_input-group.scss

// stylelint-disable selector-no-qualifying-type

//
// Base styles
//

.input-group {
  position: relative;
  display: flex;
  flex-wrap: wrap; // For form validation feedback
  align-items: stretch;
  width: 100%;

  > .form-control,
  > .form-select,
  > .form-file {
    position: relative; // For focus state's z-index
    flex: 1 1 0%;
    min-width: 0; // https://stackoverflow.com/questions/36247140/why-dont-flex-items-shrink-past-content-size
    margin-bottom: 0;

    + .form-control,
    + .form-select,
    + .form-file {
      margin-left: -$input-border-width;
    }
  }

  // Bring the "active" form control to the top of surrounding elements
  > .form-control:focus,
  > .form-select:focus,
  > .form-file .form-file-input:focus ~ .form-file-label {
    z-index: 3;
  }

  // Bring the custom file input above the label
  > .form-file .form-file-input:focus {
    z-index: 4;
  }

  > .form-control,
  > .form-select {
    &:not(:last-child) { @include border-right-radius(0); }
    &:not(:first-child) { @include border-left-radius(0); }
  }

  // Custom file inputs have more complex markup, thus requiring different
  // border-radius overrides.
  > .form-file {
    display: flex;
    align-items: center;

    &:not(:last-child) .form-file-label { @include border-right-radius(0); }
    &:not(:first-child) .form-file-label { @include border-left-radius(0); }
  }
}


// Prepend and append
//
// While it requires one extra layer of HTML for each, dedicated prepend and
// append elements allow us to 1) be less clever, 2) simplify our selectors, and
// 3) support HTML5 form validation.

.input-group-prepend,
.input-group-append {
  display: flex;

  // Ensure buttons are always above inputs for more visually pleasing borders.
  // This isn't needed for `.input-group-text` since it shares the same border-color