cancel function caveats

catchErrors boolean and errorHandler function work Alright in most cases but there are edge cases as well which can cause the application to freeze or crash One of those cases is this, we have a simple GET route to /some_path and it has a middleware, which for some reason cancels the request by calling cancel function.

caution

The cancel function after running your callback and other necessary things, calls the res.end function to properly end the response cycle, however, res.end in itself is a response from server, after which we should not and cannot send another response back to the client. One more important thing to note here is that cancel DOES NOT halt code execution, it merely ends the request, So any code or logic set after calling cancel would still run.

When we call next function after calling cancel, it moves the execution forward to the next handler, which in this case is trying to send a response back to the user, and would fail, now if catchErrors value is true, the framework would detect this and pass this error to the errorHandler function, which in turns tries to send a response back to the client, which would crash the server even though the framework is claiming to catch all errors.

const Routine = require('routinejs')

const app = new Routine({
    enableBodyParsing: true,
    catchErrors: true,

    /**
     * To fix this, either remove `res.json` from below function or do not call `next` after calling `cancel`
     * in the middleware
     * */
    errorHandler: (error, req, res) => {
        res.json({
            message: error.stack,
        })
    },
})

function middleware(req, res, next, cancel) {
    cancel('Cancelled because of something', (req) =>
        console.log('request cancelled')
    )
    next()
}

app.get('/some_path', middleware, (req, res) => {
    res.json({
        message: req.params.name,
    })
})

app.listen(8080)