Support TypeScript declaration merging

Slate: 0.58.1

I’d really like to refine the internal editor types. Typescript supposedly has support for this:

https://www.typescriptlang.org/docs/handbook/declaration-merging.html#module-augmentation

But I think its not working currently, because for example text.d.ts exports a interface Text and a const Text so I think Typescript is having trouble with that.

Ideally, I can just write this code:

declare module "slate" {
	interface Text {
		bold?: string
	}
}

And now the text type everywhere in my codebase has a bold property.

[thesunny]

Declaration merging requires an interface; however, an interface doesn’t support union types.

Because of this, I wonder if we should close this issue in favour of a generic type. An example is a block that can be a paragraph, heading or list. With a type, we can define it as:

type MyElement = Element &
  (
    | { type: "paragraph" }
    | { type: "heading"; level: number }
    | { type: "list-item"; depth: number }
  )

The benefit is that we can use type discrimination:

if (element.type === 'heading') {
  const level = element.level // works!
  // the following would give a useful TypeScript error
  // const depth = element.depth
}

[ccorcos]

Yeah, I don’t like that pattern either (and don’t do it myself). I was just trying to come up with a small and pragmatic solution for you all.

On Wed, May 13, 2020 at 11:59 PM Oleksii Shurubura [e-mail] wrote:

I can confirm that renaming interface Text → interface IText solves this problem.

The prefix I may be confusing and the whole idea of an interface of hiding implementation + not telling anyone that you are using an interface. The practice of having I in front of interfaces leads that you describe parameters, data structures with I which is wrong. It’s a data structure, not interface.

https://stackoverflow.com/questions/31876947/confused-about-the-interface-and-class-coding-guidelines-for-typescript

I, personally, like that slate does not use I prefix.

PS: Microsoft and Facebook do not use it for a reason.

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