From 1e95e0af276363c185adc024b8fa19fe7d41f610 Mon Sep 17 00:00:00 2001
From: Mas0nShi <fishilir@gmail.com>
Date: Thu, 23 Feb 2023 14:14:39 +0800
Subject: [PATCH] #519@patch: Fixes XMLParser Bug.

---
 .../happy-dom/src/xml-parser/XMLParser.ts     | 27 +++++++++++++++-
 .../test/xml-parser/XMLParser.test.ts         | 32 +++++++++++++++++++
 2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/packages/happy-dom/src/xml-parser/XMLParser.ts b/packages/happy-dom/src/xml-parser/XMLParser.ts
index fc704af04..7e552e867 100755
--- a/packages/happy-dom/src/xml-parser/XMLParser.ts
+++ b/packages/happy-dom/src/xml-parser/XMLParser.ts
@@ -13,6 +13,9 @@ import HTMLLinkElement from '../nodes/html-link-element/HTMLLinkElement';
 import IDocumentFragment from '../nodes/document-fragment/IDocumentFragment';
 import PlainTextElements from '../config/PlainTextElements';
 
+const CONDITION_COMMENT_REGEXP =
+	/<!(--)?\[if (!|le|lt|lte|gt|gte|\(.*\)|&|\|| |IE|WindowsEdition|Contoso|true|false|\d+\.?(\d+)?|)*\]>/gi;
+const CONDITION_COMMENT_END_REGEXP = /<!\[endif\](--)?>/gi;
 const MARKUP_REGEXP = /<(\/?)([a-z][-.0-9_a-z]*)\s*([^<>]*?)(\/?)>/gi;
 const COMMENT_REGEXP = /<!--(.*?)-->|<([!?])([^>]*)>/gi;
 const DOCUMENT_TYPE_ATTRIBUTE_REGEXP = /"([^"]+)"/gm;
@@ -56,7 +59,29 @@ export default class XMLParser {
 					if (parentTagName && PlainTextElements.includes(parentTagName)) {
 						parent.appendChild(document.createTextNode(text));
 					} else {
-						this.appendTextAndCommentNodes(document, parent, text);
+						let condCommMatch;
+						let condCommEndMatch;
+						let needRewrite = false;
+						const condCommRegexp = new RegExp(CONDITION_COMMENT_REGEXP, 'gi');
+						const condCommEndRegexp = new RegExp(CONDITION_COMMENT_END_REGEXP, 'gi');
+						// @Refer: https://learn.microsoft.com/en-us/previous-versions/windows/internet-explorer/ie-developer/?redirectedfrom=MSDN
+						if (isStartTag && (condCommMatch = condCommRegexp.exec(text)) && condCommMatch[0]) {
+							// Compatible with IE
+							while ((condCommEndMatch = condCommEndRegexp.exec(data))) {
+								if (condCommEndMatch[0]) {
+									needRewrite = true;
+									break;
+								} else {
+									throw new Error('conditional comments unclosed.');
+								}
+							}
+							if (needRewrite) {
+								markupRegexp.lastIndex = condCommEndRegexp.lastIndex;
+								continue; // Re parse.
+							}
+						} else {
+							this.appendTextAndCommentNodes(document, parent, text);
+						}
 					}
 				}
 
diff --git a/packages/happy-dom/test/xml-parser/XMLParser.test.ts b/packages/happy-dom/test/xml-parser/XMLParser.test.ts
index f30c525f4..664d1aed6 100644
--- a/packages/happy-dom/test/xml-parser/XMLParser.test.ts
+++ b/packages/happy-dom/test/xml-parser/XMLParser.test.ts
@@ -410,5 +410,37 @@ describe('XMLParser', () => {
 			const root4 = XMLParser.parse(window.document, <string>(<unknown>false));
 			expect(new XMLSerializer().serializeToString(root4)).toBe('false');
 		});
+
+		it('Parses conditional comments', () => {
+			const testHTML = [
+				'<!--[if IE 8]>\n' + '<p>Welcome to Internet Explorer 8.</p>\n' + '<![endif]-->',
+
+				'<!--[if gte IE 7]>\n' +
+					'<script>\n' +
+					'  alert("Congratulations! You are running Internet Explorer 7 or a later version of Internet Explorer.");\n' +
+					'</script>\n' +
+					'<p>Thank you for closing the message box.</p>\n' +
+					'<![endif]-->',
+
+				'<!--[if IE 5]>\n' +
+					'<p>Welcome to any incremental version of Internet Explorer 5!</p>\n' +
+					'<![endif]-->',
+
+				'<!--[if IE 5.0000]>\n' + '<p>Welcome to Internet Explorer 5.0!</p>\n' + '<![endif]-->',
+
+				'<!--[if WindowsEdition 1]>\n' +
+					'<p>You are using Windows Ultimate Edition.</p>\n' +
+					'<![endif]-->',
+
+				'<!--[if lt Contoso 2]>\n' +
+					'<p>Your version of the Contoso control is out of date; Please update to the latest.</p>\n' +
+					'<![endif]-->'
+			];
+
+			for (const html of testHTML) {
+				const root = XMLParser.parse(window.document, html);
+				expect(new XMLSerializer().serializeToString(root)).toBe(html);
+			}
+		});
 	});
 });