fs.createReadStream Should Be Re-engineered

I just had a strange WTF moment with node.

To avoid the state of dismay I went in, just remember this:

In node, streams have a on('error', function(err) {}) method which they run when some errors happen. Usually, node’s default APIs hook a callback to the error, and give you information about this error in the continuation, like so:

fs.readFile(file, function(err, data) { /* you have access to err here */ });

Unfortunately, fs.createReadStream doesn’t work like that. Since there is no listener for the ‘error’ event on the stream, node crashes loudly, and you cannot try/catch that, because it doesn’t happen in the same event loop cycle as the call.

try {
 var stream = fs.createReadStream('./bogus-file');
} catch (e) {
 // Not caught!

My advice: if a stream doesn’t give you error information, listen to its ‘error’s.

stream.on('error', function(err) { ... });

I caught the issue as I read the source code of stream.js.

// don't leave dangling pipes when there are errors.
function onerror(er) {
  if (this.listeners('error').length === 0) {
    throw er; // Unhandled stream error in pipe.

If nothing listens to the ‘error’ event, it crashes. Obviously, this kind of construct fails to work with try/catch.

As a result, I wish all node API calls used the usual node error handling.

fs.createReadStream(file, function (err) { ... }, options);

Why wasn’t it designed this way originally?

APIs are hard. At least they’re not copyrightable now.