Update: (Fixes #807) Bootstrap to 8f7bd41 (v4.1.0)

packages/clay/src/scss/bootstrap/_breadcrumb.scss

@@ -5,17 +5,20 @@
   margin-bottom: $breadcrumb-margin-bottom;
   list-style: none;
   background-color: $breadcrumb-bg;
-  @include border-radius($border-radius);
+  @include border-radius($breadcrumb-border-radius);
 }
 
 .breadcrumb-item {
   // The separator between breadcrumbs (by default, a forward-slash: "/")
-  + .breadcrumb-item::before {
-    display: inline-block; // Suppress underlining of the separator in modern browsers
-    padding-right: $breadcrumb-item-padding;
+  + .breadcrumb-item {
     padding-left: $breadcrumb-item-padding;
-    color: $breadcrumb-divider-color;
-    content: "#{$breadcrumb-divider}";
+
+    &::before {
+      display: inline-block; // Suppress underlining of the separator in modern browsers
+      padding-right: $breadcrumb-item-padding;
+      color: $breadcrumb-divider-color;
+      content: $breadcrumb-divider;
+    }
   }
 
   // IE9-11 hack to properly handle hyperlink underlines for breadcrumbs built

packages/clay/src/scss/bootstrap/_button-group.scss

@@ -76,9 +76,15 @@
   padding-right: $btn-padding-x * .75;
   padding-left: $btn-padding-x * .75;
 
-  &::after {
+  &::after,
+  .dropup &::after,
+  .dropright &::after {
     margin-left: 0;
   }
+
+  .dropleft &::before {
+    margin-right: 0;
+  }
 }
 
 .btn-sm + .dropdown-toggle-split {

packages/clay/src/scss/bootstrap/_buttons.scss

@@ -100,6 +100,7 @@ fieldset:disabled a.btn {
   &:disabled,
   &.disabled {
     color: $btn-link-disabled-color;
+    pointer-events: none;
   }
 
   // No need for an active state here

packages/clay/src/scss/bootstrap/_card.scss

@@ -153,7 +153,7 @@
 
     .card {
       display: flex;
-      // Flexbugs #4: https://github.com/philipwalton/flexbugs#4-flex-shorthand-declarations-with-unitless-flex-basis-values-are-ignored
+      // Flexbugs #4: https://github.com/philipwalton/flexbugs#flexbug-4
       flex: 1 0 0%;
       flex-direction: column;
       margin-right: $card-deck-margin;
@@ -183,7 +183,7 @@
     // The child selector allows nested `.card` within `.card-group`
     // to display properly.
     > .card {
-      // Flexbugs #4: https://github.com/philipwalton/flexbugs#4-flex-shorthand-declarations-with-unitless-flex-basis-values-are-ignored
+      // Flexbugs #4: https://github.com/philipwalton/flexbugs#flexbug-4
       flex: 1 0 0%;
       margin-bottom: 0;
 
@@ -261,10 +261,41 @@
   @include media-breakpoint-up(sm) {
     column-count: $card-columns-count;
     column-gap: $card-columns-gap;
+    orphans: 1;
+    widows: 1;
 
     .card {
       display: inline-block; // Don't let them vertically span multiple columns
       width: 100%; // Don't let their width change
     }
   }
 }
+
+
+//
+// Accordion
+//
+
+.accordion {
+  .card:not(:first-of-type):not(:last-of-type) {
+    border-bottom: 0;
+    border-radius: 0;
+  }
+
+  .card:not(:first-of-type) {
+    .card-header:first-child {
+      border-radius: 0;
+    }
+  }
+
+  .card:first-of-type {
+    border-bottom: 0;
+    border-bottom-right-radius: 0;
+    border-bottom-left-radius: 0;
+  }
+
+  .card:last-of-type {
+    border-top-left-radius: 0;
+    border-top-right-radius: 0;
+  }
+}

packages/clay/src/scss/bootstrap/_carousel.scss

@@ -1,4 +1,13 @@
-// Wrapper for the slide container and indicators
+// Notes on the classes:
+//
+// 1. The .carousel-item-left and .carousel-item-right is used to indicate where
+//    the active slide is heading.
+// 2. .active.carousel-item is the current slide.
+// 3. .active.carousel-item-left and .active.carousel-item-right is the current
+//    slide in its in-transition state. Only one of these occurs at a time.
+// 4. .carousel-item-next.carousel-item-left and .carousel-item-prev.carousel-item-right
+//    is the upcoming slide in transition.
+
 .carousel {
   position: relative;
 }
@@ -31,7 +40,6 @@
   top: 0;
 }
 
-// CSS3 transforms when supported by the browser
 .carousel-item-next.carousel-item-left,
 .carousel-item-prev.carousel-item-right {
   transform: translateX(0);
@@ -60,6 +68,42 @@
 }
 
 
+//
+// Alternate transitions
+//
+
+.carousel-fade {
+  .carousel-item {
+    opacity: 0;
+    transition-duration: .6s;
+    transition-property: opacity;
+  }
+
+  .carousel-item.active,
+  .carousel-item-next.carousel-item-left,
+  .carousel-item-prev.carousel-item-right {
+    opacity: 1;
+  }
+
+  .active.carousel-item-left,
+  .active.carousel-item-right {
+    opacity: 0;
+  }
+
+  .carousel-item-next,
+  .carousel-item-prev,
+  .carousel-item.active,
+  .active.carousel-item-left,
+  .active.carousel-item-prev {
+    transform: translateX(0);
+
+    @supports (transform-style: preserve-3d) {
+      transform: translate3d(0, 0, 0);
+    }
+  }
+}
+
+
 //
 // Left/right controls for nav
 //
@@ -91,13 +135,13 @@
 .carousel-control-prev {
   left: 0;
   @if $enable-gradients {
-    background: linear-gradient(90deg, rgba(0, 0, 0, .25), rgba(0, 0, 0, .001));
+    background: linear-gradient(90deg, rgba($black, .25), rgba($black, .001));
   }
 }
 .carousel-control-next {
   right: 0;
   @if $enable-gradients {
-    background: linear-gradient(270deg, rgba(0, 0, 0, .25), rgba(0, 0, 0, .001));
+    background: linear-gradient(270deg, rgba($black, .25), rgba($black, .001));
   }
 }
 

packages/clay/src/scss/bootstrap/_custom-forms.scss

@@ -157,7 +157,7 @@
 // Select
 //
 // Replaces the browser default select with a custom one, mostly pulled from
-// http://primercss.io.
+// https://primer.github.io/.
 //
 
 .custom-select {
@@ -247,11 +247,11 @@
   margin: 0;
   opacity: 0;
 
-  &:focus ~ .custom-file-control {
+  &:focus ~ .custom-file-label {
     border-color: $custom-file-focus-border-color;
     box-shadow: $custom-file-focus-box-shadow;
 
-    &::before {
+    &::after {
       border-color: $custom-file-focus-border-color;
     }
   }
@@ -295,3 +295,126 @@
     @include border-radius(0 $custom-file-border-radius $custom-file-border-radius 0);
   }
 }
+
+// Range
+//
+// Style range inputs the same across browsers. Vendor-specific rules for psuedo
+// elements cannot be mixed. As such, there are no shared styles for focus or
+// active states on prefixed selectors.
+
+.custom-range {
+  width: 100%;
+  padding-left: 0; // Firefox specific
+  background-color: transparent;
+  appearance: none;
+
+  &:focus {
+    outline: none;
+  }
+
+  &::-moz-focus-outer {
+    border: 0;
+  }
+
+  &::-webkit-slider-thumb {
+    width: $custom-range-thumb-width;
+    height: $custom-range-thumb-height;
+    margin-top: -($custom-range-thumb-width * .25); // Webkit specific?
+    @include gradient-bg($custom-range-thumb-bg);
+    border: $custom-range-thumb-border;
+    @include border-radius($custom-range-thumb-border-radius);
+    @include box-shadow($custom-range-thumb-box-shadow);
+    appearance: none;
+
+    &:focus {
+      outline: none;
+      box-shadow: $custom-range-thumb-focus-box-shadow; // No mixin for focus accessibility
+    }
+
+    &:active {
+      @include gradient-bg($custom-range-thumb-active-bg);
+    }
+  }
+
+  &::-webkit-slider-runnable-track {
+    width: $custom-range-track-width;
+    height: $custom-range-track-height;
+    color: transparent; // Why?
+    cursor: $custom-range-track-cursor;
+    background-color: $custom-range-track-bg;
+    border-color: transparent;
+    @include border-radius($custom-range-track-border-radius);
+    @include box-shadow($custom-range-track-box-shadow);
+  }
+
+  &::-moz-range-thumb {
+    width: $custom-range-thumb-width;
+    height: $custom-range-thumb-height;
+    @include gradient-bg($custom-range-thumb-bg);
+    border: $custom-range-thumb-border;
+    @include border-radius($custom-range-thumb-border-radius);
+    @include box-shadow($custom-range-thumb-box-shadow);
+    appearance: none;
+
+    &:focus {
+      outline: none;
+      box-shadow: $custom-range-thumb-focus-box-shadow; // No mixin for focus accessibility
+    }
+
+    &:active {
+      @include gradient-bg($custom-range-thumb-active-bg);
+    }
+  }
+
+  &::-moz-range-track {
+    width: $custom-range-track-width;
+    height: $custom-range-track-height;
+    color: transparent;
+    cursor: $custom-range-track-cursor;
+    background-color: $custom-range-track-bg;
+    border-color: transparent; // Firefox specific?
+    @include border-radius($custom-range-track-border-radius);
+    @include box-shadow($custom-range-track-box-shadow);
+  }
+
+  &::-ms-thumb {
+    width: $custom-range-thumb-width;
+    height: $custom-range-thumb-height;
+    @include gradient-bg($custom-range-thumb-bg);
+    border: $custom-range-thumb-border;
+    @include border-radius($custom-range-thumb-border-radius);
+    @include box-shadow($custom-range-thumb-box-shadow);
+    appearance: none;
+
+    &:focus {
+      outline: none;
+      box-shadow: $custom-range-thumb-focus-box-shadow; // No mixin for focus accessibility
+    }
+
+    &:active {
+      @include gradient-bg($custom-range-thumb-active-bg);
+    }
+  }
+
+  &::-ms-track {
+    width: $custom-range-track-width;
+    height: $custom-range-track-height;
+    color: transparent;
+    cursor: $custom-range-track-cursor;
+    background-color: transparent;
+    border-color: transparent;
+    border-width: ($custom-range-thumb-height * .5);
+    @include box-shadow($custom-range-track-box-shadow);
+  }
+
+  &::-ms-fill-lower {
+    background-color: $custom-range-track-bg;
+    @include border-radius($custom-range-track-border-radius);
+  }
+
+  &::-ms-fill-upper {
+    margin-right: 15px; // arbitrary?
+    background-color: $custom-range-track-bg;
+    @include border-radius($custom-range-track-border-radius);
+  }
+}