Declaring TypeScript types for design tokens that use the ES6 module format

[johnny353535]

I'm exporting my design tokens as ES6 modules and I'm having troubles figuring out a way to type these. Currently, I type them with a module.d.ts file as such:

tokens.js

export const ColorWhite = "#ffffff";
export const ColorBlack = "#222222";
...

module.d.ts

declare module 'design-tokens' {
  export const ColorWhite: string;
  export const ColorBlack:string;
  ...
}

As the tokens are generated automatically and a lot of tokens will be added in the future it's kinda tedious. I haven't seen a way to export type declarations atm and also this issue doesn't appear to cover my use case.

Has anyone had the same problem and knows a way around it?

Maybe there is a TypeScript way of declaring the module's exports dynamically? I'm thinking something like this:

declare module 'design-tokens' {
  export const [token]: string;
}

[Pegase745]

I'm handling this through a template like this

1. Create a tempate, with this destination src/templates/typings/es6.template for example

Think of replacing the module name to reflect the real name of your module.

/**
 * Do not edit directly
 * Generated on <%= new Date().toUTCString() %>
 */

declare module 'design-tokens' {
<% _.each(allProperties, function(property) {
%>  export const <%= property.name %>: string;
<% }); %>
}

2. Register your format in build.js

const _ = require('lodash');
const fs = require('fs');
const StyleDictionary = require('style-dictionary').extend('./config.json');

const typingsES6Template = _.template(
  fs.readFileSync(`${__dirname}/src/templates/typings/es6.template`)
);

StyleDictionary.registerFormat({
  name: 'typings/es6',
  formatter: typingsES6Template,
});

StyleDictionary.buildAllPlatforms();

3. Use your new formatter in config.json

You can use any platform name, and destination for this

{
  "source": ["src/**/*.json"],
  "platforms": {
    "js": {
      "transformGroup": "js",
      "buildPath": "dist/",
      "files": [
        {
          "destination": "index.js",
          "format": "javascript/es6"
        }
      ]
    },
    "ts": {
      "transformGroup": "js",
      "buildPath": "dist/",
      "files": [
        {
          "destination": "index.d.ts",
          "format": "typings/es6"
        }
      ]
    },
  }
}

Result

import { ColorWhite } from 'design-tokens';  // <--- No TS errors.

Hope this helps

[monapasan]

As an alternative, you can also generate .ts files. Since typescript can infer simple types this should be enough to import constants without ts errors.

[Pegase745]

It's true, that was my first idea but I was in favor of not adding typescript deps + logic for this.

Also this method will help other developers to type the other js output such as the javascript/module for example

[voslartomas]

Hello, for those who were looking for same solution it seems there is declaration formatter included typescript/es6-declarations.