Include the depends of the getter function when depending on a Function field

Since c47b3642f1a6, the getter of a Function field may be called if there is no
value set for it on the instance.
In the on_change context, this may set the missing fields to None if they were
not defined in the depends of the method called. In addition to compute a wrong
value, those fields are then returned as modified.

Closes #13735

trytond/trytond/model/modelview.py

@@ -150,6 +150,17 @@ class ModelView(Model):
 
             meth_names = list(methods['depend_methods'][function_name])
             meth_done = set()
+
+            for depend in getattr(field, attribute):
+                if '.' in depend:
+                    depend, _ = depend.split('.', 1)
+                if depend.startswith('_parent_'):
+                    depend = depend[len('_parent_'):]
+                if dep_field := getattr(cls, depend, None):
+                    if (isinstance(dep_field, fields.Function)
+                            and dep_field.getter.startswith('on_change_with')):
+                        meth_names.append(dep_field.getter)
+
             while meth_names:
                 meth_name = meth_names.pop()
                 method = getattr(cls, meth_name)

trytond/trytond/tests/test_field_depends.py

@@ -263,3 +263,26 @@ class FieldDependsTestCase(TestCase):
                 ]:
             with self.subTest(value=value):
                 self.assertEqual(fields.get_eval_fields(value), result)
+
+    def test_depends_function_getter(self):
+        "Tests depends on Function field with on_change_with getter"
+
+        class Model(ModelView):
+            __name__ = 'test.modelview.function_getter_depends'
+
+            test = fields.Char("Test")
+            foo = fields.Function(fields.Char("Foo"), 'on_change_with_foo')
+            bar = fields.Char("Bar")
+
+            @fields.depends('foo')
+            def on_change_test(self):
+                pass
+
+            @fields.depends('bar')
+            def on_change_with_foo(self, name=None):
+                pass
+
+        Model.__setup__()
+        Model.__post_setup__()
+
+        self.assertEqual(Model.test.on_change, {'foo', 'bar'})