Remove Joi from types

[kanongil]

This PR removes the explicit import of Joi in the typings. As it is, any typescript users that use Hapi, will need to add a dependency of Joi, just to resolve the typings.

The explicit dependency is replaced by a generic validator that can be set on the Server object, or inferred from the config. This has the additional advantage, that other validators will be able to be typed instead of assuming that Joi is used.

The new types will require a bit of work to adapt to for projects that use server.validate().

This fixes #4491.

Definition

const MySimpleValidator = {
    compile(schema: MySchema) {

        return {
            validate(value: unknown, options: MyOptions & { context?: Validation.Context }) {

                return { value: 'everything is awesome' };
            }
        };
    }
};

The base Joi object already implement this interface.

Registration

Explicit:

const server = new Server<ServerApplicationState, typeof Joi>({});
server.validator(Joi);

Inferred from config:

const server = new Server({
    routes: { validate: { validator: Joi } }
});

Using the new validator() returned value:

const server = new Server({})
    .validator(Joi);

For plugins

Explicit:

register(server: Server<unknown, typeof Joi>, options: any) {

    server.validator(Joi);
    …
}

Using the new validator() returned value:

register(_server: Server, options: any) {

    const server = _server.validator(Joi);
    …
}

Usage

Once registered, the validator typings are used to help type the validation options:

server.route({
    …,
    options: {
        validate: {
            options: {
                // Validated against the options that can be passed to the registered `validate()` method
            },
            query: {
                // Validated against the type of the `schema´ from the registered `compile()` method
            }
        }
    }
});

It can be overriden at the route level:

server.route({
    …,
    options: {
        validate: {
            validator: Joi,   // Route-only validator
            options: {
                // Validated against the options that can be passed to the validator `validate()` method
            },
            query: {
                // Validated against the type of the `schema´ from the validator `compile()` method
            }
        }
    }
});

It also allows custom inline validators:

server.route({
    …,
    options: {
        validate: {
            query: (value, optionsAndContext) {

                // optionsAndContext is typed with the `context` object
            }
        }
    }
});

It is also used to validate rules:

server.rules(processor, {
    validate: {
        schema: validateSchema,    // Validated against the type of the `schema´ from the registered `compile()` method
        options: {
            // Validated against the options that can be passed to the registered `validate()` method
        }
    }
});

As it currently is, pre-compiled Joi schemas continue to work, even with no registered validator (though any options won't be validated):

server.route({
    …,
    options: {
        validate: {
            query: Joi.object({
                …
            })
        }
    }
});

FYI, it's possible that this could be revised to extract the allowed options from the passed Joi object.

[Marsup]

The PR makes sense to me, but applying it on my project causes a whole bunch of errors along the lines of Object literal may only specify known properties, and 'q' does not exist in type 'Validator<never> | DirectValidator<"query">'.. It appears I need to wrap all my object schemas (eg. validate: { query: { q: Joi.whatever() }}) into joi objects, I can't have simple objects anymore. Am I missing something?

[kanongil]

Thank for the feedback. Unfortunately, this will likely take a bit of work to adapt to.

Specifying a validator is required to type such simple validation objects, since it can no longer default to Joi. You would need to use one of the above methods, or explicit casting, to make your Server object accept the Joi validator. You can also override it when specifying the route:

server.route<ReqRefDefaults, typeof Joi>({
    …
})

Of course, you can still just wrap it as suggested, though that would still lose the typings on any validate.options.

[Marsup]

Considering the number of times a user would call server.route, can't we find a better way to define that with some declaration merging?

[kanongil]

But you shouldn't declare it at the route level, but at the server level as in the "registration" section above.

If you are passing the server object to other methods that needs to call server.route() with validations, you will need to explicitly type the expected validator. Eg. function registerRoutes(server: Server<unknown, typeof Joi>) { … }.

I'm not sure what you mean by declaration merging? Do you mean to expect people to merge a DefaultValidator?

declare module '@hapi/hapi' {
    interface DefaultValidator extends Joi.Root {}
} 

This will cause problems for independent plugins, which will either pollute the main project validator, or have to do without.

[Marsup]

I'm torn, you're certainly right, but declaring independent plugins as I do, all the plugins will have to be changed to something like:

const plugin: Plugin<{}> = {
  register(server: Server<{}, typeof Joi>) {
  }
};

It doesn't look like a good DX but I'm not sure there's a better sane choice.

[lenovouser]

I am not sure, but this might also fix #4414. Currently the solution mentioned in that issue works with raw JS, but with TS (which is the reason you would use zod in the first place) it doesn't work and shows type errors everywhere.