Fix confusing crash when an unknown filter name is passed to optional/required

[hikmetba-bit]

Summary

Fixes #2129.

Mojolicious::Validator::Validation::optional() (and required(), which calls it) mapped the list of filter names straight to callbacks before calling each one:

for my $cb (map { $self->validator->filters->{$_} } @filters) {
  @input = map { $self->$cb($name, $_) } @input;
}

If a filter name is unknown (typo, or the filter was never registered), $self->validator->filters->{$_} is undef, and $self->$cb(...) then crashes with:

Use of uninitialized value $cb in method lookup at .../Validation.pm line 74.
Can't locate object method "" via package "Mojolicious::Validator::Validation"

— which gives no indication of which filter name was actually the problem, as the original reporter found while debugging a typo'd filter in production.

Fix

The loop now walks the filter names directly and croaks with a clear message naming the offending filter as soon as it finds one with no matching entry, before ever attempting the method call:

for my $filter (@filters) {
  my $cb = $self->validator->filters->{$filter};
  Carp::croak qq{Unknown filter "$filter"} unless defined $cb;
  @input = map { $self->$cb($name, $_) } @input;
}

Carp was already imported (use Carp ();) and this same Carp::croak pattern is already used elsewhere in the same file (BUILD_DYNAMIC), so this stays consistent with the existing code style.

Added a Changes entry and a regression test in t/mojolicious/validation_lite_app.t (Unknown filter subtest) asserting the new, clear error message.

Verification

This environment's Perl install could not load Mojolicious itself — core modules it depends on transitively (Pod::Usage, and something in File::Spec resolution) are broken/missing in this particular install, so I could not run the real test suite (prove -l t/mojolicious/validation_lite_app.t) here.

To still verify the actual logic change (not just eyeball it), I ported just the affected loop — old and new versions — into a standalone script using only Carp and Test::More (both of which do load correctly here), and confirmed:

1. The old logic really does crash with the exact confusing Can't locate object method "" via package ... message on an unknown filter name.
2. The new logic croaks with the clear Unknown filter "<name>" message instead.
3. The new logic is unchanged for a known filter (no regression).
4. The new logic is unchanged when no filters are passed at all (the common case).

All four checks passed. I could not run the actual t/mojolicious/validation_lite_app.t file I added the regression test to, or the wider suite, in this environment — please have CI/a reviewer confirm it passes before merge.

Test plan

• CI: prove -l t/mojolicious/validation_lite_app.t passes, including the new "Unknown filter" subtest
• CI: full test suite shows no regressions
• Manual: reproduce the original crash on main, confirm this branch instead raises a clear Unknown filter "..." error

🤖 Generated with Claude Code

[kraih]

Afraid we do not accept PRs with a Co-Authored-By an AI agent. You may of course use AI assistants, but a human has to take full responsibility for the patch.