Impacted versions:
10.0 + e

Steps to reproduce:
1) Create a salary rule that has 'appears_on_payslip' = False.
- An example would be a company contribution that the employee does not need to see.
  2) Add it to a salary structure
  3) run a payroll/payslip calculation

Current behavior:
Numerous thing.
1) Every time you compute sheet, you will duplicate these 'hidden' lines
2) details_by_salary_rule_category no longer has any of the hidden lines, though they certainly contribute to categories (e.g. tests will fail, and bad things)
3) when using hr_payroll_account, lines with contribution registers and accounts that SHOULD be on the journal entry are not !!

Expected behavior:
1) every time you compute the sheet, the lines should be deleted and recalculated
2) details_by_salary_rule_category should have all categories (to be able to make complex rules and tests)
3) journal entry should have a line for every line with an account

Pull Request eminent.

"""a class that will be used into the , mainly for usability purposes"""
            def sum(self, code, from_date, to_date=None):
                if to_date is None:
                    to_date = fields.Date.today()
                self.env.cr.execute("""
                    SELECT sum(amount) as sum
                    FROM hr_payslip as hp, hr_payslip_input as pi
                    WHERE hp.employee_id = %s AND hp.state = 'done'
                    AND hp.date_from >= %s AND hp.date_to <= %s AND hp.id = pi.payslip_id AND pi.code = %s""",
                    (self.employee_id, from_date, to_date, code))
                return self.env.cr.fetchone()[0] or 0.0
        class WorkedDays(BrowsableObject):
            """a class that will be used into the , mainly for usability purposes"""
            def _sum(self, code, from_date, to_date=None):
                if to_date is None:
                    to_date = fields.Date.today()
                self.env.cr.execute("""
                    SELECT sum(number_of_days) as number_of_days, sum(number_of_hours) as number_of_hours
                    FROM hr_payslip as hp, hr_payslip_worked_days as pi
                    WHERE hp.employee_id = %s AND hp.state = 'done'
                    AND hp.date_from >= %s AND hp.date_to <= %s AND hp.id = pi.payslip_id AND pi.code = %s""",
                    (self.employee_id, from_date, to_date, code))
                return self.env.cr.fetchone()
            def sum(self, code, from_date, to_date=None):
                res = self._sum(code, from_date, to_date)
                return res and res[0] or 0.0
            def sum_hours(self, code, from_date, to_date=None):
                res = self._sum(code, from_date, to_date)
                return res and res[1] or 0.0
        class Payslips(BrowsableObject):