From c3c75bcc1cb714b0792f8f601d570a05c132ca2c Mon Sep 17 00:00:00 2001
From: David Padilla <davidpadilla.f22@gmail.com>
Date: Wed, 4 Oct 2023 17:56:01 -0500
Subject: [PATCH] fix: rework accordion component animation (#9818)

---
 .../components/Accordion/AccordionItem.tsx    | 32 +++++++++---
 .../scss/components/accordion/_accordion.scss | 50 +++++--------------
 2 files changed, 38 insertions(+), 44 deletions(-)

diff --git a/packages/react/src/components/Accordion/AccordionItem.tsx b/packages/react/src/components/Accordion/AccordionItem.tsx
index e978d0cc7c82..5d279e6f34ad 100644
--- a/packages/react/src/components/Accordion/AccordionItem.tsx
+++ b/packages/react/src/components/Accordion/AccordionItem.tsx
@@ -87,7 +87,7 @@ interface AccordionItemProps {
    * The callback function to run on the `onAnimationEnd`
    * event for the list item.
    */
-  handleAnimationEnd?: AnimationEventHandler<HTMLLIElement>;
+  handleAnimationEnd?: AnimationEventHandler<HTMLElement>;
 }
 
 interface AccordionToggleProps {
@@ -117,7 +117,6 @@ function AccordionItem({
   ...rest
 }: PropsWithChildren<AccordionItemProps>) {
   const [isOpen, setIsOpen] = useState(open);
-  const [animation, setAnimation] = useState('');
   const accordionState = useContext(AccordionContext);
 
   const disabledIsControlled = typeof controlledDisabled === 'boolean';
@@ -130,7 +129,6 @@ function AccordionItem({
   const className = cx({
     [`${prefix}--accordion__item`]: true,
     [`${prefix}--accordion__item--active`]: isOpen,
-    [`${prefix}--accordion__item--${animation}`]: animation,
     [`${prefix}--accordion__item--disabled`]: disabled,
     [customClassName]: !!customClassName,
   });
@@ -140,8 +138,24 @@ function AccordionItem({
   // When the AccordionItem heading is clicked, toggle the open state of the
   // panel
   function onClick(event) {
+    const toggleElement = event.target;
+
+    let content = toggleElement.nextElementSibling;
+
+    // when toggle element is not the button
+    if (toggleElement.nodeName !== 'BUTTON') {
+      content = toggleElement.parentElement.nextElementSibling;
+    }
+
+    if (content.style.maxBlockSize) {
+      // accordion closes
+      content.style.maxBlockSize = null;
+    } else {
+      // accordion opens
+      content.style.maxBlockSize = content.scrollHeight + 15 + 'px';
+    }
+
     const nextValue = !isOpen;
-    setAnimation(isOpen ? '' : 'expanding');
     setIsOpen(nextValue);
     if (onHeadingClick) {
       // TODO: normalize signature, potentially:
@@ -164,7 +178,7 @@ function AccordionItem({
   }
 
   return (
-    <li className={className} {...rest} onAnimationEnd={onAnimationEnd}>
+    <li className={className} {...rest}>
       <Toggle
         disabled={disabled}
         aria-controls={id}
@@ -178,8 +192,12 @@ function AccordionItem({
           {title}
         </Text>
       </Toggle>
-      <div id={id} className={`${prefix}--accordion__content`}>
-        {children}
+      <div
+        className={`${prefix}--accordion__wrapper`}
+        onTransitionEnd={onAnimationEnd}>
+        <div id={id} className={`${prefix}--accordion__content`}>
+          {children}
+        </div>
       </div>
     </li>
   );
diff --git a/packages/styles/scss/components/accordion/_accordion.scss b/packages/styles/scss/components/accordion/_accordion.scss
index 66ab3a346971..3629614a3aeb 100644
--- a/packages/styles/scss/components/accordion/_accordion.scss
+++ b/packages/styles/scss/components/accordion/_accordion.scss
@@ -59,7 +59,6 @@ $content-padding: 0 0 0 $spacing-05 !default;
     display: list-item;
     overflow: visible;
     border-block-start: 1px solid $border-subtle;
-    transition: all $duration-fast-02 motion(standard, productive);
 
     &:last-child {
       border-block-end: 1px solid $border-subtle;
@@ -144,11 +143,18 @@ $content-padding: 0 0 0 $spacing-05 !default;
     text-align: start;
   }
 
+  .#{$prefix}--accordion__wrapper {
+    // Properties for when the accordion closes
+    padding: 0;
+    max-block-size: 0;
+    opacity: 0;
+    transition: all $duration-fast-02 motion(entrance, productive);
+    writing-mode: horizontal-tb;
+  }
+
   .#{$prefix}--accordion__content {
-    display: none;
+    overflow: hidden;
     padding-inline: layout.density('padding-inline');
-    // Transition property for when the accordion closes
-    transition: padding motion(standard, productive) $duration-fast-02;
 
     // Custom breakpoints based on issue #4993
     @include breakpoint-up(480px) {
@@ -189,44 +195,14 @@ $content-padding: 0 0 0 $spacing-05 !default;
     display: block;
   }
 
-  @keyframes collapse-accordion {
-    0% {
-      @include -content-visible;
-    }
-
-    100% {
-      @include -content-hidden;
-    }
-  }
-
-  @keyframes expand-accordion {
-    0% {
-      @include -content-hidden;
-    }
-
-    100% {
-      @include -content-visible;
-    }
-  }
-
-  .#{$prefix}--accordion__item--collapsing .#{$prefix}--accordion__content {
-    animation: $duration-fast-02 motion(standard, productive) collapse-accordion;
-  }
-
-  .#{$prefix}--accordion__item--expanding .#{$prefix}--accordion__content {
-    animation: $duration-fast-02 motion(standard, productive) expand-accordion;
-  }
-
   .#{$prefix}--accordion__item--active {
     overflow: visible;
 
-    .#{$prefix}--accordion__content {
-      display: block;
+    .#{$prefix}--accordion__wrapper {
+      // Properties for when the accordion opens
+      opacity: 1;
       padding-block: $spacing-03;
       padding-block-end: $spacing-06;
-      // Transition property for when the accordion opens
-      transition: padding-top motion(entrance, productive) $duration-fast-02,
-        padding-bottom motion(entrance, productive) $duration-fast-02;
     }
 
     .#{$prefix}--accordion__arrow {