ant-design/style/mixins/input.less

.ant-input(){
  position: relative;
  display: inline-block;
  margin: 0 0;
  padding: 4px 10px;
  border-radius: 6px 6px;
  border: 1px solid #d9d9d9;
  background-color: #ffffff;
  color: #666;
  line-height: 1.5;
  -webkit-transform: border 0.3s cubic-bezier(0.35, 0, 0.25, 1), background 0.3s cubic-bezier(0.35, 0, 0.25, 1), box-shadow 0.3s cubic-bezier(0.35, 0, 0.25, 1);
  transform: border 0.3s cubic-bezier(0.35, 0, 0.25, 1), background 0.3s cubic-bezier(0.35, 0, 0.25, 1), box-shadow 0.3s cubic-bezier(0.35, 0, 0.25, 1);
  .transition(all .3s @ease-in-out);

  &:hover {
    border-color: #23c0fa;
  }

  &:focus {
    border-color: #23c0fa;
    box-shadow: 0 0 3px #23c0fa;
  }
}

// common mixins for input
.input-lg() {
  padding: @input-padding-lg;
  font-size: @input-font-size-lg;
}

.input-sm() {
  padding: @input-padding-vertical-sm @input-padding-horizontal;
  font-size: @input-font-size-sm;
}

// Basic style for input
.input() {
  position: relative;
  display: block;
  padding: @input-padding-vertical-base @input-padding-horizontal;
  width: 100%;
  font-size: @input-font-size;
  line-height: @line-height-base;
  color: @input-color;
  background-color: @input-bg;
  background-image: none;
  border: 1px solid @input-border-color;
  border-radius: @input-border-radius;
  // Reset placeholder
  .placeholder();
  .transition(~"border @{duration-300} @{ease-in-out}, background @{duration-300} @{ease-in-out}, box-shadow @{duration-300} @{ease-in-out}");

  &:hover {
    border-color: @input-hover-border-color;
  }

  &:focus {
    @color-rgba: rgba(red(@input-focus-border-color), green(@input-focus-border-color), blue(@input-focus-border-color), .8);
    border-color: @input-focus-border-color;
    outline: 0;
    box-shadow: 0 0 3px @color-rgba;
  }

  &[disabled],
  &[readonly],
  fieldset[disabled] & {
    background-color: @input-disabled-bg;
    opacity: 1; 
    &:hover {
      border-color: @input-border-color;
    }
  }

  &[disabled],
  fieldset[disabled] & {
    cursor: @cursor-disabled;
  }

  // Reset height for `textarea`s
  textarea& {
    height: auto;
  }

  // Size
  &-lg {
    .input-lg();
  }

  &-sm {
    .input-sm();
  }
}

// Input with icons, you can define @height if you wish to change the input size
.input-with-icon(@height: @input-height-base) {
  position: relative;

  .@{iconfont-css-prefix} {
    position: absolute;
    bottom: 0;
    right: 0;
    z-index: 2;
    .square(@height);
    font-size: 14px;
    line-height: @height;
    text-align: center;
    pointer-events: none;
  }
}

// Input-group
.input-group(@inputClass) {
  // define the button style for input-group
  @inputBtn: input-btn;

  position: relative;
  display: table;
  border-collapse: separate;

  // Undo padding and float of grid classes
  &[class*="col-"] {
    float: none;
    padding-left: 0;
    padding-right: 0;
  }

  &-addon,
  &-btn,
  &-btn-vertical,
  .@{inputClass} {
    display: table-cell;

    &:not(:first-child):not(:last-child) {
      border-radius: 0;
    }
  }

  &-addon,
  &-btn,
  &-btn-vertical {
    width: 1%;
    white-space: nowrap;
    vertical-align: middle;
  }

  .@{inputClass} {
    position: relative;
    z-index: 2;
    float: left;
    width: 100%;
    margin-bottom: 0;
  }

  &-addon {
    padding: @input-padding-vertical-base @input-padding-horizontal;
    font-size: @font-size-base;
    font-weight: normal;
    line-height: 1;
    color: @input-color;
    text-align: center;
    background-color: #eee;
    border: 1px solid @input-border-color;
    border-radius: @input-border-radius;

    input[type="radio"],
    input[type="checkbox"] {
      margin-top: 0;
    }
  }

  .@{inputBtn} {
    .btn();
    .button-size(@input-padding-vertical-base @input-padding-horizontal; @font-size-base; @input-border-radius);
    .button-variant(@input-color; #eee; @input-border-color);

    .@{iconfont-css-prefix} {
      line-height: 1;
      margin-left: 8px;
    }
  }

  &-btn {
    position: relative;
  
    > .@{inputBtn} {
      position: relative;
      + .@{inputBtn} {
        margin-left: -1px;
      }
    }

    // Negative margin to only have a 1px border between the two
    &:first-child {
      > .@{inputBtn} {
        margin-right: -1px;
      }
    }
    &:last-child {
      > .@{inputBtn} {
        margin-left: -1px;
      }
    }
  }

  &-btn-vertical {
    position: relative;
    > .@{inputBtn} {
      display: block;
      float: none;
      width: 22px;
      height: 14px;
      margin-left: -1px;
      border-radius: 0;

      &:first-child {
        border-top-right-radius: 6px;
      }

      &:last-child {
        margin-top: -1px;
        height: 15px;
        border-bottom-right-radius: 6px;
      }
    }

    .@{iconfont-css-prefix} {
      position: absolute;
      top: 0;
      left: 4px;
      margin: 0!important;
      font-size: 12px!important;
    }
  }

  // Reset rounded corners
  .@{inputClass}:first-child,
  &-addon:first-child,
  &-btn:first-child > .@{inputBtn},
  &-btn:last-child > .@{inputBtn}:not(:last-child):not(.dropdown-toggle) {
    border-bottom-right-radius: 0;
    border-top-right-radius: 0;
  }
  
  &-addon:first-child {
    border-right: 0;
  }
  
  .@{inputClass}:last-child,
  &-addon:last-child,
  &-btn:last-child > .@{inputBtn},
  &-btn:first-child > .@{inputBtn}:not(:first-child) {
    border-bottom-left-radius: 0;
    border-top-left-radius: 0;
  }
  
  &-addon:last-child {
    border-left: 0;
  }

  // Sizing options
  &-lg > .@{inputClass},
  &-lg > &-addon,
  &-lg > &-btn > .@{inputBtn} {
    .input-lg();
  }

  &-sm > .@{inputClass},
  &-sm > &-addon,
  &-sm > &-btn > .@{inputBtn} {
    .input-sm();
  }

  // TODO: input-group-btn-vertical: different button size
}