coffee-backtrace

Expands coffee files in uncaught exceptions to add context with the compiled Javascript

npm install coffee-backtrace
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coffee-backtrace

A Node.js module for servers written in CoffeeScript to aide in debugging uncaught exceptions.

Note: This package is somewhat redundant with CoffeeScript 1.6.2. CoffeeScript will now show you the correct line number of the exception within the coffee file. However, CoffeeScript currently only performs this expansion on the file executed with the command and not on any other required file. See pull request 2968 for possible information regarding this being available on all files.

What it does

When an exception is thrown, unfortunately the error message and corresponding line number can be cryptic, as they correspond to what happened in the compiled JavaScript file, and not the source CoffeeScript file. This aims to reduce the pain of debugging by finding the offending line and providing some context as well. See some example output from the provided example file:

$ coffee example.coffee

TypeError: Object [object Object] has no method 'getMessage'
 at [object Object].Relay.speak [as _onTimeout] (/home/doug/dev/coffee-backtrace/example.coffee:12:40)
         }

         Relay.prototype.speak = function() {
>          return process.stdout.write(this.getMessage() + '\n');
         };

         Relay.prototype.getMessage = function() {
 at Timer.listOnTimeout [as ontimeout] (timers.js:110:15)

Of course, if you are using a terminal, the error is color-coded red to help it stand out more. The > are added so that the message is still able to be read in a log file.

How to use

  1. Add to your package.json dependencies and run npm install or run npm install coffee-backtrace.

  2. In your entry point file, add the following:

     require('coffee-backtrace')
    
  3. That's it.

Note that if you are also using the coffee-script package in your application, be sure to require() it before coffee-backtrace, or else it will override the stack trace hooks.

Extra configuration

You can control the number of context lines shown in one of two ways:

  1. Start the process with the COFFEE_BACKTRACE_CONTEXT variable set:

     $ COFFEE_BACKTRACE_CONTEXT=10 coffee app.coffee
    
  2. Use the setContext method on the required module:

     require('coffee-backtrace').setContext(0)
    
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