[v4 beta-3] [bug] Input group button loses border radius if group has invalid feedback

[martinbean]

I have an input group with a single text input, and a button as a suffix. If I add a class of .is-invalid to the input, and add an .invalid-feedback element to the group, the button suffix loses its border-radius because it’s no longer the last child within the group.

Mark-up:

<div class="input-group">
    <input type="text" name="coupon" id="coupon" class="form-control is-invalid" autofocus required />
    <div class="input-group-append">
        <button type="submit" class="btn btn-primary">Apply coupon</button>
    </div>
    <div class="invalid-feedback">You have already redeemed this coupon.</div>
</div>

Screen-shot:

[mdo]

Duplicate of #25110. I'm getting closer with #25352, but might need an extra class to provide all the functionality we want :(.

[martinbean]

@mdo Ah! I did search Issues first to see if it had already been reported, but missed that one. Sorry!