def _compute_fixture_value(fixturedef, session):
    """ Computes the fixturedef evaluated in the scope of the first item in the
    list of collected items. """
    request = session.items[0]._request
    request._compute_fixture_value(fixturedef)
    res = fixturedef.cached_result[0]
    request._fixture_defs[fixturedef.argname] = fixturedef
    return res
