Sorry, should have clarified on 2. As an expansion of one of the examples given:

    loadAndPrintFile: (contents) {
       if (!contents) {
         fs.readFile() -> (error!, contents)
       }
       console.log(contents);
    }

i.e., expected behavior would be as if readFile was not an async function.

I'm asking because I built something similar (though it only worked with promises, not general async functions), and I'm curious to compare approaches :-) - mine is a sweet.js macro: http://pastie.org/9410315 (uses https://github.com/petkaantonov/bluebird and https://github.com/BranchMetrics/promise-accum). The basic syntax would be:

    task {
      item1 <- LoadItem(1);
      item2 <- LoadItem(item1.foreign_key);
      ret <- DoSomethingWithItems(item1, item2);
    }

The JavaScript result of your example looks like this:

(again, beautified because DesignToJS crams everything in one line to preserve the line numbers of your actual code):

  function loadAndPrintFile(contents) {
    if (!contents) {
      fs.readFile(function(error, contents){
        if(error !== null && error !== undefined){
          return error;
        }
      });
    }
    console.log(contents);
  }

If you omit the function body, it will only expand to the end of the current logical 'context' (or whatever it's called)

I'd suggest writing it like this in DesignToJS:

  loadAndPrintFile: (contents! console.log) {
    fs.readFile() -> (error!, contents! console.log)
  }

Result looks like this:

  function loadAndPrintFile(contents) {
      if(contents !== null && contents !== undefined){
          return console.log(contents);
      }
      fs.readFile(function(error, contents){
          if(error !== null && error !== undefined){
              return error;
          }
          if(contents !== null && contents !== undefined){
              return console.log(contents);
          }
      });
  }

Edit: I just submitted a patch that avoids unnecessary binding of 'this' if 'this' is not actually used.

In Javascript (contents !== null && contents !== undefined) is equivalent to (contents != null).

Now that is good to know, thank you. I'll make that change asap.

Ah, very interesting use of the ! operator.