[IMP] base: warning on decimal precision change

odoo/addons/base/models/decimal_precision.py

@@ -1,7 +1,7 @@
 # -*- encoding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
-from odoo import api, fields, models, tools
+from odoo import api, fields, models, tools, _
 import odoo.addons
 
 import logging
@@ -49,6 +49,23 @@ class DecimalPrecision(models.Model):
         self.clear_caches()
         return res
 
+    @api.onchange('digits')
+    def _onchange_digits_warning(self):
+        if self.digits < self._origin.digits:
+            return {
+                'warning': {
+                    'title': _("Warning for %s", self.name),
+                    'message': _(
+                        "The precision has been reduced for %s.\n"
+                        "Note that existing data WON'T be updated by this change.\n\n"
+                        "As decimal precisions impact the whole system, this may cause critical issues.\n"
+                        "E.g. reducing the precision could disturb your financial balance.\n\n"
+                        "Therefore, changing decimal precisions in a running database is not recommended.",
+                        self.name,
+                    )
+                }
+            }
+
 # compatibility for decimal_precision.get_precision(): expose the module in addons namespace
 dp = sys.modules['odoo.addons.base.models.decimal_precision']
 odoo.addons.decimal_precision = dp