Hapi error: handler method did not return a value, a promise, or thrown an error

Question

I have a NodeJS application using Hapi on version 17 which consumes a web service which returns an image of a map, however, when run the code below I get the following error:

Debug: internal, implementation, error
    Error: handler method did not return a value, a promise, or throw an error
    at module.exports.internals.Manager.execute (C:\map\node_modules\hapi\lib\toolkit.js:52:29)
    at <anonymous>
    at process._tickCallback (internal/process/next_tick.js:188:7)

---

var Hapi = require('hapi'),
server = new Hapi.Server({
    host: '0.0.0.0',
    port: 8080,
    routes: {
        cors: true
    },
    SphericalMercator = require('sphericalmercator'),
    sm = new SphericalMercator({ size: 256 }),
    prequest = require('request').defaults({ encoding = null });

var wmsUrl = "http://localhost:8088/service/wms?SERVICE=WMS&REQUEST=GetMap&VERSION=1.1.1&STYLES=&FORMAT=image%2Fpng&HEIGHT=383&WIDTH=768&SRS=EPSG%3A3857";

server.route({
    method: 'GET',
    path: '/{layers}/{z}/{x}/{y}.png',
    handler: async (request, h) => {
        var bbox = sm.bbox(request.params., request.params.y, request.params.z, false, '00000');
        var theUrl = `${wmsUrl}&BBOX=${bbox.join(',')}&LAYERS=${decodeURIComponent(request.params.layers)}`;
        prequest.get(theUrl, function (err, res, body) {
            h.response(body).header('Cache-Control'), 'public, max-age=2629000').header('Content-Type', 'image/png');
        });
    }
});

server.start();

What am I doing wrong?

I'm writing this in the phone as the PC I'm working with right now, has no internet access, if I missed something or misspelled anything because of auto corrector, feel free to point it and I'll edit it to correct it.

Answer 1

If you look at the hapi docs for lifecycle methods it states:

Each lifecycle method must return a value or a promise that resolves into a value.

So, just return something in your handler:

 handler: async (request, h) => {
        var bbox = sm.bbox(request.params., request.params.y, request.params.z, false, '00000');
        var theUrl = `${wmsUrl}&BBOX=${bbox.join(',')}&LAYERS=${decodeURIComponent(request.params.layers)}`;
        prequest.get(theUrl, function (err, res, body) {
            h.response(body).header('Cache-Control'), 'public, max-age=2629000').header('Content-Type', 'image/png');
        });

        return null; // or a Plain Value: string, number, boolean. Could be a Promise etc, more on the link above.
    }

If you don't return anything it would be undefined which it doesn't like.

EDIT:

If you want to return the body result from prequest, you can wrap it in a Promise and return it:

handler: async (request, h) => {
    ...

    const promise = new Promise((resolve, reject) => {
        prequest.get(theUrl, function (err, res, body) {
            if (err) {
                reject(err);
            } else {
                const response = h.response(body)
                    .header('Cache-Control', 'public, max-age=2629000')
                    .header('Content-Type', 'image/png');

                resolve(response);
            }

        });
    });

    return promise;
}