Route param error handle

[cosmosgenius]

var webapps = express.Router();
module.exports = webapps;

function handleError(err, req, res, next) {
    //this function is not executed
    res.send("hello");
    next();
}

webapps.param("app", function(req, res, next, name) {
    next("asfaf");
});

webapps.route("/:app")
    .all(handleError);

I am expected handleError to be executed and send a response of "hello", but instead "asfaf" is being send with status 500.

[dougwilson]

Ah, it's because the error handler is within the route and since the error is the parameter, the route is not actually entered.

I agree though, that it would make sense to execute error handlers within the route if there was an error in a parameter for the route.

[cosmosgenius]

So if we have to catch this type of error it has to be on top of the router?

[dougwilson]

Yes, it has to be on the router, after your route. You can also add a second route with the same path that does not use the same parameter to try and only capture the correct error.

This change would be a pretty big behavior change, so it'll likely have to wait for 5.0, which is due this month sometime after the io.js release.

[dougwilson]

I'll put this in the router module though, so you can use that in any version of express, so you don't have to wait.

[scottcorgan]

So does this remove the error middleware with 4 params?

[dougwilson]

No. This is to make it possible to catch errors from app.param(name, fn) functions within the route itself.