We chased a fun bug in the afternoon after we deployed our new package to our staging server.

Symptom:

Our customized Content Query Web Parts stops rendering.
But we noticed they were still functioning when we drop into edit mode.

Hint:

This gave us the hint that our XSL was probably stuffed – but it checked out ok in SharePoint designer*.

Detective Work:

Digging through the SharePoint logs, we came across two lines that are incredibly suspicious:

0x17C4    Windows SharePoint Services       Web Parts                         89a1    Monitorable    Error while executing web part: System.Xml.Xsl.XslLoadException: XSLT compile error. An error occurred at (1,482). ---> System.Net.WebException: The remote server returned an error: (401) Unauthorized.     at System.Net.HttpWebRequest.GetResponse()     at System.Xml.XmlDownloadManager.GetNonFileStream(Uri uri, ICredentials credentials)     at System.Xml.XmlDownloadManager.GetStream(Uri uri, ICredentials credentials)     at System.Xml.XmlUrlResolver.GetEntity(Uri absoluteUri, String role, Type ofObjectToReturn)     at Microsoft.SharePoint.WebPartPages.WSSXmlUrlResolver.GetEntity(Uri absoluteUri, String role, Type ofObjectToReturn)     at System.Xml.Xsl.Xslt.XsltLoader.CreateReader(Uri uri, XmlResolver xmlResolver)     at System.Xml.Xsl.Xslt.XsltLoader.LoadStylesheet(Uri uri, Boolean include...    

0x17C4    Windows SharePoint Services       General                           72ks    Medium      Cannot get ghost document:

Features\blah\blah.xsl    

Story:

The path to the XSL was familiar, and the problem immediately became apparent.  It was the old path, we’ve since re-organized our deployment package, and that old path to the xsl file no longer works.

The Fix:

Drop into Style Library\ and delete all the XSL files that are ghosted.
Deactivate and reactivate the XSL feature so they get re-ghosted.

Notes:

SharePoint designer must have cached the file at some point, so it was happily showing us a copy of the file while in reality due to our re-organization of the feature it wasn’t actually available anymore.

Re-organizing feature package always has hidden costs…