Extending string literals in a declaration base in different packages

[azure scroll]

Hi all, I'm trying to create an extendable types, which in turn lets the end user know that if they installed a package, they have access to that string literal, I setup a minimal example, anyone know how I can achieve this with literals?

When trying my example, I always end up with either "AlgoliaProduct" | "AlgoliaCategory" | "AlgoliaCms" or "MagentoProduct" | "MagentoCategory" | "MagentoCms" but never both of them together.

[autumn tundra]

nemuksis#0

Playground Link

Preview:```ts
// @acme/types
export interface SitemapFetcherInterface {
compositions: string & {};
fetchers: string & {};
}

// @acme/package-foo
declare module "@acme/types" {
export interface SitemapFetcherInterface {
compositions: SitemapFetcherInterface["compositions"] | "products" | "category" | "cms";
...```

You can choose specific lines to embed by selecting them before copying the link.

[cloud halo]

Have an interface dedicated for merging, and other packages merge into it like:

interface Composition {
    foo: true
    bar: true
}

Then the actual usage is just composition: keyof Composition.

[azure scroll]

I tried something like this as well, but results in the same thing, see updated example:

[autumn tundra]

nemuksis#0

Playground Link

Preview:```ts
...
type CompositionKeys =
keyof SitemapFetcherInterface["compositions"]
type FetcherKeys =
keyof SitemapFetcherInterface["fetchers"]

// exported function to be consumed by end user
export function sitemapFetcher(
compositionName: CompositionKeys,
fetcherName: FetcherKeys
) {
// unrelated logic here
}
...```

[cloud halo]

That's not quite what I suggested

You'd have to merge top level, declaration merging doesn't allow you to merge inner properties.

So you need something like:

interface Composition {
    foo: true
    bar: true
}

interface Composition {
    baz: true
}

[azure scroll]

Ah I see I did this, it works now

// @acme/types
export interface SitemapCompositionList {}
export interface SitemapFetcherList {}


// @acme/package-a
declare module "@acme/types" {
  export interface SitemapCompositionList {
    products: "products";
    category: "category";
    cms: "cms";
  }
  export interface SitemapFetcherList {
    MagentoProduct: "MagentoProduct";
    MagentoCategory: "MagentoCategory";
    MagentoCms: "MagentoCms";
  }
}

// @acme/package-b
declare module "@acme/types" {
  export interface SitemapCompositionList {
    products: "products";
    category: "category";
    cms: "cms";
  }
  export interface SitemapFetcherList {
    AlgoliaProduct: "AlgoliaProduct";
    AlgoliaCategory: "AlgoliaCategory";
    AlgoliaCms: "AlgoliaCms";
  }
}

[cloud halo]

Yep you can use either the key or the value, and use the other one for metadata if you have any.

[azure scroll]

Thanks!