Error Handling in express on async functions does not work-CodePudding

I've been trying to implement Error Handling in Express on async functions with try and catch as well as creating a separate file but when I get the error express doesn't handle it, the site just crashes.

I have tested it on app.get('/campgrounds/:id... I would connect to a fake id to see if the error handler catches it but it doesn't.

The JS file:

const express = require('express');
const path = require('path');
const mongoose = require('mongoose');
const Campground = require('./modules/campground');
const engine = require('ejs-mate');
const methodOverride = require('method-override');
const cities =  require('./seeds/cities')
const ExpressError = require('./utilities/ExpressError');
const catchAsync = require('./utilities/catchAsync');

mongoose.connect('mongodb://localhost:27017/yelpcamp');

const db = mongoose.connection;
db.on("error", console.error.bind(console, "connection error:"));
db.once("open", () => {
    console.log("Database connected");
});

const app = express();

app.engine('ejs', engine);
app.set('view engine','ejs');
app.set('views',path.join(__dirname,'views'));
app.use(express.urlencoded({extended:true}));
app.use(methodOverride('_method'));


app.get('/',(req,res)=>{
 res.redirect('/campgrounds');
})

app.get('/campgrounds',catchAsync(async (req,res)=>{
    const campgrounds = await Campground.find({});
    res.render('campgrounds/index',{campgrounds})
}))

app.get('/campgrounds/new',catchAsync(async (req,res)=>{
    const campgrounds = await Campground.find({});
    res.render('campgrounds/new',{ campgrounds })   
}))
app.post('/campgrounds',catchAsync(async(req,res, next)=>{
    const newCampground = new Campground(req.body);
    await newCampground.save();
    res.redirect(`campgrounds/${newCampground._id}`);
}))  
app.patch('/campgrounds/:id', catchAsync(async (req,res)=>{
    const {id}=req.params;
    const campground = await Campground.findByIdAndUpdate(id, req.body, {runValidators: true, new: true});
    res.redirect(`/campgrounds/${id}`)
}))

app.delete('/campgrounds/:id',catchAsync(async (req,res)=>{
    const { id } = req.params;
    await Campground.findByIdAndDelete(id);
    res.redirect('/campgrounds');
}))
app.get('/campgrounds/:id',catchAsync(async (req,res,next)=>{
    const { id } = req.params;
    const campground = await Campground.findById(id);
    res.render('campgrounds/details',{campground})
}))
app.get('/campgrounds/:id/edit',catchAsync(async(req,res)=>{
    const { id } = req.params;
    const campgrounds = await Campground.find({});
    const campground = await Campground.findById(id);
    res.render('campgrounds/edit',{campground, campgrounds});
}))
app.use((err,req,res,next)=>{
    res.send('Error here!');
})

app.listen(3000,()=>{
    console.log('Listening on port 3000')    
})

This is the separate file called catchAsync:

module.exports = func =>{
    return (req,res,next) =>{
        func(req,res,next).catch(next);
    }
}

CodePudding user response：

Mongoose returns null if it does not find a document using findById. So in your case const campground = await Campground.findById(id); does not throw an error/rejects, instead null is passed as campground to your ejs-template, which probably results in the error you've described.

If you want to actually throw an error and force your error-handler to be invoked, you can throw an error from your /find-handler, e.g.

app.get('/campgrounds/:id',catchAsync(async (req,res,next)=>{
    const { id } = req.params;
    const campground = await Campground.findById(id);
    if(!campground) {
      throw new Error("Campground not found");
    }
    res.render('campgrounds/details',{campground})
}))