Error Enhancement Suite
This little gem makes tracking errors in node.js more sane.
Consider the following contrived example:
var fs = require('fs')
getJsonFile('package.jsonn', function(err, data) {
if (err) return console.log(err.stack);
console.log(data);
});
function getJsonFile(filename, cb) {
getFile(filename, function(err, data) {
if (err) return cb(err);
var json = JSON.parse(data);
cb(null, json);
});
}
function _getFile(filename, cb) {
getFile(filename, cb);
}
function getFile(filename, cb) {
fs.readFile(filename, function(err, data) {
if (err) return cb(err);
cb(null, data);
});
}
Notice we spelled package.jsonn wrong, so when this code runs,
we get the following output:
Error: ENOENT, open 'package.jsonn'
If this were a large application running in production, that error would
be absolutely worthless.
Enter EES.
We can modify the previous example and just add some tagging and
inspections:
var fs = require('fs')
require('ees')
Error.category('caffeine');
getJsonFile('package.jsonn', function(err, data) {
if (err) return console.log(err.location('calling getJsonFile').report());
console.log(data);
});
function getJsonFile(filename, cb) {
_getFile(filename, function(err, data) {
if (err) return cb(err.location('getJsonFile'));
var json = JSON.parse(data);
cb(null, json);
});
}
function _getFile(filename, cb) {
getFile(filename, function(err, data) {
if (err) return cb(err
.location('_getFile')
.author('adam')
.caffeine(4)
.updated('2 Dec 2012')
);
cb(null, data);
});
}
function getFile(filename, cb) {
fs.readFile(filename, function(err, data) {
if (err) return cb(err
.location('calling fs.readFile')
.location('getFile')
.inspect('filename', filename)
.caffeine(7)
);
cb(null, data);
});
}
This generates a reverse stack trace and gives a report that looks like this:
location: calling fs.readFile
location: getFile
inspect: filename (string): 'package.jsonn'
caffeine: 7
location: _getFile
author: adam
caffeine: 4
updated: 2 Dec 2012
location: getJsonFile
location: calling getJsonFile
stack trace:
Error: ENOENT, open 'package.jsonn'
We can now tell what we were doing and the path that we took to get to
the erroneous code.
Magic.
