Typescript + schema should type check for whether field is required or optional.

[tianhuil]

Do you want to request a feature or report a bug?
Request a feature

What is the current behavior?
Consider the following example:

interface User {
  name: string;
  email: string;
  avatar?: string;
}

const schema = new Schema<User>({
  name: { type: String, required: true },
  email: { type: String, required: true },
  avatar: String
});

In the above, if avatar were required in the interface, the schema's non-required avatar would not throw a compile time error. Similarly, if name were optional in the interface, no error is reported from the schema's name being required. This appears to be expected (see docs):

You as the developer are responsible for ensuring that your document interface lines up with your Mongoose schema. For example, Mongoose won't report an error if email is required in your Mongoose schema but optional in your document interface.

What is the expected behavior?
I would like for the schema to type-check whether a field is required based on the interface. This is possible using typescript's typing system (e.g. Stackoverflow):

type MappedC<A, B> = {
  [K in keyof A & keyof B]:
  A[K] extends B[K]
    ? never
    : K
};

type OptionalKeys<T> = MappedC<T, Required<T>>[keyof T];

If there is interest, I'm happy to contribute a PR.

What are the versions of Node.js, Mongoose and MongoDB you are using? Note that "latest" is not a version.
This appears to be true for all versions of Mongoose and MongoDB.

[DavideViolante]

I think duplicate of #9715

[vkarpov15]

@tianhuil I'm not sure that would be entirely correct. For example, you could do:

interface User {
  name: string;
  email: string;
  avatar: string;
}

const schema = new Schema<User>({
  name: { type: String, required: true },
  email: { type: String, required: true },
  avatar: String
});

schema.path('avatar').required(true); // Make `avatar` required

That's perfectly valid, even though avatar is not required in the original schema definition. The issue comes down to the fact that the schema definition doesn't necessarily represent the complete state of the schema.

Another example: you can also make all string fields required by default using mongoose.SchemaTypes.String.set('required', true);, which would mean all strings are required even though you don't set required in the schema definition.

[tianhuil]

@vkarpov15: that's an interesting use case and not one that I would use.

Apparently the recommended solution is to use https://github.com/lstkz/ts-mongoose

Unfortunately, that project has not been updated since Nov. 2020.