[IMP] - manage substitution for mail.thread message_post_with_template

report_substitute/wizards/__init__.py

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+from . import mail_compose_message

report_substitute/wizards/mail_compose_message.py

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+# Copyright 2019 ACSONE SA/NV
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+
+from odoo import api, models
+
+
+class MailComposeMessage(models.TransientModel):
+
+    _inherit = 'mail.compose.message'
+
+    @api.multi
+    @api.onchange('template_id')
+    def onchange_template_id_wrapper(self):
+        old_report_template = False
+        if (
+            self.template_id
+            and self.template_id.report_template
+            and self.env.context.get('active_ids')
+        ):
+            active_ids = self.env.context.get('active_ids')
+            old_report_template = self.template_id.report_template
+            self.template_id.report_template = (
+                old_report_template.get_substitution_report(active_ids)
+            )
+        res = super().onchange_template_id_wrapper()
+        if old_report_template:
+            self.template_id.report_template = old_report_template
+        return res