[FIX] models: in onchange, false changes where detected in many2many …

…fields

This was due to secondary fields loaded from database in 'onchange' mode.  In
that mode, the secondary fields were marked 'dirty', and therefore returned by
the method `onchange`.  The fix consists in loading those secondary fields in
cache before processing the onchanges.

This incidentally fixes a test on method `onchange`: in a one2many field, some
dirty fields were unexpectedly returned in the result.  This was due to those
fields being loaded while processing onchanges.

openerp/addons/test_new_api/tests/test_onchange.py

@@ -146,8 +146,6 @@ def test_onchange_one2many(self):
             }),
             (1, message.id, {
                 'name': "[%s] %s" % ("Foo", USER.name),
-                # Note: size is computed because it was not provided beforehand
-                'size': len(BODY),
             }),
         ])
 

openerp/models.py

@@ -5787,6 +5787,11 @@ def onchange(self, values, field_name, field_onchange):
             # attach `self` with a different context (for cache consistency)
             record._origin = self.with_context(__onchange=True)
 
+        # load fields on secondary records, to avoid false changes
+        with env.do_in_onchange():
+            for field_seq in secondary:
+                record.mapped(field_seq)
+
         # determine which field(s) should be triggered an onchange
         todo = list(names) or list(values)
         done = set()