Form::PATTERN doesn't allow for case-insensitive checks

[renekliment]

Version: 2.4.x

Bug Description

Hi! I'm trying to perform a case-insensitive pattern validation using the Form::PATTERN form rule, but it seems the functionality isn't there.

1. Both the PHP & JS code puts stuff before and after the regexp so using global modifiers is not possible. Moreover, JS doesn't support in-line regexp modifiers.
2. It seems that Form::REGEXP used to exist in the past (but was removed) that could do this. Also, in netteForms.js, the handler function is still there.

Steps To Reproduce

$control->addRule(Form::PATTERN, 'Invalid file extension.', "(.*)\.(txt|md)");

Expected Behavior

To be able to use the i modifier. Or to be able to achieve the same behavior in a reasonable way.

Possible Solution

Not sure. I don't know the reason behind removing Form::REGEXP and it seems weird to me that people wouldn't want to use this. Do they write new validation rules instead?

[dg]

It should be compatible with HTML5 attribute pattern

[renekliment]

@dg I see, makes sense. What was the reason for removing Form::REGEXP then? Duplicity? If that's the case and the only reason, I believe it would be beneficial to bring it back, because it provides an added value. I can open a PR if it makes sense.

[dg]

Yes, duplicity.

Because REGEXP had a little different syntax, it might be better to add new PATTERN_ICASE (or similar name).

[renekliment]

@dg Okay, I'll try to cook up a PR. Thank you.