問題描述：

修改gulp-rev-append外掛實現自動修改檔案中靜態資源連結新增md5版本號。但是前天有一點點很遺憾，對CSS中background:url()的匹配還存在一點點不足，url()必須帶單引號或者雙引號才能被正確匹配的到，但是CSS的標準寫法中，通常不會帶單引號或者雙引號。

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解決方案：

var FILE_DECL = /(?:href=|src=|url\()(?:['|"]?)([^\s>']+?)\?v=(@@hash).+(?:['|"|>]?)/gi;

具體完整程式碼：

var fs = require('fs');
var path = require('path');
var crypto = require('crypto');
var Buffer = require('buffer').Buffer;
var gutil = require('gulp-util');
var PluginError = gutil.PluginError;
var map = require('event-stream').map;

// var FILE_DECL = /(?:href=|src=|url\()['|"]([^\s>"']+?)\?v=([^\s>"']+?)['|"]/gi;
var FILE_DECL = /(?:href=|src=|url\()(?:['|"]?)([^\s>']+?)\?v=(@@hash).+(?:['|"|>]?)/gi;

var revPlugin = function revPlugin() {

  return map(function(file, cb) {

    var contents;
    var lines;
    var i, length;
    var line;
    var groups;
    var dependencyPath;
    var data, hash;

    if(!file) {
      throw new PluginError('gulp-rev-append', 'Missing file option for gulp-rev-append.');
    }

    if(!file.contents) {
      throw new PluginError('gulp-rev-append', 'Missing file.contents required for modifying files using gulp-rev-append.');
    }

    contents = file.contents.toString();
    lines = contents.split('\n');
    length = lines.length;

    for(i = 0; i < length; i++) {
      line = lines[i];
      groups = FILE_DECL.exec(line);
      if(groups && groups.length > 1) {
        var normPath = path.normalize(groups[1]);
        if (normPath.indexOf(path.sep) === 0) {
          dependencyPath = path.join(file.base, normPath);
        }
        else {
          dependencyPath = path.resolve(path.dirname(file.path), normPath);
        }

        try {
          data = fs.readFileSync(dependencyPath);
          hash = crypto.createHash('md5');
          hash.update(data.toString(), 'utf8');
           
          line = line.replace(groups[2], hash.digest('hex'));
        }
        catch(e) {
          // fail silently.
        }
      }
      lines[i] = line;
      FILE_DECL.lastIndex = 0;
    }

    file.contents = new Buffer(lines.join('\n'));
    cb(null, file);

  });

};

module.exports = revPlugin;