[typebox/value] Property Transformation from One Property to Another

[moontai0724]

Currently, the TypeBox provides useful functions like Cast in Value to transform an object into a target type. However, the transformation is only possible when the property matches the key.

I think to introducing a new feature that allows property transformation from one property to another would be highly beneficial and enhance the capabilities of TypeBox.

import { Type } from '@sinclair/typebox';
import { Value } from '@sinclair/typebox/value';

const User = Type.Object(
  {
    id: Type.String({
      key: 'userId',
    }),
  },
);

const transformResult = Value.Cast(User, {
  userId: '100',
});

console.log(transformResult); // Expect: `{ id: '100' }`

[sinclairzx81]

@moontai0724 Hi,

There is a partially implemented version of transforms available in the examples/transform directory.

https://github.com/sinclairzx81/typebox/tree/master/examples/transform

import { Transform, Encode, Decode } from './transform'

const User = Transform(Type.Object({
  id: Type.String()
}), {
  decode: (value) => {
    return { userId: value.id }
  },
  encode: (value) => {
    return { id: value.userId }
  }
})

const decoded = Decode(User, { id: '100' })  // const decoded = { userId: '100' }

const encoded = Encode(User, decoded)        // const encoded = { id: '100' }

This implementation is pending inclusion in the library until it's had a good review and all the requirements ironed out, however you can use this module today by copying and pasting the transform.ts into your project. All feedback is welcome on the module.

[moontai0724]

Excellent! looking forward to release!

[sinclairzx81]

@moontai0724 Hi,

There feature should be landing very soon. There is currently tagged dev revision published to NPM that you can install and try today.

npm install @sinclair/typebox@dev

Revision notes for the release can be found on the PR here #525
Cheers
S