Upgrade to Bootstrap 5

_sass/bootstrap/_accordion.scss

@@ -0,0 +1,158 @@
+//
+// Base styles
+//
+
+.accordion {
+  // scss-docs-start accordion-css-vars
+  --#{$prefix}accordion-color: #{$accordion-color};
+  --#{$prefix}accordion-bg: #{$accordion-bg};
+  --#{$prefix}accordion-transition: #{$accordion-transition};
+  --#{$prefix}accordion-border-color: #{$accordion-border-color};
+  --#{$prefix}accordion-border-width: #{$accordion-border-width};
+  --#{$prefix}accordion-border-radius: #{$accordion-border-radius};
+  --#{$prefix}accordion-inner-border-radius: #{$accordion-inner-border-radius};
+  --#{$prefix}accordion-btn-padding-x: #{$accordion-button-padding-x};
+  --#{$prefix}accordion-btn-padding-y: #{$accordion-button-padding-y};
+  --#{$prefix}accordion-btn-color: #{$accordion-button-color};
+  --#{$prefix}accordion-btn-bg: #{$accordion-button-bg};
+  --#{$prefix}accordion-btn-icon: #{escape-svg($accordion-button-icon)};
+  --#{$prefix}accordion-btn-icon-width: #{$accordion-icon-width};
+  --#{$prefix}accordion-btn-icon-transform: #{$accordion-icon-transform};
+  --#{$prefix}accordion-btn-icon-transition: #{$accordion-icon-transition};
+  --#{$prefix}accordion-btn-active-icon: #{escape-svg($accordion-button-active-icon)};
+  --#{$prefix}accordion-btn-focus-box-shadow: #{$accordion-button-focus-box-shadow};
+  --#{$prefix}accordion-body-padding-x: #{$accordion-body-padding-x};
+  --#{$prefix}accordion-body-padding-y: #{$accordion-body-padding-y};
+  --#{$prefix}accordion-active-color: #{$accordion-button-active-color};
+  --#{$prefix}accordion-active-bg: #{$accordion-button-active-bg};
+  // scss-docs-end accordion-css-vars
+}
+
+.accordion-button {
+  position: relative;
+  display: flex;
+  align-items: center;
+  width: 100%;
+  padding: var(--#{$prefix}accordion-btn-padding-y) var(--#{$prefix}accordion-btn-padding-x);
+  @include font-size($font-size-base);
+  color: var(--#{$prefix}accordion-btn-color);
+  text-align: left; // Reset button style
+  background-color: var(--#{$prefix}accordion-btn-bg);
+  border: 0;
+  @include border-radius(0);
+  overflow-anchor: none;
+  @include transition(var(--#{$prefix}accordion-transition));
+
+  &:not(.collapsed) {
+    color: var(--#{$prefix}accordion-active-color);
+    background-color: var(--#{$prefix}accordion-active-bg);
+    box-shadow: inset 0 calc(-1 * var(--#{$prefix}accordion-border-width)) 0 var(--#{$prefix}accordion-border-color); // stylelint-disable-line function-disallowed-list
+
+    &::after {
+      background-image: var(--#{$prefix}accordion-btn-active-icon);
+      transform: var(--#{$prefix}accordion-btn-icon-transform);
+    }
+  }
+
+  // Accordion icon
+  &::after {
+    flex-shrink: 0;
+    width: var(--#{$prefix}accordion-btn-icon-width);
+    height: var(--#{$prefix}accordion-btn-icon-width);
+    margin-left: auto;
+    content: "";
+    background-image: var(--#{$prefix}accordion-btn-icon);
+    background-repeat: no-repeat;
+    background-size: var(--#{$prefix}accordion-btn-icon-width);
+    @include transition(var(--#{$prefix}accordion-btn-icon-transition));
+  }
+
+  &:hover {
+    z-index: 2;
+  }
+
+  &:focus {
+    z-index: 3;
+    outline: 0;
+    box-shadow: var(--#{$prefix}accordion-btn-focus-box-shadow);
+  }
+}
+
+.accordion-header {
+  margin-bottom: 0;
+}
+
+.accordion-item {
+  color: var(--#{$prefix}accordion-color);
+  background-color: var(--#{$prefix}accordion-bg);
+  border: var(--#{$prefix}accordion-border-width) solid var(--#{$prefix}accordion-border-color);
+
+  &:first-of-type {
+    @include border-top-radius(var(--#{$prefix}accordion-border-radius));
+
+    > .accordion-header .accordion-button {
+      @include border-top-radius(var(--#{$prefix}accordion-inner-border-radius));
+    }
+  }
+
+  &:not(:first-of-type) {
+    border-top: 0;
+  }
+
+  // Only set a border-radius on the last item if the accordion is collapsed
+  &:last-of-type {
+    @include border-bottom-radius(var(--#{$prefix}accordion-border-radius));
+
+    > .accordion-header .accordion-button {
+      &.collapsed {
+        @include border-bottom-radius(var(--#{$prefix}accordion-inner-border-radius));
+      }
+    }
+
+    > .accordion-collapse {
+      @include border-bottom-radius(var(--#{$prefix}accordion-border-radius));
+    }
+  }
+}
+
+.accordion-body {
+  padding: var(--#{$prefix}accordion-body-padding-y) var(--#{$prefix}accordion-body-padding-x);
+}
+
+
+// Flush accordion items
+//
+// Remove borders and border-radius to keep accordion items edge-to-edge.
+
+.accordion-flush {
+  > .accordion-item {
+    border-right: 0;
+    border-left: 0;
+    @include border-radius(0);
+
+    &:first-child { border-top: 0; }
+    &:last-child { border-bottom: 0; }
+
+    // stylelint-disable selector-max-class
+    > .accordion-header .accordion-button {
+      &,
+      &.collapsed {
+        @include border-radius(0);
+      }
+    }
+    // stylelint-enable selector-max-class
+
+    > .accordion-collapse {
+      @include border-radius(0);
+    }
+  }
+}
+
+@if $enable-dark-mode {
+  @include color-mode(dark) {
+    .accordion-button::after {
+      --#{$prefix}accordion-btn-icon: #{escape-svg($accordion-button-icon-dark)};
+      --#{$prefix}accordion-btn-active-icon: #{escape-svg($accordion-button-active-icon-dark)};
+    }
+  }
+}

_sass/bootstrap/_alert.scss

@@ -3,11 +3,25 @@
 //
 
 .alert {
+  // scss-docs-start alert-css-vars
+  --#{$prefix}alert-bg: transparent;
+  --#{$prefix}alert-padding-x: #{$alert-padding-x};
+  --#{$prefix}alert-padding-y: #{$alert-padding-y};
+  --#{$prefix}alert-margin-bottom: #{$alert-margin-bottom};
+  --#{$prefix}alert-color: inherit;
+  --#{$prefix}alert-border-color: transparent;
+  --#{$prefix}alert-border: #{$alert-border-width} solid var(--#{$prefix}alert-border-color);
+  --#{$prefix}alert-border-radius: #{$alert-border-radius};
+  --#{$prefix}alert-link-color: inherit;
+  // scss-docs-end alert-css-vars
+
   position: relative;
-  padding: $alert-padding-y $alert-padding-x;
-  margin-bottom: $alert-margin-bottom;
-  border: $alert-border-width solid transparent;
-  @include border-radius($alert-border-radius);
+  padding: var(--#{$prefix}alert-padding-y) var(--#{$prefix}alert-padding-x);
+  margin-bottom: var(--#{$prefix}alert-margin-bottom);
+  color: var(--#{$prefix}alert-color);
+  background-color: var(--#{$prefix}alert-bg);
+  border: var(--#{$prefix}alert-border);
+  @include border-radius(var(--#{$prefix}alert-border-radius));
 }
 
 // Headings for larger alerts
@@ -19,6 +33,7 @@
 // Provide class for links that match alerts
 .alert-link {
   font-weight: $alert-link-font-weight;
+  color: var(--#{$prefix}alert-link-color);
 }
 
 
@@ -27,25 +42,27 @@
 // Expand the right padding and account for the close button's positioning.
 
 .alert-dismissible {
-  padding-right: $close-font-size + $alert-padding-x * 2;
+  padding-right: $alert-dismissible-padding-r;
 
   // Adjust close link position
-  .close {
+  .btn-close {
     position: absolute;
     top: 0;
     right: 0;
-    padding: $alert-padding-y $alert-padding-x;
-    color: inherit;
+    z-index: $stretched-link-z-index + 1;
+    padding: $alert-padding-y * 1.25 $alert-padding-x;
   }
 }
 
 
-// Alternate styles
-//
-// Generate contextual modifier classes for colorizing the alert.
-
-@each $color, $value in $theme-colors {
-  .alert-#{$color} {
-    @include alert-variant(theme-color-level($color, $alert-bg-level), theme-color-level($color, $alert-border-level), theme-color-level($color, $alert-color-level));
+// scss-docs-start alert-modifiers
+// Generate contextual modifier classes for colorizing the alert
+@each $state in map-keys($theme-colors) {
+  .alert-#{$state} {
+    --#{$prefix}alert-color: var(--#{$prefix}#{$state}-text-emphasis);
+    --#{$prefix}alert-bg: var(--#{$prefix}#{$state}-bg-subtle);
+    --#{$prefix}alert-border-color: var(--#{$prefix}#{$state}-border-subtle);
+    --#{$prefix}alert-link-color: var(--#{$prefix}#{$state}-text-emphasis);
   }
 }
+// scss-docs-end alert-modifiers

_sass/bootstrap/_badge.scss

@@ -4,22 +4,26 @@
 // `background-color`.
 
 .badge {
+  // scss-docs-start badge-css-vars
+  --#{$prefix}badge-padding-x: #{$badge-padding-x};
+  --#{$prefix}badge-padding-y: #{$badge-padding-y};
+  @include rfs($badge-font-size, --#{$prefix}badge-font-size);
+  --#{$prefix}badge-font-weight: #{$badge-font-weight};
+  --#{$prefix}badge-color: #{$badge-color};
+  --#{$prefix}badge-border-radius: #{$badge-border-radius};
+  // scss-docs-end badge-css-vars
+
   display: inline-block;
-  padding: $badge-padding-y $badge-padding-x;
-  @include font-size($badge-font-size);
-  font-weight: $badge-font-weight;
+  padding: var(--#{$prefix}badge-padding-y) var(--#{$prefix}badge-padding-x);
+  @include font-size(var(--#{$prefix}badge-font-size));
+  font-weight: var(--#{$prefix}badge-font-weight);
   line-height: 1;
+  color: var(--#{$prefix}badge-color);
   text-align: center;
   white-space: nowrap;
   vertical-align: baseline;
-  @include border-radius($badge-border-radius);
-  @include transition($badge-transition);
-
-  @at-root a#{&} {
-    @include hover-focus {
-      text-decoration: none;
-    }
-  }
+  @include border-radius(var(--#{$prefix}badge-border-radius));
+  @include gradient-bg();
 
   // Empty badges collapse automatically
   &:empty {
@@ -32,23 +36,3 @@
   position: relative;
   top: -1px;
 }
-
-// Pill badges
-//
-// Make them extra rounded with a modifier to replace v3's badges.
-
-.badge-pill {
-  padding-right: $badge-pill-padding-x;
-  padding-left: $badge-pill-padding-x;
-  @include border-radius($badge-pill-border-radius);
-}
-
-// Colors
-//
-// Contextual variations (linked badges get darker on :hover).
-
-@each $color, $value in $theme-colors {
-  .badge-#{$color} {
-    @include badge-variant($value);
-  }
-}

_sass/bootstrap/_breadcrumb.scss

@@ -1,41 +1,40 @@
 .breadcrumb {
+  // scss-docs-start breadcrumb-css-vars
+  --#{$prefix}breadcrumb-padding-x: #{$breadcrumb-padding-x};
+  --#{$prefix}breadcrumb-padding-y: #{$breadcrumb-padding-y};
+  --#{$prefix}breadcrumb-margin-bottom: #{$breadcrumb-margin-bottom};
+  @include rfs($breadcrumb-font-size, --#{$prefix}breadcrumb-font-size);
+  --#{$prefix}breadcrumb-bg: #{$breadcrumb-bg};
+  --#{$prefix}breadcrumb-border-radius: #{$breadcrumb-border-radius};
+  --#{$prefix}breadcrumb-divider-color: #{$breadcrumb-divider-color};
+  --#{$prefix}breadcrumb-item-padding-x: #{$breadcrumb-item-padding-x};
+  --#{$prefix}breadcrumb-item-active-color: #{$breadcrumb-active-color};
+  // scss-docs-end breadcrumb-css-vars
+
   display: flex;
   flex-wrap: wrap;
-  padding: $breadcrumb-padding-y $breadcrumb-padding-x;
-  margin-bottom: $breadcrumb-margin-bottom;
+  padding: var(--#{$prefix}breadcrumb-padding-y) var(--#{$prefix}breadcrumb-padding-x);
+  margin-bottom: var(--#{$prefix}breadcrumb-margin-bottom);
+  @include font-size(var(--#{$prefix}breadcrumb-font-size));
   list-style: none;
-  background-color: $breadcrumb-bg;
-  @include border-radius($breadcrumb-border-radius);
+  background-color: var(--#{$prefix}breadcrumb-bg);
+  @include border-radius(var(--#{$prefix}breadcrumb-border-radius));
 }
 
 .breadcrumb-item {
   // The separator between breadcrumbs (by default, a forward-slash: "/")
   + .breadcrumb-item {
-    padding-left: $breadcrumb-item-padding;
+    padding-left: var(--#{$prefix}breadcrumb-item-padding-x);
 
     &::before {
-      display: inline-block; // Suppress underlining of the separator in modern browsers
-      padding-right: $breadcrumb-item-padding;
-      color: $breadcrumb-divider-color;
-      content: $breadcrumb-divider;
+      float: left; // Suppress inline spacings and underlining of the separator
+      padding-right: var(--#{$prefix}breadcrumb-item-padding-x);
+      color: var(--#{$prefix}breadcrumb-divider-color);
+      content: var(--#{$prefix}breadcrumb-divider, escape-svg($breadcrumb-divider)) #{"/* rtl:"} var(--#{$prefix}breadcrumb-divider, escape-svg($breadcrumb-divider-flipped)) #{"*/"};
     }
   }
 
-  // IE9-11 hack to properly handle hyperlink underlines for breadcrumbs built
-  // without `<ul>`s. The `::before` pseudo-element generates an element
-  // *within* the .breadcrumb-item and thereby inherits the `text-decoration`.
-  //
-  // To trick IE into suppressing the underline, we give the pseudo-element an
-  // underline and then immediately remove it.
-  + .breadcrumb-item:hover::before {
-    text-decoration: underline;
-  }
-  // stylelint-disable-next-line no-duplicate-selectors
-  + .breadcrumb-item:hover::before {
-    text-decoration: none;
-  }
-
   &.active {
-    color: $breadcrumb-active-color;
+    color: var(--#{$prefix}breadcrumb-item-active-color);
   }
 }