mongoose with rxjs - can´t catch error on promise resolve - node.js

Question

i´m using mongoose in my node.js - express. In my schema model i´m using the package mongoose-unique-validator to check that user email is unique, if the email already exist i would get and error ValidationError: User validation failed: email: Error, expected "email" to be unique. Value: "example#example.com" (which is fine). i decide to turn my promises from mongoose to rxjs observables this way:
controller.ts
creatUser(req: Request, res: Response, next: NextFunction) {
from(bcrypt.hash(req.body.password, 10))
.pipe(
mergeMap((hash) => {
const avatartPath = this.utilities.generateImgPath(req);
const user = this.userAdatper.userAdatper(req.body, { password: hash, avatar: avatartPath });
return of(new User(user).save()).pipe(catchError((error) => of(error)));
})
)
.subscribe(
(user) => {
console.log() // Promise is resolve here on the validation error return an empty object
res.status(201).send(user);
},
(err) => {
console.log(err);
res.status(500);
const error = new Error(`Internal Server Error - ${req.originalUrl}`);
next(error);
}
);
}
**Schema**
const UserSchema = new Schema({
user_rol: {
type: String,
default: 'subscriber',
},
firstName: {
type: String,
required: true,
},
lastName: {
type: String,
requiered: true,
},
fullName: {
type: String,
requiered: true,
},
email: {
type: String,
requiered: true,
unique: true,
},
password: {
type: String,
requiered: true,
},
avatar: {
type: String,
requiered: true,
},
favorites: [
{
type: [Schema.Types.ObjectId],
ref: 'ArcadeItems',
},
],
updatedOn: {
type: Date,
required: true,
},
created: {
type: Date,
default: Date.now,
},
});
UserSchema.plugin(uniqueValidator);
but for some reason if the promise fail, it resolve on the success callback after subscription returning and empty object and no the error callback, try to implement catchError() from rxjs operators but no success.

Answer 1

Replace of(new User(user)...) for from(new User(user)...) and on cathError() return throwError(error)
creatUser(req: Request, res: Response, next: NextFunction) {
from(bcrypt.hash(req.body.password, 10))
.pipe(
mergeMap((hash) => {
const avatartPath = this.utilities.generateImgPath(req);
const user = this.userAdatper.userAdatper(req.body, { password: hash, avatar: avatartPath });
return from(new User(user).save()).pipe(catchError((error) => throwError(error)));
})
)
.subscribe(
(user) => {
console.log() // Promise is resolve here on the validation error return an empty object
res.status(201).send(user);
},
(err) => {
console.log(err);
res.status(500);
const error = new Error(`Internal Server Error - ${req.originalUrl}`);
next(error);
}
);
}