Add constraint if account type is used on account.account

account_type_inactive/models/account_type.py

@@ -2,7 +2,8 @@
 # Copyright 2017 Camptocamp SA
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
 
-from odoo import models, fields
+from odoo import models, fields, api, _
+from odoo.exceptions import ValidationError
 
 
 class AccountAccountType(models.Model):
@@ -10,3 +11,13 @@ class AccountAccountType(models.Model):
     _inherit = 'account.account.type'
 
     active = fields.Boolean('Active', default=True)
+
+    @api.constrains('active')
+    def _check_account_moves(self):
+        if not self.active:
+            accounts = self.env['account.account'].search([
+                ('user_type_id', '=', self.id)])
+            if accounts:
+                raise ValidationError(_('You cannot inactive this account type'
+                                        ' as this type is is used on %d '
+                                        'accounts.' % len(accounts)))