test_storage_web.py duplicates internal lease management logic

[exarkun]

test_storage_web.py contains:

    def backdate_lease(self, sf, renew_secret, new_expire_time):
        # ShareFile.renew_lease ignores attempts to back-date a lease (i.e.                                                                                                                   
        # "renew" a lease with a new_expire_time that is older than what the                                                                                                                  
        # current lease has), so we have to reach inside it.                                                                                                                                  
        for i,lease in enumerate(sf.get_leases()):
            if lease.renew_secret == renew_secret:
                lease = lease.renew(new_expire_time)
                f = open(sf.home, 'rb+')
                sf._write_lease_record(f, i, lease)
                f.close()
                return
        raise IndexError("unable to renew non-existent lease")

which is essentially a copy of the renew_lease function in immutable.py:

    def renew_lease(self, renew_secret, new_expire_time):
        for i,lease in enumerate(self.get_leases()):
            if timing_safe_compare(lease.renew_secret, renew_secret):
                # yup. See if we need to update the owner time.                                                                                                                               
                if new_expire_time > lease.get_expiration_time():
                    # yes                                                                                                                                                                     
                    lease = lease.renew(new_expire_time)
                    with open(self.home, 'rb+') as f:
                        self._write_lease_record(f, i, lease)
                return
        raise IndexError("unable to renew non-existent lease")

except it omits the "no going backwards" check and doesn't manage the lifetime of the open share file safely.

This duplication is undesirable for the usual reasons and can easily be avoided by having the real implementation allow for backdated leases on request.

[GitHub <noreply@…>]

In 7b554d1/trunk:

Merge pull request #1150 from tahoe-lafs/3832.backdated-leases

Supported backdated leases for the test suite

Fixes: ticket:3832