Simple apply-loader module for webpack, published @ https://www.npmjs.com/package/apply-loader

index.js

var loaderUtils = require('loader-utils');

module.exports = function(source) {
  this.cacheable && this.cacheable();
  var query = loaderUtils.parseQuery(this.query);
  var args = [];

  // apply?config=key => sourceFn(require('webpack.config').key)
  if (typeof query.config === 'string') {
    if (!query.config in this.options)
      throw new Error("apply-loader: '"+query.config+"' property not present in webpack config");
    args.push(this.options[query.config]);
  }

  // apply?obj={a: 1, b:2} => sourceFn({a: 1, b:2})
  if (query.obj)
    args.push(query.obj);

  // apply?args[]=1&args[]=2 => sourceFn(1, 2)
  if (Array.isArray(query.args))
    args.push.apply(args, query.args);

  source += "\n\nmodule.exports = module.exports.apply(module, "
        +  JSON.stringify(args)
        +  ")";
  return source;
};

package.json

{
  "name": "apply-loader",
  "version": "0.1.0",
  "description": "Apply loader for webpack",
  "main": "index.js",
  "scripts": {
  },
  "author": "Victor Hallberg <[email protected]>",
  "license": "MIT",
  "dependencies": {
    "loader-utils": "~0.2.6"
  },
  "keywords": [
    "webpack",
    "loader",
    "apply"
  ]
}

And please change comment apply?obj={a: 1, b:2} to apply?{obj: {a: 1, b:2}}. Because the first one doesn't working. (According to documentation of loaderUtils)

Thanks for the feedback Kreozot! I changed the comment and published the package to npm:
https://www.npmjs.com/package/apply-loader