[TypeScript] Action Type

[NickClark]

Describe the bug

An action type should be available to developers. One is available if you stay within a *.svelte file, but isn't present outside of it.

Reproduction

Define an action in your svelte file:

function onResize(
  node: HTMLDivElement,
  callback: (entry: DOMRectReadOnly) => void,
): SvelteActionReturnType {
  // ...
}

and the types work.

Move the action outside to its own module, and you no longer have any types you can import to ensure action type.

Maybe something like this would work:

type SvelteActionReturnType<P> = {
  update?: (newParams: P) => void;
  destroy?: () => void;
} | void;

type SvelteActionType<P> = (
  node: Element,
  params: P,
) => SvelteActionReturnType<P>

Logs

No response

System Info

System:
    OS: Linux 5.4 Ubuntu 20.04.2 LTS (Focal Fossa)
    CPU: (24) x64 AMD Ryzen 9 5900X 12-Core Processor
    Memory: 14.89 GB / 24.99 GB
    Container: Yes
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 16.2.0 - ~/.asdf/installs/nodejs/16.2.0/bin/node
    npm: 7.13.0 - ~/.asdf/installs/nodejs/16.2.0/bin/npm
  npmPackages:
    svelte: ^3.38.2 => 3.38.2
    vite: ^2.3.7 => 2.3.7

Severity

annoyance

[tanhauhau]

@dummdidumm do we already have svelte action type definition defined in language tools?

[benbender]

@tanhauhau @dummdidumm Doesn't seem so and would be a very nice addition! I was searching for one just yet and couldn't find it...

PS: Many thanks for your tremendous work on the tooling. Very much appreciated!

[jasonlyu123]

There's only the action return type in language tools, because svelte2tsx now just transforms use:action to an action function call. There's one before and it's similar to the one OP proposed. Just the element is also a generic parameter.

[dummdidumm]

Such a type makes sense to add. Note to self: We should filter out the global svelte2tsx completions to avoid such confusion in the future.
Question is what's the best name and where to put this. @Conduitry what do you think about a new import path, like svelte/action or svelte/actions ? Names for the types could be Action and ... I don't know a good name for the return type 😄

[ghostdevv]

Is there any progress on typing for an action?

[Conduitry]

This should be fixed in 3.46.5. (Probably should have been 3.47.0, whoops.)