Add test to check that depends on _parent_ contains also the relation

Otherwise, the depends decorator will set the relation to None if the record
is not in One2Many widget. And the method will not behave the same as if the
record was in a One2Many widget.
And if it is an on_change call, it will remove the value on the client side.

issue7249
review45291002

trytond/tests/test_tryton.py

@@ -315,6 +315,27 @@ class ModuleTestCase(unittest.TestCase):
                         'Unknown depends %s in button "%s"."%s"' % (
                             list(depends - set(model._fields)), mname, bname))
 
+    @with_transaction()
+    def test_depends_parent(self):
+        "Test depends on _parent_ contains also the parent relation"
+        for mname, model in Pool().iterobject():
+            if not isregisteredby(model, self.module):
+                continue
+            for fname, field in model._fields.iteritems():
+                for attribute in ['depends', 'on_change', 'on_change_with',
+                        'selection_change_with', 'autocomplete']:
+                    depends = getattr(field, attribute, [])
+                    for depend in depends:
+                        prefix = []
+                        for d in depend.split('.'):
+                            if d.startswith('_parent_'):
+                                relation = '.'.join(
+                                    prefix + [d[len('_parent_'):]])
+                                assert relation in depends, (
+                                    'Missing "%s" in "%s"."%s"."%s"' % (
+                                        relation, mname, fname, attribute))
+                            prefix.append(d)
+
     @with_transaction()
     def test_field_methods(self):
         'Test field methods'