[FIX] fields: do not set the inverse function on a readonly related field

This fixes #4681: prevent method copy() to write on the field.

openerp/addons/test_new_api/models.py

@@ -106,7 +106,7 @@ class Message(models.Model):
     display_name = fields.Char(string='Abstract', compute='_compute_display_name')
     size = fields.Integer(compute='_compute_size', search='_search_size')
     double_size = fields.Integer(compute='_compute_double_size')
-    discussion_name = fields.Char(related='discussion.name', readonly=True)
+    discussion_name = fields.Char(related='discussion.name')
 
     @api.one
     @api.constrains('author', 'discussion')

openerp/addons/test_new_api/tests/test_new_fields.py

@@ -294,7 +294,7 @@ class TestNewFields(common.TransactionCase):
         # by default related fields are not stored
         field = message._fields['discussion_name']
         self.assertFalse(field.store)
-        self.assertTrue(field.readonly)
+        self.assertFalse(field.readonly)
 
         # check value of related field
         self.assertEqual(message.discussion_name, discussion.name)

openerp/fields.py

@@ -460,7 +460,8 @@ class Field(object):
         # determine dependencies, compute, inverse, and search
         self.depends = ('.'.join(self.related),)
         self.compute = self._compute_related
-        self.inverse = self._inverse_related
+        if not (self.readonly or field.readonly):
+            self.inverse = self._inverse_related
         if field._description_searchable:
             # allow searching on self only if the related field is searchable
             self.search = self._search_related