hapi-onpreresponse.js

const Hapi = require('hapi');

const server = new Hapi.Server();
server.connection({port: 3000});

server.register(require('vision'), (err) => {

    if (err) {
        throw err;
    }

    server.views({
        engines: { jade: require('jade') },
        path: __dirname,
        compileOptions: {
            pretty: true
        }
    });
});

server.route({
    method: 'GET',
    path: '/',
    handler: function(requst, reply) {
        throw new Error;
    }
})


server.ext('onPreResponse', function (request, reply) {
    if (request.response.isBoom) {
        return reply.view('template', {
            message: 'Boom!'
        })
    }
    reply.continue();
})

server.ext('onPreResponse', function (request, reply) {
    console.log("I am never called");
    // do something with template context
    request.response.source.context.message2 = 'Everything is fine';
    reply.continue();
})

server.start((err) => {
    if (err) {
        throw err;
    }
    console.log('Server running at:', server.info.uri);
})

package.json

{
  "name": "hapi-onpreresponse-issue",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "dependencies": {
    "hapi": "^13.0.0",
    "jade": "^1.11.0",
    "vision": "^4.0.1"
  },
  "devDependencies": {},
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC"
}

template.jade

div Message: #{message}
div Message2: #{message2}