Fix conflict with Bootstrap CSS

js/src/dropdown.js

@@ -57,7 +57,6 @@ const CLASS_NAME_SHOW = 'show'
 const CLASS_NAME_DROPUP = 'dropup'
 const CLASS_NAME_DROPEND = 'dropend'
 const CLASS_NAME_DROPSTART = 'dropstart'
-const CLASS_NAME_MENUEND = 'dropdown-menu-end'
 const CLASS_NAME_NAVBAR = 'navbar'
 
 const SELECTOR_DATA_TOGGLE = '[data-bs-toggle="dropdown"]'
@@ -268,22 +267,23 @@ class Dropdown extends BaseComponent {
 
   _getPlacement() {
     const parentDropdown = this._element.parentNode
-    let placement = PLACEMENT_BOTTOM
 
-    // Handle dropup
-    if (parentDropdown.classList.contains(CLASS_NAME_DROPUP)) {
-      placement = this._menu.classList.contains(CLASS_NAME_MENUEND) ?
-        PLACEMENT_TOPEND :
-        PLACEMENT_TOP
-    } else if (parentDropdown.classList.contains(CLASS_NAME_DROPEND)) {
-      placement = PLACEMENT_RIGHT
-    } else if (parentDropdown.classList.contains(CLASS_NAME_DROPSTART)) {
-      placement = PLACEMENT_LEFT
-    } else if (this._menu.classList.contains(CLASS_NAME_MENUEND)) {
-      placement = PLACEMENT_BOTTOMEND
+    if (parentDropdown.classList.contains(CLASS_NAME_DROPEND)) {
+      return PLACEMENT_RIGHT
     }
 
-    return placement
+    if (parentDropdown.classList.contains(CLASS_NAME_DROPSTART)) {
+      return PLACEMENT_LEFT
+    }
+
+    // We need to trim the value because custom properties can also include spaces
+    const isEnd = getComputedStyle(this._menu).getPropertyValue('--bs-position').trim() === 'end'
+
+    if (parentDropdown.classList.contains(CLASS_NAME_DROPUP)) {
+      return isEnd ? PLACEMENT_TOPEND : PLACEMENT_TOP
+    }
+
+    return isEnd ? PLACEMENT_BOTTOMEND : PLACEMENT_BOTTOM
   }
 
   _detectNavbar() {

scss/_dropdown.scss

@@ -32,19 +32,29 @@
   border: $dropdown-border-width solid $dropdown-border-color;
   @include border-radius($dropdown-border-radius);
   @include box-shadow($dropdown-box-shadow);
+
+  // Reset positioning when positioned with Popper
+  &[style] {
+    right: auto;
+  }
 }
 
 // scss-docs-start responsive-breakpoints
+// We deliberately hardcode the `bs-` prefix because we check
+// this custom property in JS to determine Popper's positioning
+
 @each $breakpoint in map-keys($grid-breakpoints) {
   @include media-breakpoint-up($breakpoint) {
     $infix: breakpoint-infix($breakpoint, $grid-breakpoints);
 
     .dropdown-menu#{$infix}-start {
+      --bs-position: start;
       right: auto #{"/* rtl:ignore */"};
       left: 0 #{"/* rtl:ignore */"};
     }
 
     .dropdown-menu#{$infix}-end {
+      --bs-position: end;
       right: 0 #{"/* rtl:ignore */"};
       left: auto #{"/* rtl:ignore */"};
     }
@@ -101,19 +111,6 @@
   }
 }
 
-// When Popper is enabled, reset the basic dropdown position
-// stylelint-disable-next-line no-duplicate-selectors
-.dropdown-menu {
-  &[data-popper-placement^="top"],
-  &[data-popper-placement^="right"],
-  &[data-popper-placement^="bottom"],
-  &[data-popper-placement^="left"] {
-    right: auto;
-    bottom: auto;
-    left: auto;
-  }
-}
-
 
 // Dividers (basically an `<hr>`) within the dropdown
 .dropdown-divider {