MDL-66979: Workaround geckodriver clicking on link containing block

There is a bug in Geckodriver which means that it is unable to click any
link which contains a block level node.

See mozilla/geckodriver#653.

The workaround is to click on it's first descendant instead.

This is achieved thorugh finding it's first child and clicking that
instead.

Note: This is not a perfect workaround as the first child element may
not be the one containing the block element, but normally this situation
only occurs where the only immediate child is a block element.

src/Moodle/BehatExtension/Element/NodeElement.php

@@ -25,6 +25,7 @@
 namespace Moodle\BehatExtension\Element;
 
 use Behat\Mink\Element\NodeElement as MinkNodeElement;
+use Facebook\WebDriver\Exception\NoSuchWindowException;
 
 /**
  * Node Element.
@@ -46,7 +47,20 @@ public function click() {
             $this->ensure_node_is_in_viewport();
         }
 
-        parent::click();
+        try {
+            parent::click();
+        } catch (ElementNotInteractableException $e) {
+            // There is a bug in Geckodriver which means that it is unable to click any link which contains a block
+            // level node. See https://github.com/mozilla/geckodriver/issues/653.
+            // The workaround is to click on it's first descendant instead.
+            if ($child = $this->find('xpath', './*[1]')) {
+                $child->click();
+
+                return;
+            }
+
+            throw $e;
+        }
     }