systemjs/lib/extension-meta.js

System loader extension for flexible AMD & CommonJS support

/*
 * Meta Extension
 *
 * Sets default metadata on a load record (load.metadata) from
 * loader.meta[moduleName].
 * Also provides an inline meta syntax for module meta in source.
 *
 * Eg:
 *
 * loader.meta['my/module'] = { some: 'meta' };
 *
 * load.metadata.some = 'meta' will now be set on the load record.
 *
 * The same meta could be set with a my/module.js file containing:
 * 
 * my/module.js
 *   "some meta"; 
 *   "another meta";
 *   console.log('this is my/module');
 *
 * The benefit of inline meta is that coniguration doesn't need
 * to be known in advance, which is useful for modularising
 * configuration and avoiding the need for configuration injection.
 *
 *
 * Example
 * -------
 *
 * The simplest meta example is setting the module format:
 *
 * System.meta['my/module'] = { format: 'amd' };
 *
 * or inside 'my/module.js':
 *
 * "format amd";
 * define(...);
 * 
 */

function meta(loader) {
  var metaRegEx = /^(\s*\/\*.*\*\/|\s*\/\/[^\n]*|\s*"[^"]+"\s*;?|\s*'[^']+'\s*;?)+/;
  var metaPartRegEx = /\/\*.*\*\/|\/\/[^\n]*|"[^"]+"\s*;?|'[^']+'\s*;?/g;

  loader.meta = {};

  function setConfigMeta(loader, load) {
    var meta = loader.meta && loader.meta[load.name];
    if (meta) {
      for (var p in meta)
        load.metadata[p] = load.metadata[p] || meta[p];
    }
  }

  var loaderLocate = loader.locate;
  loader.locate = function(load) {
    setConfigMeta(this, load);
    return loaderLocate.call(this, load);
  }

  var loaderTranslate = loader.translate;
  loader.translate = function(load) {
    // detect any meta header syntax
    var meta = load.source.match(metaRegEx);
    if (meta) {
      var metaParts = meta[0].match(metaPartRegEx);
      for (var i = 0; i < metaParts.length; i++) {
        var len = metaParts[i].length;

        var firstChar = metaParts[i].substr(0, 1);
        if (metaParts[i].substr(len - 1, 1) == ';')
          len--;
      
        if (firstChar != '"' && firstChar != "'")
          continue;

        var metaString = metaParts[i].substr(1, metaParts[i].length - 3);

        var metaName = metaString.substr(0, metaString.indexOf(' '));
        if (metaName) {
          var metaValue = metaString.substr(metaName.length + 1, metaString.length - metaName.length - 1);

          if (load.metadata[metaName] instanceof Array)
            load.metadata[metaName].push(metaValue);
          else if (!load.metadata[metaName])
            load.metadata[metaName] = metaValue;
        }
      }
    }
    // config meta overrides
    setConfigMeta(this, load);
    
    return loaderTranslate.call(this, load);
  }
}