Comment 11 for bug 1155606

Hello:

For Storno accounting Tax/Base amount is always == (debit + credit)
           Still trying to find the case where it is not.
           Maybe for contra check is abs(tax_amount) = abs(debit + credit) ???

As extreme measure I'am using trigger on some databases:
"""
        cr.execute('''
                CREATE OR REPLACE FUNCTION debit_credit2tax_amount() RETURNS trigger AS
                $debit_credit2tax_amount$
                BEGIN
                   NEW.tax_amount := CASE when NEW.tax_code_id is not null
                                           then coalesce(NEW.credit, 0.00)+coalesce(NEW.debit, 0.00)
                                           else 0.00
                                      END;
                   RETURN NEW;
                END;
                $debit_credit2tax_amount$ LANGUAGE plpgsql;

                ALTER FUNCTION debit_credit2tax_amount() OWNER TO %s;

                DROP TRIGGER IF EXISTS move_line_tax_amount ON account_move_line;
                CREATE TRIGGER move_line_tax_amount BEFORE INSERT OR UPDATE ON account_move_line
                    FOR EACH ROW EXECUTE PROCEDURE debit_credit2tax_amount();
        '''%(tools.config['db_user'],))

"""

From account_storno module :

class account_move_line(osv.osv):
    _inherit = "account.move.line"
    #Original constraints
    #_sql_constraints = [
    #('credit_debit1', 'CHECK (credit*debit=0)', 'Wrong credit or debit value in accounting entry !'),
    #('credit_debit2', 'CHECK (credit+debit>=0)', 'Wrong credit or debit value in accounting entry !'),
    #]

    # credit_debit1 is valid constraint. Clear message
    # credit_debit2 is replaced with dummy constraint that is always true.

    _sql_constraints = [
        ('credit_debit1', 'CHECK (credit*debit=0)', 'Wrong credit or debit value in accounting entry! Either credit or debit must be 0.00.'),
        ('credit_debit2', 'CHECK (abs(credit+debit)>=0)', 'Wrong credit or debit value in accounting entry !'),
    ]

    def _check_contra_minus(self, cr, uid, ids, context=None):
        """ This is to restore credit_debit2 check functionality, for contra journals
        """
        for l in self.browse(cr, uid, ids, context=context):
            if l.journal_id.posting_policy == 'contra':
                if not (l.debit * l.credit) >= 0.0:
                    return False
        return True

    def _check_storno_tax(self, cr, uid, ids, context=None):
        """For Storno accounting Tax/Base amount is always == (debit + credit)
           Still trying to find the case where it is not.
           Maybe for contra check is abs(tax_amount) = abs(debit + credit) ???
        """
        for l in self.browse(cr, uid, ids, context=context):
            if l.journal_id.posting_policy == 'storno' and l.tax_code_id:
                if float_compare((l.debit + l.credit), l.tax_amount, precision_digits = 2) != 0: #precision_digits=dp.get_precision('Account')[1])
                    return False
        return True

    _constraints = [
        (_check_contra_minus, _('Negative credit or debit amount is not allowed for "contra" journal policy.'), ['journal_id']),
        (_check_storno_tax, _('Invalid tax amount. Tax amount can be 0.00 or equal to (Credit + Debit).'), ['journal_id']),
    ]