Add missing `role="button"` in collapse examples. (#24725)

docs/4.0/components/collapse.md

@@ -18,7 +18,7 @@ You can use a link with the `href` attribute, or a button with the `data-target`
 
 {% example html %}
 <p>
-  <a class="btn btn-primary" data-toggle="collapse" href="#collapseExample" aria-expanded="false" aria-controls="collapseExample">
+  <a class="btn btn-primary" data-toggle="collapse" href="#collapseExample" role="button" aria-expanded="false" aria-controls="collapseExample">
     Link with href
   </a>
   <button class="btn btn-primary" type="button" data-toggle="collapse" data-target="#collapseExample" aria-expanded="false" aria-controls="collapseExample">
@@ -39,7 +39,7 @@ Multiple `<button>` or `<a>` can show and hide an element if they each reference
 
 {% example html %}
 <p>
-  <a class="btn btn-primary" data-toggle="collapse" href="#multiCollapseExample1" aria-expanded="false" aria-controls="multiCollapseExample1">Toggle first element</a>
+  <a class="btn btn-primary" data-toggle="collapse" href="#multiCollapseExample1" role="button" aria-expanded="false" aria-controls="multiCollapseExample1">Toggle first element</a>
   <button class="btn btn-primary" type="button" data-toggle="collapse" data-target="#multiCollapseExample2" aria-expanded="false" aria-controls="multiCollapseExample2">Toggle second element</button>
   <button class="btn btn-primary" type="button" data-toggle="collapse" data-target=".multi-collapse" aria-expanded="false" aria-controls="multiCollapseExample1 multiCollapseExample2">Toggle both elements</button>
 </p>
@@ -70,7 +70,7 @@ Using the [card]({{ site.baseurl }}/docs/{{ site.docs_version }}/components/card
   <div class="card">
     <div class="card-header" role="tab" id="headingOne">
       <h5 class="mb-0">
-        <a data-toggle="collapse" href="#collapseOne" aria-expanded="true" aria-controls="collapseOne">
+        <a data-toggle="collapse" href="#collapseOne" role="button" aria-expanded="true" aria-controls="collapseOne">
           Collapsible Group Item #1
         </a>
       </h5>
@@ -85,7 +85,7 @@ Using the [card]({{ site.baseurl }}/docs/{{ site.docs_version }}/components/card
   <div class="card">
     <div class="card-header" role="tab" id="headingTwo">
       <h5 class="mb-0">
-        <a class="collapsed" data-toggle="collapse" href="#collapseTwo" aria-expanded="false" aria-controls="collapseTwo">
+        <a class="collapsed" data-toggle="collapse" href="#collapseTwo" role="button" aria-expanded="false" aria-controls="collapseTwo">
           Collapsible Group Item #2
         </a>
       </h5>
@@ -99,7 +99,7 @@ Using the [card]({{ site.baseurl }}/docs/{{ site.docs_version }}/components/card
   <div class="card">
     <div class="card-header" role="tab" id="headingThree">
       <h5 class="mb-0">
-        <a class="collapsed" data-toggle="collapse" href="#collapseThree" aria-expanded="false" aria-controls="collapseThree">
+        <a class="collapsed" data-toggle="collapse" href="#collapseThree" role="button" aria-expanded="false" aria-controls="collapseThree">
           Collapsible Group Item #3
         </a>
       </h5>
@@ -118,7 +118,7 @@ You can also create accordions with custom markup. Add the `data-children` attri
 {% example html %}
 <div id="exampleAccordion" data-children=".item">
   <div class="item">
-    <a data-toggle="collapse" data-parent="#exampleAccordion" href="#exampleAccordion1" aria-expanded="true" aria-controls="exampleAccordion1">
+    <a data-toggle="collapse" data-parent="#exampleAccordion" href="#exampleAccordion1" role="button" aria-expanded="true" aria-controls="exampleAccordion1">
       Toggle item
     </a>
     <div id="exampleAccordion1" class="collapse show" role="tabpanel">
@@ -128,7 +128,7 @@ You can also create accordions with custom markup. Add the `data-children` attri
     </div>
   </div>
   <div class="item">
-    <a data-toggle="collapse" data-parent="#exampleAccordion" href="#exampleAccordion2" aria-expanded="false" aria-controls="exampleAccordion2">
+    <a data-toggle="collapse" data-parent="#exampleAccordion" href="#exampleAccordion2" role="button" aria-expanded="false" aria-controls="exampleAccordion2">
       Toggle item 2
     </a>
     <div id="exampleAccordion2" class="collapse" role="tabpanel">
@@ -142,7 +142,7 @@ You can also create accordions with custom markup. Add the `data-children` attri
 
 ## Accessibility
 
-Be sure to add `aria-expanded` to the control element. This attribute explicitly conveys the current state of the collapsible element tied to the control to screen readers and similar assistive technologies. If the collapsible element is closed by default, the attribute on the control element should have a value of `aria-expanded="false"`. If you've set the collapsible element to be open by default using the `show` class, set `aria-expanded="true"` on the control instead. The plugin will automatically toggle this attribute on the control based on whether or not the collapsible element has been opened or closed (via JavaScript, or because the user triggered another control element also tied to the same collapsbile element).
+Be sure to add `aria-expanded` to the control element. This attribute explicitly conveys the current state of the collapsible element tied to the control to screen readers and similar assistive technologies. If the collapsible element is closed by default, the attribute on the control element should have a value of `aria-expanded="false"`. If you've set the collapsible element to be open by default using the `show` class, set `aria-expanded="true"` on the control instead. The plugin will automatically toggle this attribute on the control based on whether or not the collapsible element has been opened or closed (via JavaScript, or because the user triggered another control element also tied to the same collapsbile element). If the control element's HTML element is not a button (e.g., an `<a>` or `<div>`), the attribute `role="button"` should be added to the element.
 
 Additionally, if your control element is targeting a single collapsible element – i.e. the `data-target` attribute is pointing to an `id` selector – you may add an additional `aria-controls` attribute to the control element, containing the `id` of the collapsible element. Modern screen readers and similar assistive technologies make use of this attribute to provide users with additional shortcuts to navigate directly to the collapsible element itself.