Fine generator can generate overdue fines beyond max-fine amount (rounding error)

[Bill Erickson]

Evergreen 2.12 / affects all versions.

Seen in the wild:

1. Item is marked lost and $2.30 of overdue fines are voided.
2. Item is returned and a $2.30 "OVERDUES REINSTATED" billing is applied.
3. Additional $0.10 overdue fines are applied, totaling $3.10, with a max fine amount of $3.00.

In short, the fine generator should avoid use of int() for rounding:

% perl -e 'print int(100 * 2.30) . "\n"'
229

See also 'perldoc -f int'.

Simply removing the int() wrapper resolves the issue in a standalone test script. Note that we are using sprintf %.2f for creating new billings, so there is no danger of creating billings with meandering decimal values.

[Bill Erickson (berick)]

Noting for reference the int() issue has come up before with credit card payments: bug #1282751.

[Bill Erickson (berick)]

Branch with fix pushed:

http://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/berick/lp1704819-fine-gen-int-rounding

Confirmed total fines accumulated match pre-patch amounts on a concerto test system. Perl test pending.

[Jessica Woolford (jwoolford)]

We observed this behavior in our 2.12 system as well. We're running your patch. Thanks!

[Bill Erickson (berick)]

Re-marking as confirmed based on Jessica's comments.

[Bill Erickson (berick)]

We are also now running this patch in production.

[Galen Charlton (gmc)]

Pushed to master, rel_3_3, rel_3_2, and rel_3_1 on the strength of this having been run in production for a couple years and per discussion at http://irc.evergreen-ils.org/evergreen/2019-05-23#i_407072. Thanks, Bill!