Issue Summary

In Confluence 11.0, every call to ConfluenceWysiwygConverter#convertXHtmlToWikiMarkup fails with java.lang.NoClassDefFoundError: org/cyberneko/html/parsers/DOMFragmentParser. 

DefaultConfluenceWysiwygConverter calls com.atlassian.renderer.wysiwyg.converter.DefaultWysiwygConverter (atlassian-renderer-legacy 6.5.4). That class still references the original NekoHTML package org.cyberneko.html, but the 11.0 webapp only provides org.htmlunit:neko-htmlunit 4.21.0 (package org.htmlunit.cyberneko).

Steps to Reproduce

1. Install Confluence 11.0.0.
2. Install an app that injects ConfluenceWysiwygConverter (exported as an OSGi service) and calls convertXHtmlToWikiMarkup:

   @Bean
   public ConfluenceWysiwygConverter confluenceWysiwygConverter() {
       return importOsgiService(ConfluenceWysiwygConverter.class);
   }
   
   // in a class
   String wiki = converter.convertXHtmlToWikiMarkup("<p>Hello <strong>world</strong></p>", "");
   

3. Trigger the code

Expected Results

The XHTML is converted to wiki markup.

Actual Results

The request fails with HTTP 500.

The below exception is thrown in the atlassian-confluence.log file:

Caused by: java.lang.NoClassDefFoundError: org/cyberneko/html/parsers/DOMFragmentParser
	at com.atlassian.renderer.wysiwyg.converter.DefaultWysiwygConverter.convertXHtmlToWikiMarkup(DefaultWysiwygConverter.java:418)
	at com.atlassian.confluence.pages.wysiwyg.DefaultConfluenceWysiwygConverter.convertXHtmlToWikiMarkup(DefaultConfluenceWysiwygConverter.java:26)
	at com.atlassian.confluence.pages.wysiwyg.DefaultConfluenceWysiwygConverter.convertXHtmlToWikiMarkup(DefaultConfluenceWysiwygConverter.java:38)
	...
	at jdk.proxy4/jdk.proxy4.$Proxy431.convertXHtmlToWikiMarkup(Unknown Source)
	at com.atlassian.ecohelp.page.WikiServlet.doGet(WikiServlet.java:65)
	...
Caused by: java.lang.ClassNotFoundException: org.cyberneko.html.parsers.DOMFragmentParser

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available