Why mongoose schema created with schema stored in variable won't see required flag?-CodePudding

If I store mongoose schema description object in the variable before creating new schema, it won't pick up proper schema options. For example:

const person = {
  name: { type: String, required: true }
};

const PersonSchema = new Schema(person);

type Person = InferSchemaType<typeof PersonSchema>;

Person type is now:

type Person = {
  name?: string;
}

Incorrectly marking name field as optional.

But when I do seemingly almost exact same thing:

const PersonSchema = new Schema({
  name: { type: String, required: true }
});

type Person = InferSchemaType<typeof PersonSchema>;

Person type is now:

type Person = {
  name: string;
}

Correctly having name marked as required.

I really have no idea why this is the case.

Anyone can explain? Thanks!

Codesandbox link: https://codesandbox.io/s/fancy-cdn-kx378p?file=/index.js

CodePudding user response：

I think I just answered myself after bit more fiddling around.

It's more of a typescript thing rather than mongoose.

It's basically happening because if I define my object like this:

const person = {
  name: { type: String, required: true }
};

The object is still mutable so typescript won't assume person.name is of any value and therefore name becomes string | undefined essentially making this prop optional.

The solution is to tell typescript compiler, that this object won't change by adding as const.

This will work fine:

const person = {
  name: { type: String, required: true }
} as const;

const PersonSchema = new Schema(person);

type Person = InferSchemaType<typeof PersonSchema>;

Results in:

type Person = {
  name: string;
}