As of v1.1.0-alpha1 (pre release package) the framework uses the VirtualPathProvider to access files rather than touching the physical file system.
The updated transformer can be seen below:
public class StyleRelativePathTransform
: IBundleTransform
{
public void Process(BundleContext context, BundleResponse response)
{
Regex pattern = new Regex(@"url\s*\(\s*([""']?)([^:)]+)\1\s*\)", RegexOptions.IgnoreCase);
response.Content = string.Empty;
// open each of the files
foreach (var file in response.Files)
{
using (var reader = new StreamReader(file.Open()))
{
var contents = reader.ReadToEnd();
// apply the RegEx to the file (to change relative paths)
var matches = pattern.Matches(contents);
if (matches.Count > 0)
{
var directoryPath = VirtualPathUtility.GetDirectory(file.VirtualPath);
foreach (Match match in matches)
{
// this is a path that is relative to the CSS file
var imageRelativePath = match.Groups[2].Value;
// get the image virtual path
var imageVirtualPath = VirtualPathUtility.Combine(directoryPath, imageRelativePath);
// convert the image virtual path to absolute
var quote = match.Groups[1].Value;
var replace = String.Format("url({0}{1}{0})", quote, VirtualPathUtility.ToAbsolute(imageVirtualPath));
contents = contents.Replace(match.Groups[0].Value, replace);
}
}
// copy the result into the response.
response.Content = String.Format("{0}\r\n{1}", response.Content, contents);
}
}
}
}