`invalid-feedback` should be inside `input-group`

[colinbm]

The style that triggers display of the error is (amongst others) .form-control.is-invalid ~ .invalid-feedback.

Currently the .invalid-feedback div is outside the .input-group and as .is-valid is set on the input itself, it's never displayed.

This has been addressed in twbs/bootstrap#25020

Added support for form validation feedback in input groups. .input-group now has flex-wrap: wrap; on by default, allowing you to place validation feedback within the .input-group and style it based on the input's overall state. This isn't applicable to file inputs though.

This means the .invalid-feedback should be located as the last item inside .input-group.

I will take a look at this myself and see if I can fix, but it's probably an easy fix for someone who knows the code better. Thanks if you get there first!

[lcreid]

A big thank you for taking the time to report this. And thanks for offering to take a look at a fix. I encourage you to have a go at submitting a PR. We really like to get first-time contributions. Post comments here if you need help and I'll try to give a hand. I'm pretty new to the code myself. Take a look at the CONTRIBUTING document if you haven't already.

As you know if you've read #361, we're in the middle of trying to prepare an official release of bootstrap_form for Bootstrap 4, so we're all pretty busy. And this is a completely community-supported gem. So your help would be really appreciated, but don't feel pressured if you can't.

[lcreid]

Fixing this would move me towards being able to finish #410 and #418, so I'll take a stab at a PR. Let me know if that's a bad thing.

[colinbm]

Go for it. I have got as far as writing a test for it, but my prospective fix seems... very wrong. (Regex replace after the html is generated)

[lcreid]

I'd love to get your test case, if you can push it to your fork and send me a link. Or even just cut and paste it into a comment here.

[colinbm]

Will do tomorrow. Away from computer at the moment.

[lcreid]

@colinbm take a look at PR #422, if you have a chance. Let me know what you think. I'll add your test case when I get it.

[colinbm]

@lcreid Looks good. You appear to have written the exact same test already! :)

colinbm@f035bf2