons/mail/wizard/mail_compose_message.py
@@ -414,6 +414,7 @@ class MailComposer(models.TransientModel):
         # ORM handle the assignation of command list on new onchange (api.v8),
         # this force the complete replacement of x2many field with
         # command and is compatible with onchange api.v7
+        attachment_ids += values.pop('attachment_ids' , [])
         values = self._convert_to_write(values)
         if attachment_ids:
             values.update(attachment_ids=[(6, 0, attachment_ids)])
diff --git a/addons/test_mail/tests/test_mail_template.py b/addons/test_mail/tests/test_mail_template.py
index e1b14d57a20..4258fff577b 100644
--- a/addons/test_mail/tests/test_mail_template.py
+++ b/addons/test_mail/tests/test_mail_template.py
@@ -236,3 +236,43 @@ class TestMailTemplate(BaseFunctionalTest, MockEmails, TestRecipients):
         new_partner = Partner.search([('email', '=', email_new_partner)])
         self.assertTrue(new_partner)
         self.assertEqual(new_partner.company_id, company1)
+
+    def test_composer_template_onchange_attachments(self):
+        """Tests that all attachments are added to the composer,
+        static attachments are not duplicated and while reports are re-generated,
+        and that intermediary attachments are dropped."""
+
+        composer = self.env['mail.compose.message'].create({})
+        report_template = self.env.ref('web.action_report_externalpreview')
+        template_1 = self.email_template.copy({
+            'report_template': report_template.id,
+        })
+        template_2 = self.email_template.copy({
+            'attachment_ids': False,
+            'report_template': report_template.id,
+        })
+
+        onchange_templates = [template_1, template_2, template_1]
+        attachments_onchange = []
+        # template_1 has two static attachments and one dynamically generated report,
+        # template_2 only has the report, so we should get 3, 1, 3 attachments
+        attachment_numbers = [3, 1, 3]
+
+        for template in onchange_templates:
+            onchange = composer.onchange_template_id(
+                template.id, 'comment', 'mail.test', self.test_record.id
+            )
+            values = composer._convert_to_record(composer._convert_to_cache(onchange['value']))
+            attachments = values['attachment_ids']
+            composer.attachment_ids = attachments  # we apply the onchange
+            attachments_onchange.append(attachments)
+
+        self.assertEqual(
+            [len(attachments) for attachments in attachments_onchange],
+            attachment_numbers,
+        )
+
+        self.assertTrue(
+            len(attachments_onchange[0] & attachments_onchange[2]) == 2,
+            "The two static attachments on the template should be common to the two onchanges"
+        )