feat(custom-range): Add support for input-group and validation

Currently the .custom-range input does not support validation styling, nor is .custom-range supported inside .input-groups.

I suggest CSS similar to the following to handle both input-groups and validation

Basic validation:

.custom-range {
  border: 1px solid transparent;
  border-radius: .25rem;
}
/* leave above out to not have the non .input-group ranges
 * bordered when invalid or valid
 */

.custom-range.is-invalid,
.was-validated .custom-range:invalid {
  border-color: #dc3545;
}
.custom-range.is-invalid:focus,
.was-validated .custom-range:invalid:focus {
  border-color: #dc3545;
  box-shadow: 0 0 0 .2rem rgba(220,53,69,.25);
}
.custom-range.is-valid,
.was-validated .custom-range:valid {
  border-color: #28a745;
}
.custom-range.is-valid:focus,
.was-validated .custom-range:valid:focus {
  border-color: #28a745;
  box-shadow: 0 0 0 .2rem rgba(40,167,69,.25);
}

Input groups:

.input-group > .custom-range {
  display: block;
  height: calc(2.25rem + 2px);
  padding: 0 .75rem;
  font-size: 1rem;
  line-height: 1.5;
  background-clip: padding-box;
  border: 1px solid #ced4da;
  border-radius: .25rem;
  transition: border-color .15s ease-in-out, box-shadow .15s ease-in-out;
}
.input-group > .custom-range {
  position: relative;
  -ms-flex: 1 1 auto;
  flex: 1 1 auto;
  width: 1%;
  margin-bottom: 0;
}
.input-group > .custom-range:focus {
  z-index: 3;
}
.input-group-sm > .custom-range {
  height: calc(1.8125rem + 2px);
  padding: 0 .5rem;
  font-size: .875rem;
  line-height: 1.5;
  border-radius: .2rem;
}
.input-group-lg > .custom-range {
  height: calc(2.875rem + 2px);
  padding-left: 0 1rem;
  font-size: 1.25rem;
  line-height: 1.5;
  border-radius: .3rem;
}
.input-group > .custom-range:not(:last-child) {
  border-top-right-radius: 0;
  border-bottom-right-radius: 0;
}
.input-group > .custom-range:not(:first-child) {
  border-top-left-radius: 0;
  border-bottom-left-radius: 0;
}

/* Style for focusing custom-range when inside an .input-group.
 * Normally only the range thumb has focus styling, but this keeps
 * input-group inputs looking consistent during validation
 */
.input-group .custom-range:focus {
    background-color: #fff;
    border-color: #80bdff;
    outline: 0;
    box-shadow: 0 0 0 .2rem rgba(0,123,255,.25);
}

Results:

An alternative to using the borders of .custom-range that is not inside an .input-group, would be to change the background color of the track (maybe use the .alert-danger and .alert-success background or border colors), and to color the range handle to match validation.

[ysds]

I understood about a scenario with server side validation. But I feel strange about the border around a slider control. I prefer without borders style.

https://codepen.io/anon/pen/OBKGKY

[mdo]

I’m a no on the input group—input groups were always designed for textual inputs first and foremost. In general I don’t see much usage of range inputs already, and putting them inside an input group feels premature at this point. I like the min/max demo, but not enough to see it added 😃.