[FIX] core: first onchange on new one2many line

Consider models `M` and `L`, with a one2many field `M.l_ids` with
inverse `L.m_id`.  Consider also a computed field `L.foo` that depends
on `L.m_id`.

The field `L.foo` is not computed correctly by `onchange` on a new line
in the form view of `M`: its value is forced to `False` because it has
no default, and is not recomputed by `onchange` since the field `L.m_id`
is never triggered an `onchange`.

Modify the method `onchange` to not force fields without a default to
`False`, and return all fields.

1 files changed, 13 insertions, 0 deletions

diff --git a/odoo/addons/test_new_api/tests/test_onchange.py b/odoo/addons/test_new_api/tests/test_onchange.py
index 5bffeae5f86..38c7b8be531 100644
--- a/odoo/addons/test_new_api/tests/test_onchange.py
+++ b/odoo/addons/test_new_api/tests/test_onchange.py
@@ -378,6 +378,19 @@ class TestOnChange(SavepointCaseWithUserDemo):
         result = Foo.onchange(values, 'value1', field_onchange)
         self.assertEqual(result['value'], {})
 
+    def test_onchange_one2many_first(self):
+        partner = self.env['res.partner'].create({
+            'name': 'X',
+            'country_id': self.env.ref('base.be').id,
+        })
+        with common.Form(self.env['test_new_api.multi']) as form:
+            form.partner = partner
+            self.assertEqual(form.partner, partner)
+            self.assertEqual(form.name, partner.name)
+            with form.lines.new() as line:
+                # the first onchange() must have computed partner
+                self.assertEqual(line.partner, partner)
+
     def test_onchange_one2many_value(self):
         """ test the value of the one2many field inside the onchange """
         discussion = self.env.ref('test_new_api.discussion_0')