How to disable "You have been assigned" email when a user creates a sales order in Odoo 10

In Odoo 10, when user "A" creates a new sales order and assigns it to a different salesperson (user "B"), no matter what configuration you have applied to email templates/subtypes/send notifications, an email is automatically sent to the customer and the salesperson (I am still amazed on which business logic was follow to send internal notification emails to customers by default).

The email is the well known one with this format:

"You have been assigned to SOxxxx."

To make things worse the email is set to "Auto-delete", so you do not even know what your system is sending to customers (no comments).

Which module or function or setting in Odoo 10 CE shall be overwritten to avoid such default behaviour?

Solution

Overwrite _message_auto_subscribe_notify method for sale.order class and add to context mail_auto_subscribe_no_notify.

from odoo import models, api


class SaleOrder(models.Model):
    _inherit = 'sale.order'

    @api.multi
    def _message_auto_subscribe_notify(self, partner_ids):
        """ Notify newly subscribed followers of the last posted message.
            :param partner_ids : the list of partner to add as needaction partner of the last message
                                 (This excludes the current partner)
        """
        return super(SaleOrder, self.with_context(mail_auto_subscribe_no_notify=True))\
                ._message_auto_subscribe_notify(partner_ids)

The original method will not send the message if that key is passed in the context

    @api.multi
    def _message_auto_subscribe_notify(self, partner_ids):
        """ Notify newly subscribed followers of the last posted message.
            :param partner_ids : the list of partner to add as needaction partner of the last message
                                 (This excludes the current partner)
        """
        if not partner_ids:
            return

        if self.env.context.get('mail_auto_subscribe_no_notify'):  # Here
            return

        # send the email only to the current record and not all the ids matching active_domain !
        # by default, send_mail for mass_mail use the active_domain instead of active_ids.
        if 'active_domain' in self.env.context:
            ctx = dict(self.env.context)
            ctx.pop('active_domain')
            self = self.with_context(ctx)

        for record in self:
            record.message_post_with_view(
                'mail.message_user_assigned',
                composition_mode='mass_mail',
                partner_ids=[(4, pid) for pid in partner_ids],
                auto_delete=True,
                auto_delete_message=True,
                parent_id=False, # override accidental context defaults
                subtype_id=self.env.ref('mail.mt_note').id)