v4: Disabled link cleanup

manual backport of #34886

per https://www.w3.org/TR/html-aria/#docconformance

> It is NOT RECOMMENDED to use `aria-disabled="true"` on an `a` element with an `href` attribute.
>
>NOTE
>If a link needs to be "disabled", remove the `href` attribute.

This PR removes the unnecessary `href="#"`, `tabindex="-1"`, and `aria-disabled="true"` from disabled links in both docs pages and examples. `aria-disabled="true"` *is* kept for disabled link-based buttons (that have `role="button"`) as there it's appropriate to use (you *want* to convey to assistive technologies that this thing you're claiming is a button is also disabled at the moment)

Further, the PR extends the "Link functionality caveat" to show the "proper" way (removing `href` and adding `.disabled` class only) to disable a link, but then explains what to do if that's not possible (and then keeps an example with all the traditional `href="#" tabindex="-1" aria-disabled="true"`, but explains clearly that it's not ideal). Same sort of explanation is also added to the pointer event utilities page

site/content/docs/4.6/components/buttons.md

@@ -101,18 +101,22 @@ Disabled buttons using the `<a>` element behave a bit different:
 
 - `<a>`s don't support the `disabled` attribute, so you must add the `.disabled` class to make it visually appear disabled.
 - Some future-friendly styles are included to disable all `pointer-events` on anchor buttons. In browsers which support that property, you won't see the disabled cursor at all.
-- Disabled buttons should include the `aria-disabled="true"` attribute to indicate the state of the element to assistive technologies.
+- Disabled buttons using `<a>` should include the `aria-disabled="true"` attribute to indicate the state of the element to assistive technologies.
+- Disabled buttons using `<a>` *should not* include the `href` attribute.
 
 {{< example >}}
-<a href="#" class="btn btn-primary btn-lg disabled" tabindex="-1" role="button" aria-disabled="true">Primary link</a>
-<a href="#" class="btn btn-secondary btn-lg disabled" tabindex="-1" role="button" aria-disabled="true">Link</a>
+<a class="btn btn-primary btn-lg disabled" role="button" aria-disabled="true">Primary link</a>
+<a class="btn btn-secondary btn-lg disabled" role="button" aria-disabled="true">Link</a>
 {{< /example >}}
 
-{{< callout warning >}}
-##### Link functionality caveat
+### Link functionality caveat
 
-The `.disabled` class uses `pointer-events: none` to try to disable the link functionality of `<a>`s, but that CSS property is not yet standardized. In addition, even in browsers that do support `pointer-events: none`, keyboard navigation remains unaffected, meaning that sighted keyboard users and users of assistive technologies will still be able to activate these links. So to be safe, add a `tabindex="-1"` attribute on these links (to prevent them from receiving keyboard focus) and use custom JavaScript to disable their functionality.
-{{< /callout >}}
+To cover cases where you have to keep the `href` attribute on a disabled link, the `.disabled` class uses `pointer-events: none` to try to disable the link functionality of `<a>`s. Note that this CSS property is not yet standardized for HTML, but all modern browsers support it. In addition, even in browsers that do support `pointer-events: none`, keyboard navigation remains unaffected, meaning that sighted keyboard users and users of assistive technologies will still be able to activate these links. So to be safe, in addition to `aria-disabled="true"`, also include a `tabindex="-1"` attribute on these links to prevent them from receiving keyboard focus, and use custom JavaScript to disable their functionality altogether.
+
+{{< example >}}
+<a href="#" class="btn btn-primary btn-lg disabled" tabindex="-1" role="button" aria-disabled="true">Primary link</a>
+<a href="#" class="btn btn-secondary btn-lg disabled" tabindex="-1" role="button" aria-disabled="true">Link</a>
+{{< /example >}}
 
 ## Button plugin
 

site/content/docs/4.6/components/card.md

@@ -309,7 +309,7 @@ Add some navigation to a card's header (or block) with Bootstrap's [nav componen
         <a class="nav-link" href="#">Link</a>
       </li>
       <li class="nav-item">
-        <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+        <a class="nav-link disabled">Disabled</a>
       </li>
     </ul>
   </div>
@@ -332,7 +332,7 @@ Add some navigation to a card's header (or block) with Bootstrap's [nav componen
         <a class="nav-link" href="#">Link</a>
       </li>
       <li class="nav-item">
-        <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+        <a class="nav-link disabled">Disabled</a>
       </li>
     </ul>
   </div>

site/content/docs/4.6/components/dropdowns.md

@@ -580,7 +580,7 @@ Add `.disabled` to items in the dropdown to **style them as disabled**.
 {{< example >}}
 <div class="dropdown-menu">
   <a class="dropdown-item" href="#">Regular link</a>
-  <a class="dropdown-item disabled" href="#" tabindex="-1" aria-disabled="true">Disabled link</a>
+  <a class="dropdown-item disabled">Disabled link</a>
   <a class="dropdown-item" href="#">Another link</a>
 </div>
 {{< /example >}}

site/content/docs/4.6/components/list-group.md

@@ -62,7 +62,7 @@ Be sure to **not use the standard `.btn` classes here**.
   <a href="#" class="list-group-item list-group-item-action">A second link item</a>
   <a href="#" class="list-group-item list-group-item-action">A third link item</a>
   <a href="#" class="list-group-item list-group-item-action">A fourth link item</a>
-  <a href="#" class="list-group-item list-group-item-action disabled" tabindex="-1" aria-disabled="true">A disabled link item</a>
+  <a class="list-group-item list-group-item-action disabled">A disabled link item</a>
 </div>
 {{< /example >}}
 

site/content/docs/4.6/components/navbar.md

@@ -61,7 +61,7 @@ Here's an example of all the sub-components included in a responsive light-theme
         </div>
       </li>
       <li class="nav-item">
-        <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+        <a class="nav-link disabled">Disabled</a>
       </li>
     </ul>
     <form class="form-inline my-2 my-lg-0">
@@ -135,7 +135,7 @@ Active states—with `.active`—to indicate the current page can be applied dir
         <a class="nav-link" href="#">Pricing</a>
       </li>
       <li class="nav-item">
-        <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+        <a class="nav-link disabled">Disabled</a>
       </li>
     </ul>
   </div>
@@ -155,7 +155,7 @@ And because we use classes for our navs, you can avoid the list-based approach e
       <a class="nav-link active" href="#">Home <span class="sr-only">(current)</span></a>
       <a class="nav-link" href="#">Features</a>
       <a class="nav-link" href="#">Pricing</a>
-      <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+      <a class="nav-link disabled">Disabled</a>
     </div>
   </div>
 </nav>
@@ -472,7 +472,7 @@ Here's an example navbar using `.navbar-nav-scroll` with `style="max-height: 100
         </ul>
       </li>
       <li class="nav-item">
-        <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Link</a>
+        <a class="nav-link disabled">Link</a>
       </li>
     </ul>
     <form class="d-flex">
@@ -510,7 +510,7 @@ With no `.navbar-brand` shown at the smallest breakpoint:
         <a class="nav-link" href="#">Link</a>
       </li>
       <li class="nav-item">
-        <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+        <a class="nav-link disabled">Disabled</a>
       </li>
     </ul>
     <form class="form-inline my-2 my-lg-0">
@@ -539,7 +539,7 @@ With a brand name shown on the left and toggler on the right:
         <a class="nav-link" href="#">Link</a>
       </li>
       <li class="nav-item">
-        <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+        <a class="nav-link disabled">Disabled</a>
       </li>
     </ul>
     <form class="form-inline my-2 my-lg-0">
@@ -568,7 +568,7 @@ With a toggler on the left and brand name on the right:
         <a class="nav-link" href="#">Link</a>
       </li>
       <li class="nav-item">
-        <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+        <a class="nav-link disabled">Disabled</a>
       </li>
     </ul>
     <form class="form-inline my-2 my-lg-0">

site/content/docs/4.6/components/navs.md

@@ -28,7 +28,7 @@ The base `.nav` component does not include any `.active` state. The following ex
     <a class="nav-link" href="#">Link</a>
   </li>
   <li class="nav-item">
-    <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+    <a class="nav-link disabled">Disabled</a>
   </li>
 </ul>
 {{< /example >}}
@@ -40,7 +40,7 @@ Classes are used throughout, so your markup can be super flexible. Use `<ul>`s l
   <a class="nav-link active" href="#">Active</a>
   <a class="nav-link" href="#">Link</a>
   <a class="nav-link" href="#">Link</a>
-  <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+  <a class="nav-link disabled">Disabled</a>
 </nav>
 {{< /example >}}
 
@@ -66,7 +66,7 @@ Centered with `.justify-content-center`:
     <a class="nav-link" href="#">Link</a>
   </li>
   <li class="nav-item">
-    <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+    <a class="nav-link disabled">Disabled</a>
   </li>
 </ul>
 {{< /example >}}
@@ -85,7 +85,7 @@ Right-aligned with `.justify-content-end`:
     <a class="nav-link" href="#">Link</a>
   </li>
   <li class="nav-item">
-    <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+    <a class="nav-link disabled">Disabled</a>
   </li>
 </ul>
 {{< /example >}}
@@ -106,7 +106,7 @@ Stack your navigation by changing the flex item direction with the `.flex-column
     <a class="nav-link" href="#">Link</a>
   </li>
   <li class="nav-item">
-    <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+    <a class="nav-link disabled">Disabled</a>
   </li>
 </ul>
 {{< /example >}}
@@ -118,7 +118,7 @@ As always, vertical navigation is possible without `<ul>`s, too.
   <a class="nav-link active" href="#">Active</a>
   <a class="nav-link" href="#">Link</a>
   <a class="nav-link" href="#">Link</a>
-  <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+  <a class="nav-link disabled">Disabled</a>
 </nav>
 {{< /example >}}
 
@@ -138,7 +138,7 @@ Takes the basic nav from above and adds the `.nav-tabs` class to generate a tabb
     <a class="nav-link" href="#">Link</a>
   </li>
   <li class="nav-item">
-    <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+    <a class="nav-link disabled">Disabled</a>
   </li>
 </ul>
 {{< /example >}}
@@ -159,7 +159,7 @@ Take that same HTML, but use `.nav-pills` instead:
     <a class="nav-link" href="#">Link</a>
   </li>
   <li class="nav-item">
-    <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+    <a class="nav-link disabled">Disabled</a>
   </li>
 </ul>
 {{< /example >}}
@@ -180,7 +180,7 @@ Force your `.nav`'s contents to extend the full available width one of two modif
     <a class="nav-link" href="#">Link</a>
   </li>
   <li class="nav-item">
-    <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+    <a class="nav-link disabled">Disabled</a>
   </li>
 </ul>
 {{< /example >}}
@@ -192,7 +192,7 @@ When using a `<nav>`-based navigation, you can safely omit `.nav-item` as only `
   <a class="nav-link active" href="#">Active</a>
   <a class="nav-link" href="#">Much longer nav link</a>
   <a class="nav-link" href="#">Link</a>
-  <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+  <a class="nav-link disabled">Disabled</a>
 </nav>
 {{< /example >}}
 
@@ -210,7 +210,7 @@ For equal-width elements, use `.nav-justified`. All horizontal space will be occ
     <a class="nav-link" href="#">Link</a>
   </li>
   <li class="nav-item">
-    <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+    <a class="nav-link disabled">Disabled</a>
   </li>
 </ul>
 {{< /example >}}
@@ -222,7 +222,7 @@ Similar to the `.nav-fill` example using a `<nav>`-based navigation.
   <a class="nav-link active" href="#">Active</a>
   <a class="nav-link" href="#">Much longer nav link</a>
   <a class="nav-link" href="#">Link</a>
-  <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+  <a class="nav-link disabled">Disabled</a>
 </nav>
 
 {{< /example >}}
@@ -235,7 +235,7 @@ If you need responsive nav variations, consider using a series of [flexbox utili
   <a class="flex-sm-fill text-sm-center nav-link active" href="#">Active</a>
   <a class="flex-sm-fill text-sm-center nav-link" href="#">Longer nav link</a>
   <a class="flex-sm-fill text-sm-center nav-link" href="#">Link</a>
-  <a class="flex-sm-fill text-sm-center nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+  <a class="flex-sm-fill text-sm-center nav-link disabled">Disabled</a>
 </nav>
 {{< /example >}}
 
@@ -270,7 +270,7 @@ Add dropdown menus with a little extra HTML and the [dropdowns JavaScript plugin
     <a class="nav-link" href="#">Link</a>
   </li>
   <li class="nav-item">
-    <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+    <a class="nav-link disabled">Disabled</a>
   </li>
 </ul>
 {{< /example >}}
@@ -296,7 +296,7 @@ Add dropdown menus with a little extra HTML and the [dropdowns JavaScript plugin
     <a class="nav-link" href="#">Link</a>
   </li>
   <li class="nav-item">
-    <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+    <a class="nav-link disabled">Disabled</a>
   </li>
 </ul>
 {{< /example >}}

site/content/docs/4.6/components/pagination.md

@@ -58,7 +58,7 @@ While the `.disabled` class uses `pointer-events: none` to _try_ to disable the
 <nav aria-label="...">
   <ul class="pagination">
     <li class="page-item disabled">
-      <a class="page-link" href="#" tabindex="-1" aria-disabled="true">Previous</a>
+      <a class="page-link">Previous</a>
     </li>
     <li class="page-item"><a class="page-link" href="#">1</a></li>
     <li class="page-item active" aria-current="page">
@@ -128,7 +128,7 @@ Change the alignment of pagination components with [flexbox utilities]({{< docsr
 <nav aria-label="Page navigation example">
   <ul class="pagination justify-content-center">
     <li class="page-item disabled">
-      <a class="page-link" href="#" tabindex="-1" aria-disabled="true">Previous</a>
+      <a class="page-link">Previous</a>
     </li>
     <li class="page-item"><a class="page-link" href="#">1</a></li>
     <li class="page-item"><a class="page-link" href="#">2</a></li>
@@ -144,7 +144,7 @@ Change the alignment of pagination components with [flexbox utilities]({{< docsr
 <nav aria-label="Page navigation example">
   <ul class="pagination justify-content-end">
     <li class="page-item disabled">
-      <a class="page-link" href="#" tabindex="-1" aria-disabled="true">Previous</a>
+      <a class="page-link">Previous</a>
     </li>
     <li class="page-item"><a class="page-link" href="#">1</a></li>
     <li class="page-item"><a class="page-link" href="#">2</a></li>

site/content/docs/4.6/examples/blog/index.html

@@ -149,7 +149,7 @@ <h2 class="blog-post-title">New feature</h2>
 
       <nav class="blog-pagination">
         <a class="btn btn-outline-primary" href="#">Older</a>
-        <a class="btn btn-outline-secondary disabled" href="#" tabindex="-1" aria-disabled="true">Newer</a>
+        <a class="btn btn-outline-secondary disabled">Newer</a>
       </nav>
 
     </div><!-- /.blog-main -->

site/content/docs/4.6/examples/carousel/index.html

@@ -20,7 +20,7 @@
           <a class="nav-link" href="#">Link</a>
         </li>
         <li class="nav-item">
-          <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+          <a class="nav-link disabled">Disabled</a>
         </li>
       </ul>
       <form class="form-inline mt-2 mt-md-0">

site/content/docs/4.6/examples/jumbotron/index.html

@@ -20,7 +20,7 @@
         <a class="nav-link" href="#">Link</a>
       </li>
       <li class="nav-item">
-        <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+        <a class="nav-link disabled">Disabled</a>
       </li>
       <li class="nav-item dropdown">
         <a class="nav-link dropdown-toggle" href="#" id="dropdown01" data-toggle="dropdown" aria-expanded="false">Dropdown</a>

site/content/docs/4.6/examples/navbar-bottom/index.html

@@ -24,7 +24,7 @@ <h1>Bottom Navbar example</h1>
         <a class="nav-link" href="#">Link</a>
       </li>
       <li class="nav-item">
-        <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+        <a class="nav-link disabled">Disabled</a>
       </li>
       <li class="nav-item dropup">
         <a class="nav-link dropdown-toggle" href="#" id="dropdown10" data-toggle="dropdown" aria-expanded="false">Dropup</a>

site/content/docs/4.6/examples/navbar-fixed/index.html

@@ -19,7 +19,7 @@
         <a class="nav-link" href="#">Link</a>
       </li>
       <li class="nav-item">
-        <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+        <a class="nav-link disabled">Disabled</a>
       </li>
     </ul>
     <form class="form-inline mt-2 mt-md-0">

site/content/docs/4.6/examples/navbar-static/index.html

@@ -19,7 +19,7 @@
         <a class="nav-link" href="#">Link</a>
       </li>
       <li class="nav-item">
-        <a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
+        <a class="nav-link disabled">Disabled</a>
       </li>
     </ul>
     <form class="form-inline mt-2 mt-md-0">