Custom JSON Schema type

[flugg]

Greetings!

Superb library - we would love to utilise it in our projects, however, we've created a custom type for our superset of JSON Schema to support our custom vocabularies (including Ajv's $data reference etc.). However, the FromSchema type complaints about the provided type being incompatible with this package's own JSONSchema type.

Any idea how to solve this? Would it be possible to add an option for providing a custom JSON Schema type in some way? Or simply a non-strict version of FromSchema allowing any object?

[ThomasAribart]

Hello @flugg ! FYI, FromSchema already accepts custom types but you would need at least one property in common with JSONSchema:

type MyCustomSchema1 = {
  type: "object";
  custom: 'option';
};

// works fine
type Test1 = FromSchema<MyCustomSchema1>;

type MyCustomSchema2 = {
  custom: 'option';
};

// errors
type Test2 = FromSchema<MyCustomSchema2>;

Maybe I can add & Record<string, unknown> to the constraint, I'll see what I can do.

[ThomasAribart]

(sorry misclick, didn't want to close)

[flugg]

Thanks for the reply @ThomasAribart! I did some checks, and when using FromSchema with a literal schema type (generated from the custom JSON Schema type) everything works. But when trying to create a type that extends FromSchema with type safety for our custom JSON Schema type, it fails. For instance:

type CustomFromSchema<S extends CustomJsonSchema> = FromSchema<S>;

[flugg]

I think I actually found a solution for this:

type CustomFromSchema<S extends CustomJsonSchema> = FromSchema<S extends JsonSchema ? S : never>;

[ThomasAribart]

Yes, indeed you can cast like this :) Can I close this issue ?

[flugg]

Absolutely, this solves my problems. Don't know if this is something you want to add to the documentation or not? Although I guess people interested will find this issue

[ThomasAribart]

Sure I'll add some docs in the FAQ 👍

[ThomasAribart]

@flugg You can now use the ExtendedJSONSchema and FromExtendedSchema types to use JSON Schema extensions:

Cf https://github.com/ThomasAribart/json-schema-to-ts#extensions