How to use custom validations in encore.ts

[criskell]

How can I use my own validation rules based on the ideas in this PR? #1621

What do you think about this way?

declare const customValidator: (input: string) => boolean;

type X = {
  y: Min<6>;
  z: CustomRule<typeof customValidator>;
};

[marcuskohlberg]

Hey, great catch we had missed publishing the docs for this new feature. Fixed now.
Here you go: https://encore.dev/docs/ts/primitives/validation#value-based-validation-rules

[criskell]

@marcuskohlberg Actually, I was talking about custom validations, where I can pass a custom function at the type level, when the existing validations are not suitable for my use case.

For example, in the deepkit framework this is possible:
https://github.com/deepkit/deepkit-framework/blob/fb1263dbd9fbaae0bd9ecbf40f840698e4523e0c/website/src/pages/documentation/runtime-types/validation.md?plain=1#L316-L329

[marcuskohlberg]

Ah, makes sense. You can create custom validation by composing the built-in rules in the type definition: https://encore.dev/docs/ts/primitives/validation#combining-rules

For custom rules beyond what's possible using the built-in rules, you can do this yourself inside the endpoint handler.

For context, is there a use case where the built-in rules aren't sufficient?