Keep Markup: Use original nodes instead of clones (#3365)

plugins/keep-markup/prism-keep-markup.js

@@ -39,8 +39,8 @@
 			}
 
 			var o = {
-				// Clone the original tag to keep all attributes
-				clone: element.cloneNode(false),
+				// Store original element so we can restore it after highlighting
+				element: element,
 				posOpen: pos
 			};
 			data.push(o);
@@ -96,12 +96,13 @@
 					}
 
 					if (nodeState.nodeStart && nodeState.nodeEnd) {
-						// Select the range and wrap it with the clone
+						// Select the range and wrap it with the element
 						var range = document.createRange();
 						range.setStart(nodeState.nodeStart, nodeState.nodeStartPos);
 						range.setEnd(nodeState.nodeEnd, nodeState.nodeEndPos);
-						nodeState.node.clone.appendChild(range.extractContents());
-						range.insertNode(nodeState.node.clone);
+						nodeState.node.element.innerHTML = '';
+						nodeState.node.element.appendChild(range.extractContents());
+						range.insertNode(nodeState.node.element);
 						range.detach();
 
 						// Process is over

tests/plugins/keep-markup/test.js

@@ -62,6 +62,22 @@ describe('Keep Markup', function () {
 		assert.strictEqual(firstPass, secondPass);
 	});
 
+	it('should not clone markup nodes', function () {
+		const pre = document.createElement('pre');
+		pre.className = 'language-javascript drop-tokens';
+		pre.innerHTML = '<code>var <mark>a = <mark>42</mark></mark>;</code>';
+		const code = pre.childNodes[0];
+		const firstNodeRefBefore = code.querySelector('mark');
+		const secondNodeRefBefore = firstNodeRefBefore.querySelector('mark');
+
+		Prism.highlightElement(code);
+		const firstNodeRefAfter = code.querySelector('mark');
+		const secondNodeRefAfter = firstNodeRefAfter.querySelector('mark');
+
+		assert.strictEqual(firstNodeRefBefore, firstNodeRefAfter);
+		assert.strictEqual(secondNodeRefBefore, secondNodeRefAfter);
+	});
+
 	// The markup is removed if it's the last element and the element's name is a single letter: a(nchor), b(old), i(talic)...
 	// https://github.com/PrismJS/prism/issues/1618
 	/*