Dynamic tabs: use buttons rather than links (#32630)

* Dynamic tabs: use buttons rather than links

- change docs
- add mention that tabs should be <button> elements
- tweak styles to neutralise border and background

* Update js unit and visual test accordingly

- replace links with buttons
- make one specific test that uses links instead of buttons, as we still want to support it despite it being non-semantically appropriate
- Leaving a couple of tests for now. The test for removed tabs should be redone so that tabs are removed programmatically (as the approach of having that close button inside the link is invalid and broken markup). The test for dropdowns should be removed together we actually ripping out the handling for dropdowns in the tab.js code (arguably a breaking change, though we discouraged this for a few versions and effectively "deprecated" it)

* Add isolation:isolate to prevent focus being overlapped

https://github.com/twbs/bootstrap/pull/32630#issuecomment-756015766

1 files changed, 37 insertions, 37 deletions

diff --git a/site/content/docs/5.0/components/navs-tabs.md b/site/content/docs/5.0/components/navs-tabs.md
index 72746d5d7f..822aec14c4 100644
--- a/site/content/docs/5.0/components/navs-tabs.md
+++ b/site/content/docs/5.0/components/navs-tabs.md
@@ -308,20 +308,20 @@ Add dropdown menus with a little extra HTML and the [dropdowns JavaScript plugin
 
 Use the tab JavaScript plugin—include it individually or through the compiled `bootstrap.js` file—to extend our navigational tabs and pills to create tabbable panes of local content.
 
-Dynamic tabbed interfaces, as described in the [<abbr title="Web Accessibility Initiative">WAI</abbr> <abbr title="Accessible Rich Internet Applications">ARIA</abbr> Authoring Practices](https://www.w3.org/TR/wai-aria-practices/#tabpanel), require `role="tablist"`, `role="tab"`, `role="tabpanel"`, and additional `aria-` attributes in order to convey their structure, functionality and current state to users of assistive technologies (such as screen readers).
+Dynamic tabbed interfaces, as described in the [<abbr title="Web Accessibility Initiative">WAI</abbr> <abbr title="Accessible Rich Internet Applications">ARIA</abbr> Authoring Practices](https://www.w3.org/TR/wai-aria-practices/#tabpanel), require `role="tablist"`, `role="tab"`, `role="tabpanel"`, and additional `aria-` attributes in order to convey their structure, functionality and current state to users of assistive technologies (such as screen readers). As a best practice, we recommend using `<button>` elements for the tabs, as these are controls that trigger a dynamic change, rather than links that navigate to a new page or location.
 
 Note that dynamic tabbed interfaces should <em>not</em> contain dropdown menus, as this causes both usability and accessibility issues. From a usability perspective, the fact that the currently displayed tab's trigger element is not immediately visible (as it's inside the closed dropdown menu) can cause confusion. From an accessibility point of view, there is currently no sensible way to map this sort of construct to a standard WAI ARIA pattern, meaning that it cannot be easily made understandable to users of assistive technologies.
 
 <div class="bd-example">
   <ul class="nav nav-tabs mb-3" id="myTab" role="tablist">
     <li class="nav-item" role="presentation">
-      <a class="nav-link active" id="home-tab" data-bs-toggle="tab" href="#home" role="tab" aria-controls="home" aria-selected="true">Home</a>
+      <button class="nav-link active" id="home-tab" data-bs-toggle="tab" data-bs-target="#home" type="button" role="tab" aria-controls="home" aria-selected="true">Home</button>
     </li>
     <li class="nav-item" role="presentation">
-      <a class="nav-link" id="profile-tab" data-bs-toggle="tab" href="#profile" role="tab" aria-controls="profile" aria-selected="false">Profile</a>
+      <button class="nav-link" id="profile-tab" data-bs-toggle="tab" data-bs-target="#profile" type="button" role="tab" aria-controls="profile" aria-selected="false">Profile</button>
     </li>
     <li class="nav-item" role="presentation">
-      <a class="nav-link" id="contact-tab" data-bs-toggle="tab" href="#contact" role="tab" aria-controls="contact" aria-selected="false">Contact</a>
+      <button class="nav-link" id="contact-tab" data-bs-toggle="tab" data-bs-target="#contact" type="button" role="tab" aria-controls="contact" aria-selected="false">Contact</button>
     </li>
   </ul>
   <div class="tab-content" id="myTabContent">
@@ -340,13 +340,13 @@ Note that dynamic tabbed interfaces should <em>not</em> contain dropdown menus,
 ```html
 <ul class="nav nav-tabs" id="myTab" role="tablist">
   <li class="nav-item" role="presentation">
-    <a class="nav-link active" id="home-tab" data-bs-toggle="tab" href="#home" role="tab" aria-controls="home" aria-selected="true">Home</a>
+    <button class="nav-link active" id="home-tab" data-bs-toggle="tab" data-bs-target="#home" type="button" role="tab" aria-controls="home" aria-selected="true">Home</button>
   </li>
   <li class="nav-item" role="presentation">
-    <a class="nav-link" id="profile-tab" data-bs-toggle="tab" href="#profile" role="tab" aria-controls="profile" aria-selected="false">Profile</a>
+    <button class="nav-link" id="profile-tab" data-bs-toggle="tab" data-bs-target="#profile" type="button" role="tab" aria-controls="profile" aria-selected="false">Profile</button>
   </li>
   <li class="nav-item" role="presentation">
-    <a class="nav-link" id="contact-tab" data-bs-toggle="tab" href="#contact" role="tab" aria-controls="contact" aria-selected="false">Contact</a>
+    <button class="nav-link" id="contact-tab" data-bs-toggle="tab" data-bs-target="#contact" type="button" role="tab" aria-controls="contact" aria-selected="false">Contact</button>
   </li>
 </ul>
 <div class="tab-content" id="myTabContent">
@@ -361,9 +361,9 @@ To help fit your needs, this works with `<ul>`-based markup, as shown above, or
 <div class="bd-example">
   <nav>
     <div class="nav nav-tabs mb-3" id="nav-tab" role="tablist">
-      <a class="nav-link active" id="nav-home-tab" data-bs-toggle="tab" href="#nav-home" role="tab" aria-controls="nav-home" aria-selected="true">Home</a>
-      <a class="nav-link" id="nav-profile-tab" data-bs-toggle="tab" href="#nav-profile" role="tab" aria-controls="nav-profile" aria-selected="false">Profile</a>
-      <a class="nav-link" id="nav-contact-tab" data-bs-toggle="tab" href="#nav-contact" role="tab" aria-controls="nav-contact" aria-selected="false">Contact</a>
+      <button class="nav-link active" id="nav-home-tab" data-bs-toggle="tab" data-bs-target="#nav-home" type="button" role="tab" aria-controls="nav-home" aria-selected="true">Home</button>
+      <button class="nav-link" id="nav-profile-tab" data-bs-toggle="tab" data-bs-target="#nav-profile" type="button" role="tab" aria-controls="nav-profile" aria-selected="false">Profile</button>
+      <button class="nav-link" id="nav-contact-tab" data-bs-toggle="tab" data-bs-target="#nav-contact" type="button" role="tab" aria-controls="nav-contact" aria-selected="false">Contact</button>
     </div>
   </nav>
   <div class="tab-content" id="nav-tabContent">
@@ -382,9 +382,9 @@ To help fit your needs, this works with `<ul>`-based markup, as shown above, or
 ```html
 <nav>
   <div class="nav nav-tabs" id="nav-tab" role="tablist">
-    <a class="nav-link active" id="nav-home-tab" data-bs-toggle="tab" href="#nav-home" role="tab" aria-controls="nav-home" aria-selected="true">Home</a>
-    <a class="nav-link" id="nav-profile-tab" data-bs-toggle="tab" href="#nav-profile" role="tab" aria-controls="nav-profile" aria-selected="false">Profile</a>
-    <a class="nav-link" id="nav-contact-tab" data-bs-toggle="tab" href="#nav-contact" role="tab" aria-controls="nav-contact" aria-selected="false">Contact</a>
+    <button class="nav-link active" id="nav-home-tab" data-bs-toggle="tab" data-bs-target="#nav-home" type="button" role="tab" aria-controls="nav-home" aria-selected="true">Home</button>
+    <button class="nav-link" id="nav-profile-tab" data-bs-toggle="tab" data-bs-target="#nav-profile" type="button" role="tab" aria-controls="nav-profile" aria-selected="false">Profile</button>
+    <button class="nav-link" id="nav-contact-tab" data-bs-toggle="tab" data-bs-target="#nav-contact" type="button" role="tab" aria-controls="nav-contact" aria-selected="false">Contact</button>
   </div>
 </nav>
 <div class="tab-content" id="nav-tabContent">
@@ -399,13 +399,13 @@ The tabs plugin also works with pills.
 <div class="bd-example">
   <ul class="nav nav-pills mb-3" id="pills-tab" role="tablist">
     <li class="nav-item" role="presentation">
-      <a class="nav-link active" id="pills-home-tab" data-bs-toggle="pill" href="#pills-home" role="tab" aria-controls="pills-home" aria-selected="true">Home</a>
+      <button class="nav-link active" id="pills-home-tab" data-bs-toggle="pill" data-bs-target="#pills-home" type="button" role="tab" aria-controls="pills-home" aria-selected="true">Home</button>
     </li>
     <li class="nav-item" role="presentation">
-      <a class="nav-link" id="pills-profile-tab" data-bs-toggle="pill" href="#pills-profile" role="tab" aria-controls="pills-profile" aria-selected="false">Profile</a>
+      <button class="nav-link" id="pills-profile-tab" data-bs-toggle="pill" data-bs-target="#pills-profile" type="button" role="tab" aria-controls="pills-profile" aria-selected="false">Profile</button>
     </li>
     <li class="nav-item" role="presentation">
-      <a class="nav-link" id="pills-contact-tab" data-bs-toggle="pill" href="#pills-contact" role="tab" aria-controls="pills-contact" aria-selected="false">Contact</a>
+      <button class="nav-link" id="pills-contact-tab" data-bs-toggle="pill" data-bs-target="#pills-contact" type="button" role="tab" aria-controls="pills-contact" aria-selected="false">Contact</button>
     </li>
   </ul>
   <div class="tab-content" id="pills-tabContent">
@@ -424,13 +424,13 @@ The tabs plugin also works with pills.
 ```html
 <ul class="nav nav-pills mb-3" id="pills-tab" role="tablist">
   <li class="nav-item" role="presentation">
-    <a class="nav-link active" id="pills-home-tab" data-bs-toggle="pill" href="#pills-home" role="tab" aria-controls="pills-home" aria-selected="true">Home</a>
+    <button class="nav-link active" id="pills-home-tab" data-bs-toggle="pill" data-bs-target="#pills-home" type="button" role="tab" aria-controls="pills-home" aria-selected="true">Home</button>
   </li>
   <li class="nav-item" role="presentation">
-    <a class="nav-link" id="pills-profile-tab" data-bs-toggle="pill" href="#pills-profile" role="tab" aria-controls="pills-profile" aria-selected="false">Profile</a>
+    <button class="nav-link" id="pills-profile-tab" data-bs-toggle="pill" data-bs-target="#pills-profile" type="button" role="tab" aria-controls="pills-profile" aria-selected="false">Profile</button>
   </li>
   <li class="nav-item" role="presentation">
-    <a class="nav-link" id="pills-contact-tab" data-bs-toggle="pill" href="#pills-contact" role="tab" aria-controls="pills-contact" aria-selected="false">Contact</a>
+    <button class="nav-link" id="pills-contact-tab" data-bs-toggle="pill" data-bs-target="#pills-contact" type="button" role="tab" aria-controls="pills-contact" aria-selected="false">Contact</button>
   </li>
 </ul>
 <div class="tab-content" id="pills-tabContent">
@@ -445,10 +445,10 @@ And with vertical pills.
 <div class="bd-example">
   <div class="d-flex align-items-start">
     <div class="nav flex-column nav-pills me-3" id="v-pills-tab" role="tablist" aria-orientation="vertical">
-      <a class="nav-link active" id="v-pills-home-tab" data-bs-toggle="pill" href="#v-pills-home" role="tab" aria-controls="v-pills-home" aria-selected="true">Home</a>
-      <a class="nav-link" id="v-pills-profile-tab" data-bs-toggle="pill" href="#v-pills-profile" role="tab" aria-controls="v-pills-profile" aria-selected="false">Profile</a>
-      <a class="nav-link" id="v-pills-messages-tab" data-bs-toggle="pill" href="#v-pills-messages" role="tab" aria-controls="v-pills-messages" aria-selected="false">Messages</a>
-      <a class="nav-link" id="v-pills-settings-tab" data-bs-toggle="pill" href="#v-pills-settings" role="tab" aria-controls="v-pills-settings" aria-selected="false">Settings</a>
+      <button class="nav-link active" id="v-pills-home-tab" data-bs-toggle="pill" data-bs-target="#v-pills-home" type="button" role="tab" aria-controls="v-pills-home" aria-selected="true">Home</button>
+      <button class="nav-link" id="v-pills-profile-tab" data-bs-toggle="pill" data-bs-target="#v-pills-profile" type="button" role="tab" aria-controls="v-pills-profile" aria-selected="false">Profile</button>
+      <button class="nav-link" id="v-pills-messages-tab" data-bs-toggle="pill" data-bs-target="#v-pills-messages" type="button" role="tab" aria-controls="v-pills-messages" aria-selected="false">Messages</button>
+      <button class="nav-link" id="v-pills-settings-tab" data-bs-toggle="pill" data-bs-target="#v-pills-settings" type="button" role="tab" aria-controls="v-pills-settings" aria-selected="false">Settings</button>
     </div>
     <div class="tab-content" id="v-pills-tabContent">
       <div class="tab-pane fade show active" id="v-pills-home" role="tabpanel" aria-labelledby="v-pills-home-tab">
@@ -470,10 +470,10 @@ And with vertical pills.
 ```html
 <div class="d-flex align-items-start">
   <div class="nav flex-column nav-pills me-3" id="v-pills-tab" role="tablist" aria-orientation="vertical">
-    <a class="nav-link active" id="v-pills-home-tab" data-bs-toggle="pill" href="#v-pills-home" role="tab" aria-controls="v-pills-home" aria-selected="true">Home</a>
-    <a class="nav-link" id="v-pills-profile-tab" data-bs-toggle="pill" href="#v-pills-profile" role="tab" aria-controls="v-pills-profile" aria-selected="false">Profile</a>
-    <a class="nav-link" id="v-pills-messages-tab" data-bs-toggle="pill" href="#v-pills-messages" role="tab" aria-controls="v-pills-messages" aria-selected="false">Messages</a>
-    <a class="nav-link" id="v-pills-settings-tab" data-bs-toggle="pill" href="#v-pills-settings" role="tab" aria-controls="v-pills-settings" aria-selected="false">Settings</a>
+    <button class="nav-link active" id="v-pills-home-tab" data-bs-toggle="pill" data-bs-target="#v-pills-home" type="button" role="tab" aria-controls="v-pills-home" aria-selected="true">Home</button>
+    <button class="nav-link" id="v-pills-profile-tab" data-bs-toggle="pill" data-bs-target="#v-pills-profile" type="button" role="tab" aria-controls="v-pills-profile" aria-selected="false">Profile</buttona>
+    <button class="nav-link" id="v-pills-messages-tab" data-bs-toggle="pill" data-bs-target="#v-pills-messages" type="button" role="tab" aria-controls="v-pills-messages" aria-selected="false">Messages</button>
+    <button class="nav-link" id="v-pills-settings-tab" data-bs-toggle="pill" data-bs-target="#v-pills-settings" type="button" role="tab" aria-controls="v-pills-settings" aria-selected="false">Settings</button>
   </div>
   <div class="tab-content" id="v-pills-tabContent">
     <div class="tab-pane fade show active" id="v-pills-home" role="tabpanel" aria-labelledby="v-pills-home-tab">...</div>
@@ -492,16 +492,16 @@ You can activate a tab or pill navigation without writing any JavaScript by simp
 <!-- Nav tabs -->
 <ul class="nav nav-tabs" id="myTab" role="tablist">
   <li class="nav-item" role="presentation">
-    <a class="nav-link active" id="home-tab" data-bs-toggle="tab" href="#home" role="tab" aria-controls="home" aria-selected="true">Home</a>
+    <button class="nav-link active" id="home-tab" data-bs-toggle="tab" data-bs-target="#home" type="button" role="tab" aria-controls="home" aria-selected="true">Home</button>
   </li>
   <li class="nav-item" role="presentation">
-    <a class="nav-link" id="profile-tab" data-bs-toggle="tab" href="#profile" role="tab" aria-controls="profile" aria-selected="false">Profile</a>
+    <button class="nav-link" id="profile-tab" data-bs-toggle="tab" data-bs-target="#profile" type="button" role="tab" aria-controls="profile" aria-selected="false">Profile</button>
   </li>
   <li class="nav-item" role="presentation">
-    <a class="nav-link" id="messages-tab" data-bs-toggle="tab" href="#messages" role="tab" aria-controls="messages" aria-selected="false">Messages</a>
+    <button class="nav-link" id="messages-tab" data-bs-toggle="tab" data-bs-target="#messages" type="button" role="tab" aria-controls="messages" aria-selected="false">Messages</button>
   </li>
   <li class="nav-item" role="presentation">
-    <a class="nav-link" id="settings-tab" data-bs-toggle="tab" href="#settings" role="tab" aria-controls="settings" aria-selected="false">Settings</a>
+    <button class="nav-link" id="settings-tab" data-bs-toggle="tab" hdata-bs-targetref="#settings" type="button" role="tab" aria-controls="settings" aria-selected="false">Settings</button>
   </li>
 </ul>
 
@@ -561,21 +561,21 @@ To make tabs fade in, add `.fade` to each `.tab-pane`. The first tab pane must a
 
 #### constructor
 
-Activates a tab element and content container. Tab should have either a `data-bs-target` or an `href` targeting a container node in the DOM.
+Activates a tab element and content container. Tab should have either a `data-bs-target` or, if using a link, an `href` attribute, targeting a container node in the DOM.
 
 ```html
 <ul class="nav nav-tabs" id="myTab" role="tablist">
   <li class="nav-item" role="presentation">
-    <a class="nav-link active" id="home-tab" data-bs-toggle="tab" href="#home" role="tab" aria-controls="home" aria-selected="true">Home</a>
+    <button class="nav-link active" id="home-tab" data-bs-toggle="tab" data-bs-target="#home" type="button" role="tab" aria-controls="home" aria-selected="true">Home</button>
   </li>
   <li class="nav-item" role="presentation">
-    <a class="nav-link" id="profile-tab" data-bs-toggle="tab" href="#profile" role="tab" aria-controls="profile" aria-selected="false">Profile</a>
+    <button class="nav-link" id="profile-tab" data-bs-toggle="tab" data-bs-target="#profile" type="button" role="tab" aria-controls="profile" aria-selected="false">Profile</button>
   </li>
   <li class="nav-item" role="presentation">
-    <a class="nav-link" id="messages-tab" data-bs-toggle="tab" href="#messages" role="tab" aria-controls="messages" aria-selected="false">Messages</a>
+    <button class="nav-link" id="messages-tab" data-bs-toggle="tab" data-bs-target="#messages" type="button" role="tab" aria-controls="messages" aria-selected="false">Messages</button>
   </li>
   <li class="nav-item" role="presentation">
-    <a class="nav-link" id="settings-tab" data-bs-toggle="tab" href="#settings" role="tab" aria-controls="settings" aria-selected="false">Settings</a>
+    <button class="nav-link" id="settings-tab" data-bs-toggle="tab" data-bs-target="#settings" type="button" role="tab" aria-controls="settings" aria-selected="false">Settings</button>
   </li>
 </ul>
 
@@ -657,7 +657,7 @@ If no tab was already active, then the `hide.bs.tab` and `hidden.bs.tab` events
 </table>
 
 ```js
-var tabEl = document.querySelector('a[data-bs-toggle="tab"]')
+var tabEl = document.querySelector('button[data-bs-toggle="tab"]')
 tabEl.addEventListener('shown.bs.tab', function (event) {
   event.target // newly activated tab
   event.relatedTarget // previous active tab