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["Stefan Rijnhart \(Therp\)" <915975@xxxxxxxxxxxxxxxxxx>]

** Changed in: therp-backports
       Status: Confirmed => Fix Released

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https://bugs.launchpad.net/bugs/915975

Title:
  Data corruption: fields.related writes to the target model with source
  id

Status in OpenERP Server:
  Confirmed
Status in Therp Backports:
  Fix Released

Bug description:
  Hi,

  Problem:
  ------------
  A fields.related with type='many2many' tries to write to the target model but with id of the source model in case the original value of the many2many field on the target resource is empty.

  Analysis:
  -----------
  Take for example a column definition in osv class 'source.model':

    'related_field_id': fields.related('target_model_id',
  'target_field', type='many2many'),

  A value is written to this field. The current value on the target
  model is empty.

  The method related._fnct_write()[1] from osv/fields.py loops over
  ('target_model_id', 'target_field'). The second iteration is supposed
  to retrieve the resource id of the target model. It does so by setting
  't_id' to t_data['id'] in three different places (!) in the loop,
  where 't_data' is the browse object of the target resource. It still
  fails to do so in the circumstances described above.

  Although the code is a bit difficult to read, you can check that *if*
  the current value of the field (t_data[self.arg[i]])[2] is empty *and*
  type is in ('one2many', 'many2one')[3], t_id does not get set to
  t_data['id'] but keeps its original value instead. This original value
  is the resource id of the source model set in the first iteration of
  the loop.

  Result:
  ---------
  If a resource exists with this id, the new value get silently written to this wrong resource. If such a resource does not exist, the following error occurs: "'One of the records you are trying to modify has already been deleted".

  This problem occurs on openerp-server/6.0 (rev. 3565). Trunk has not
  been tested, but the function in which the problem occurs has remained
  unchanged.

  [1] http://bazaar.launchpad.net/~openerp/openobject-server/6.0/view/head:/bin/osv/fields.py?start_revid=3566#L863
  [2] http://bazaar.launchpad.net/~openerp/openobject-server/6.0/view/head:/bin/osv/fields.py?start_revid=3566#L874
  [3] http://bazaar.launchpad.net/~openerp/openobject-server/6.0/view/head:/bin/osv/fields.py?start_revid=3566#L875

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