Add purchase buyer module

purchase_order_buyer/models/purchase_order.py

@@ -0,0 +1,28 @@
+# -*- coding: utf-8 -*-
+# Copyright 2018 Raphael Reverdy https://akretion.com
+# License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl.html).
+
+from odoo import api, fields, models
+
+
+class PurchaseOrder(models.Model):
+    _inherit = 'purchase.order'
+
+    user_id = fields.Many2one(
+        'res.users',
+        string='Buyer', index=True,
+        track_visibility='onchange',
+        default=lambda self: self.env.user)
+
+    @api.multi
+    @api.onchange('partner_id')
+    def onchange_partner_id(self):
+        """Update the user_id (buyer)"""
+        for rec in self:
+            if rec.partner_id and rec.partner_id.user_id:
+                user_id = rec.partner_id.user_id.id
+            else:
+                user_id = self.env.user
+            return rec.update({
+                'user_id': user_id,
+            })