Cannot overwrite `User` model once compiled. When resolved i get 'User' Undefined - node.js

Question

I'm currently working on the backend of a shopping website,
while working on my post functions. I get this error
"OverwriteModelError: Cannot overwrite User model once compiled."
Everything works fine until when i go for the buy character where it needs a search query for both the User and Character and pushing the character into the array ownedCharacter in the User model.
when i remove the const User = require('../Model/User'); and test the function buy character in postman it says that the User is Undefined.
Here's the code for the model
const mongoose = require('mongoose');
const UserSchema = new mongoose.Schema({
username:{
type: String,
required : true
},
email:{
type: String,
required: true
},
password:{
type: String,
required: true,
min: 8
},
status:{
type:Boolean,
default:false
},
points:{
type:Number,
default: 0
},
rank:{
type:String,
default:"unranked"
},
avatar:{
type:String,
default:""
},
level:{
type:Number,
default:0
},
experience:{
type:Number,
default:0
},
registrationDate:{
type:Date,
default:Date.now()
},
gold:{
type:Number,
default:0
},
gems:{
type:Number,
default:0
},
ownedCharacter:[{
type:mongoose.Schema.Types.ObjectId,
ref:"Character",
}],
},{timestamps:true});
module.exports = mongoose.model("User", UserSchema);
Here's the code for the app.js
const express = require('express');
const app = express();
const mongoose = require('mongoose');
const dotenv = require('dotenv');
const bodyParser = require("body-parser");
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({
extended: true
}));
app.use(express.static('uploads'));
//Import Routes
const authRoute = require ('./Route/Auth');
const authAdminRoute = require ('./Route/Admin_Auth');
const shopRoute = require('./Route/Shop');
dotenv.config();
//Connection to DataBase
mongoose.connect(
process.env.DB_CONNECT,
{useNewUrlParser: true, useUnifiedTopology: true},
()=>console.log('connected to database')
);
//MiddleWares
app.use(express.json());
//Route MiddleWares
app.use('/api/user', authRoute);
app.use('/api/admin', authAdminRoute);
app.use('/api/shop',shopRoute);
//Server Listener
app.listen(27017, ()=> console.log("Server Running"));
and here's the shop route
const router = require('express').Router();
const User = require('../Model/User');
const Character = require('../Model/Character');
const Skin = require('../Model/Skin');
//admin add character
router.post('/addCharacter', async (req, res) =>{
const character = new Character({
name:req.body.name,
price:req.body.price,
story:req.body.story,
ability:{
abilityName:req.body.abilityName,
cooldown:req.body.cooldown,
description:req.body.description
},
});
try {
const savedCharacter = await character.save();
res.json({savedCharacter});
console.log(character);
} catch (error) {
}
});
//add Skin
router.post('/addSkin/:characterId', async (req, res) =>{
const skin = new Skin({
name:req.body.name,
price:req.body.price,
description:req.body.description,
characterId: req.params.characterId
});
try {
const savedSkin = await skin.save();
res.json({skin});
console.log(skin);
} catch (error) {
}
});
//add Monsters
router.post('/addMonster/', async (req, res) =>{
const mosnter = new Monster({
name:req.body.name,
price:req.body.price,
description:req.body.description,
});
try {
const savedMonster = await monster.save();
res.json({monster});
console.log(monster);
} catch (error) {
}
});
//add Traps
router.post('/addTrap', async (req, res) =>{
const trap = new Trap({
name:req.body.name,
price:req.body.price,
description:req.body.description,
});
try {
const savedTrap = await trap.save();
res.json({trap});
console.log(trap);
} catch (error) {
}
});
//buy a Character
router.post('/buyCharacter/:characterId/:userId',async(req,res)=>{
try {
const user = await User.findOne({_id:req.params.userId});
console.log("user:"+user);
const boughtCharacter = await Character.findOne({_id:req.params.characterId});
user.ownedCharacter.push(boughtCharacter);
user.save();
res.json(boughtCharacter);
console.log(boughtCharacter);
} catch (error) {
console.log(error.message);
}
});
module.exports = router;

Answer 1

Is the casing correctly matched between your require statements and the file names? If the filename is actually /Model/user.js, it could throw this error.

Answer 2

The error message is telling you that somehow, you are declaring a model named User more than once. Unless you are explicitly doing so again in another file, you're best bet is that the User.js file is being loaded twice. There are a few reasons why that can happen, but the most likely cause is that you are importing the ../Model/User.js file in multiple places, but your casing is inconsistent.
When Node loads an import, it caches it using the resolved filename you pass to require()... and it does so in a case-sensitive manner. What that means is that if you have require(../Model/user) in one file and require(../Model/User) in
another, Node will load the same file twice, thus executing the file twice, thus attempting to set a model named User on the shared mongoose instance twice, and thus giving you the OverwriteModelError you are experiencing.
I'd do a find in your IDE and look at everywhere you are requiring that model.