fix(rule): add custom message for nested-interactive.

aria-hidden and negative tabindex will trigger messageKey.

lib/checks/keyboard/no-focusable-content-for-nested-interactive-evaluate.js

@@ -1,32 +1,49 @@
 import isFocusable from '../../commons/dom/is-focusable';
+import { tokenList } from '../../core/utils';
 
-function focusableDescendants(vNode) {
-  if (isFocusable(vNode)) {
-    return true;
-  }
-
+function getFocusableDescendants(vNode) {
   if (!vNode.children) {
     if (vNode.props.nodeType === 1) {
       throw new Error('Cannot determine children');
     }
 
-    return false;
+    return [];
   }
 
-  return vNode.children.some(child => {
-    return focusableDescendants(child);
+  let retVal = [];
+  vNode.children.forEach(child => {
+    if(isFocusable(child)) {
+      retVal.push(child);
+    } else {
+      getFocusableDescendants(child).forEach(descendantOfChild => retVal.push(descendantOfChild));
+    }
   });
+  return retVal;
+}
+
+function usesUnreliableHidingStrategy(vNode) {
+  let tabIndex = parseInt(vNode.attr('tabindex'), 10);
+  return !isNaN(tabIndex) && tabIndex < 0 && vNode.attr('aria-hidden') == 'true';
 }
 
 function noFocusableContentForNestedInteractiveEvaluate(node, options, virtualNode) {
   if (!virtualNode.children) {
     return undefined;
   }
-
   try {
-    return !virtualNode.children.some(child => {
-      return focusableDescendants(child);
-    });
+    let focusableDescendants = getFocusableDescendants(virtualNode);
+    if(focusableDescendants.length > 0) {
+      let focusableDescendantsThatUseUnreliableHidingStrategy = focusableDescendants.filter(
+        descendant => usesUnreliableHidingStrategy(descendant));
+      if(focusableDescendantsThatUseUnreliableHidingStrategy.length > 0) {
+        let ids = focusableDescendantsThatUseUnreliableHidingStrategy.map(node => node.attr('id'));
+        let n = focusableDescendantsThatUseUnreliableHidingStrategy.length;
+        let msg = `Using aria-hidden and negative tabindex is not a reliable way of hiding interactive elements.  `
+          +`Element ids: [${ids.map(id => '"'+id+'"')}].`;
+        this.data({messageKey: 'info', values: msg});
+      }
+    }
+    return focusableDescendants.length == 0;
   } catch (e) {
     return undefined;
   }