[FIX] base: prevent json decoder error for default values

JSONDecoderError occurs when users enters invalid JSON format data in
'Default Value' field inside 'User-defined Defaults' and wherever this field is
being accessed to get default value this traceback will be generated.

Steps to reproduce:
1) Install 'Contacts' module.
2) Open 'Settings' > 'Technical' > 'User-defined Defaults'.
3) Click on record 'Language' > 'EDIT' button > in 'Default Value' field enter
   any improper JSON format data (e.g 'Maa' : FI ) .
4) Now, open 'Contacts' module > click on 'CREATE' button and traceback would be
   generated.

By applying this, it will check for proper JSON format.

Sentry-4169062951

closes odoo/odoo#126239

X-original-commit: 0e6e322d
Signed-off-by: Rémy Voet (ryv) <ryv@odoo.com>

odoo/addons/base/i18n/base.pot

@@ -13002,7 +13002,12 @@ msgid "Invalid 'group by' parameter"
 msgstr ""
 #. module: base
-#. odoo-python
+#: code:addons/base/models/ir_default.py:0
+#, python-format
+msgid "Invalid JSON format in Default Value field."
+msgstr ""
+
+#. module: base
 #: code:addons/models.py:0
 #, python-format
 msgid "Invalid aggregation function %r."

odoo/addons/base/models/ir_default.py

@@ -22,6 +22,14 @@ class IrDefault(models.Model):
     condition = fields.Char('Condition', help="If set, applies the default upon condition.")
     json_value = fields.Char('Default Value (JSON format)', required=True)
 
+    @api.constrains('json_value')
+    def _check_json_format(self):
+        for record in self:
+            try:
+                json.loads(record.json_value)
+            except json.JSONDecodeError:
+                raise ValidationError(_('Invalid JSON format in Default Value field.'))
+
     @api.model_create_multi
     def create(self, vals_list):
         self.clear_caches()

odoo/addons/base/tests/test_ir_default.py

@@ -143,3 +143,13 @@ class TestIrDefault(TransactionCase):
             IrDefault.with_context(allowed_company_ids=company_b_a.ids).get_model_defaults('res.partner')['ref'],
             'CBDefault',
         )
+
+    def test_json_format_invalid(self):
+        """ check the _check_json_format constraint """
+        IrDefault = self.env['ir.default']
+        field_id = self.env['ir.model.fields'].search([('model', '=', 'res.partner'), ('name', '=', 'ref')])
+        with self.assertRaises(ValidationError):
+            IrDefault.create({
+                'field_id': field_id.id,
+                'json_value': '{"name":"John", }',
+            })