Mongoose model become undefined when exported

Question

I export the model DemandeTransports from this file:

//@/components/database/model/Schema.js
import { Schema } from "mongoose";
import mongoose from "mongoose";

const userSchema = new Schema({
  email: { type: String, index: true, unique: true, required: true },
  password: { type: String, required: true },
  role: { type: String, required: true },
  infos: Map,
});

const Users = mongoose.models?.user || new mongoose.model("user", userSchema);

const demandeTransportSchema = new Schema({
  date: { type: Date, required: true },
  user: { type: Object, required: true },
  values: { type: Object, required: true },
});

const DemandeTransports =
  mongoose.models?.demandeTransport ||
  new mongoose.model("demandeTransport", demandeTransportSchema);

console.log(DemandeTransports.findOne);
export { Users, DemandeTransports };

Which log (on server): [Function: findOne]

But when I try to import the model in this file:

//@/lib/getAllDemandesFromUser.js
import connectMongo from "@/components/database/conn";
import { DemandeTransports } from "@/components/database/model/Schema";

export default function getAllDemandesFromUser(email) {
  console.log("JSON.stringify(DemandeTransports)");
  console.log(JSON.stringify(DemandeTransports));
  connectMongo().catch((error) =>
    res.status(500).json({
      error: "La connection à la bdd mongo a échoué avec l'erreur : " + error,
    })
  );
  const result = DemandeTransports.findOne({ "user.email": email });
  return result;
}

I get TypeError: components_database_model_Schema__WEBPACK_IMPORTED_MODULE_1 _.DemandeTransports.findOne is not a function

And DemandeTransports is logged as undefined, and I can't figure out why.

Answer 1

I just understood: My basis error was that I tried to connect to the mongodb while being in client side, which is impossible. I transfered all my call to the db in a getServerSideProps function:

export async function getServerSideProps(context) {
  const session = await unstable_getServerSession(
    context.req,
    context.res,
    authOptions
  );
  // Fetch data from external API
  connectMongo().catch((error) =>
    console.log("Erreur lors de la connection à la bdd : " + error)
  );
  const result = await DemandeTransports.findOne({
    "user.email": session.user.email,
  });

  const result2 = result.toObject();
  console.log(result.toObject());
  // Pass data to the page via props
  return { props: { result2 } };
}

And now it works perfectly fine.