Error messaging

[jhoffner]

Currently when things such as syntax errors are thrown, a pretty confusing stack trace is returned. For example. Given the following user code:

function a(){

[stdin]:2
ESS__, output: $STDOUT};
    console._log(JSON.stringify(json));

} catch(ex){
                                                                    ^^^^^
SyntaxError: Unexpected token catch
    at Object. ([stdin]-wrapper:6:22)
    at Module._compile (module.js:456:26)
    at evalScript (node.js:532:25)
    at Socket. (node.js:154:11)
    at Socket.EventEmitter.emit (events.js:117:20)
    at _stream_readable.js:920:16
    at process._tickCallback (node.js:415:13)

I'm currently using a regexp to pull out the basic error message. So we get:
SyntaxError: Unexpected token catch

User thinks to himself: Catch? WTF? There is no catch in my code...

The problem stems from the fact that we are combining kata framework code along with the user submitted code. We need to wrap a try/catch around the user's solution so that if there are any errors, we can catch them and send them out as a JSON response.

So the above code gets turned into something along these lines:

try{
    function a(){ 

    console.log(JSON.stringify({success: true, output: []}))
}catch(ex){
  console.log(JSON.stringify({success: false, error: ex.message}))
}

This isn't an issue with the current system because there is no need to wrap the code, since the node runner uses a shovel script along with the built-in node sandbox. The shovel/shim does the wrapping for us, but it happens in a seperate file.

In the case of Ruby code, we actually pre-check the code before attempting to execute it using a Ruby parsing engine.

Ideally we can remedy this for all lanuages by using a format that is more natural to typical programming... using seperate files. In the case of JavaScript we could create a shim that does this:

try{
    var result = require './kata.js' 
    console.log(JSON.stringify(result))
}catch(ex){
  console.log(JSON.stringify({success: false, error: ex.message}))
}

The ruby version would look much the same.