Function postOrderExec

src/system-core.js:249–319

(loader, load, seen)

// returns a promise if and only if a top-level await subgraph
// throws on sync errors
function postOrderExec (loader, load, seen) {
  if (seen[load.id])
    return;
  seen[load.id] = true;

  if (!load.e) {
    if (load.er)
      throw load.er;
    if (load.E)
      return load.E;
    return;
  }

  // From here we're about to execute the load.
  // Because the execution may be async, we pop the `load.e` first.
  // So `load.e === null` always means the load has been executed or is executing.
  // To inspect the state:
  // - If `load.er` is truthy, the execution has threw or has been rejected;
  // - otherwise, either the `load.E` is a promise, means it's under async execution, or
  // - the `load.E` is null, means the load has completed the execution or has been async resolved.
  var exec = load.e;
  load.e = null;

  // deps execute first, unless circular
  var depLoadPromises;
  load.d.forEach(function (depLoad) {
    try {
      var depLoadPromise = postOrderExec(loader, depLoad, seen);
      if (depLoadPromise)
        (depLoadPromises = depLoadPromises || []).push(depLoadPromise);
    }
    catch (err) {
      load.er = err;
      if (!process.env.SYSTEM_PRODUCTION) triggerOnload(loader, load, err, false);
      throw err;
    }
  });
  if (depLoadPromises)
    return Promise.all(depLoadPromises).then(doExec);

  return doExec();

  function doExec () {
    try {
      var execPromise = exec.call(nullContext);
      if (execPromise) {
        execPromise = execPromise.then(function () {
          load.C = load.n;
          load.E = null; // indicates completion
          if (!process.env.SYSTEM_PRODUCTION) triggerOnload(loader, load, null, true);
        }, function (err) {
          load.er = err;
          load.E = null;
          if (!process.env.SYSTEM_PRODUCTION) triggerOnload(loader, load, err, true);
          throw err;
        });
        return load.E = execPromise;
      }