Create a gist now

Instantly share code, notes, and snippets.

LESS CSS Support in System.Web.Optimization
public class LessTransform : IBundleTransform
{
public void Process(BundleContext context, BundleResponse bundle)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
if (bundle == null)
{
throw new ArgumentNullException("bundle");
}
context.HttpContext.Response.Cache.SetLastModifiedFromFileDependencies();
var lessParser = new Parser();
ILessEngine lessEngine = CreateLessEngine(lessParser);
var content = new StringBuilder(bundle.Content.Length);
var bundleFiles = new List<FileInfo>();
foreach (var bundleFile in bundle.Files)
{
bundleFiles.Add(bundleFile);
SetCurrentFilePath(lessParser, bundleFile.FullName);
string source = File.ReadAllText(bundleFile.FullName);
content.Append(lessEngine.TransformToCss(source, bundleFile.FullName));
content.AppendLine();
bundleFiles.AddRange(GetFileDependencies(lessParser));
}
if (BundleTable.EnableOptimizations)
{
// include imports in bundle files to register cache dependencies
bundle.Files = bundleFiles.Distinct();
}
bundle.ContentType = "text/css";
bundle.Content = content.ToString();
}
/// <summary>
/// Creates an instance of LESS engine.
/// </summary>
/// <param name="lessParser">The LESS parser.</param>
private ILessEngine CreateLessEngine(Parser lessParser)
{
var logger = new AspNetTraceLogger(LogLevel.Debug, new Http());
return new LessEngine(lessParser, logger, true, false);
}
/// <summary>
/// Gets the file dependencies (@imports) of the LESS file being parsed.
/// </summary>
/// <param name="lessParser">The LESS parser.</param>
/// <returns>An array of file references to the dependent file references.</returns>
private IEnumerable<FileInfo> GetFileDependencies(Parser lessParser)
{
IPathResolver pathResolver = GetPathResolver(lessParser);
foreach (var importPath in lessParser.Importer.Imports)
{
yield return new FileInfo(pathResolver.GetFullPath(importPath));
}
lessParser.Importer.Imports.Clear();
}
/// <summary>
/// Returns an <see cref="IPathResolver"/> instance used by the specified LESS lessParser.
/// </summary>
/// <param name="lessParser">The LESS parser.</param>
private IPathResolver GetPathResolver(Parser lessParser)
{
var importer = lessParser.Importer as Importer;
var fileReader = importer.FileReader as FileReader;
return fileReader.PathResolver;
}
/// <summary>
/// Informs the LESS parser about the path to the currently processed file.
/// This is done by using a custom <see cref="IPathResolver"/> implementation.
/// </summary>
/// <param name="lessParser">The LESS parser.</param>
/// <param name="currentFilePath">The path to the currently processed file.</param>
private void SetCurrentFilePath(Parser lessParser, string currentFilePath)
{
var importer = lessParser.Importer as Importer;
if (importer == null)
throw new InvalidOperationException("Unexpected dotless importer type.");
var fileReader = importer.FileReader as FileReader;
if (fileReader == null || !(fileReader.PathResolver is ImportedFilePathResolver))
{
fileReader = new FileReader(new ImportedFilePathResolver(currentFilePath));
importer.FileReader = fileReader;
}
}
}
public class ImportedFilePathResolver : IPathResolver
{
private string currentFileDirectory;
private string currentFilePath;
public ImportedFilePathResolver(string currentFilePath)
{
if (string.IsNullOrEmpty(currentFilePath))
{
throw new ArgumentNullException("currentFilePath");
}
CurrentFilePath = currentFilePath;
}
/// <summary>
/// Gets or sets the path to the currently processed file.
/// </summary>
public string CurrentFilePath
{
get { return currentFilePath; }
set
{
currentFilePath = value;
currentFileDirectory = Path.GetDirectoryName(value);
}
}
/// <summary>
/// Returns the absolute path for the specified improted file path.
/// </summary>
/// <param name="filePath">The imported file path.</param>
public string GetFullPath(string filePath)
{
if (filePath.StartsWith("~"))
{
filePath = VirtualPathUtility.ToAbsolute(filePath);
}
if (filePath.StartsWith("/"))
{
filePath = HostingEnvironment.MapPath(filePath);
}
else if (!Path.IsPathRooted(filePath))
{
filePath = Path.GetFullPath(Path.Combine(currentFileDirectory, filePath));
}
return filePath;
}
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment