Syntatic sugar for callable namespaces (functions as namespace)

[KSXGitHub]

I have a suggestion: I love to write callable namespaces but I don't want to write its name twice (one for function, one for namespace), so I propose a syntax sugar for this:

export namespace myFunc {
  (x: number) => square(2 * x)
  export const square = (x: number) => x * x
}

This should be equivalent to:

export function myFunc (x: number) {
  return myFunc.square(2 * x)
}

export namespace myFunc {
  export const square = (x: number) => x * x
} 

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Search Terms:
callable namespace syntax sugar

[AlCalzone]

Related, but not sure if duplicate:
#21572
#15868

[KSXGitHub]

@AlCalzone I'm sure that they are not even related. The first is interface declaration which is a type rather than an object at runtime while functions are objects being created during runtime. As for the second one, I don't see how it's related to this at all.

[mhegazy]

I would consider this a dupe of #15868.

#15868 is JS syntax, and no need to create new constructs if one already exists.

[KSXGitHub]

@mhegazy Okay, I can see how #15058 would "solve" my problem but it has its own limitation:

1. Namespace can contain type declarations, assignment cannot.

2. Within a namespace, members can refer to each other without specifying namespace's name (e.g. when myFunc calls myFunc.square in the first code snippet: it called square(), not myFunc.square).

3. Add quick fix for exporting "private" entities when imported indirectly for --declaration #15058 actually makes it more verbose/complicated than both two code snippets above: When I need to declare multiple namespace members, I need to write myFoo only once in the first snippet or twice in the second snippet but multiple times in Add quick fix for exporting "private" entities when imported indirectly for --declaration #15058, so it didn't solve my problem at all.

4. Add quick fix for exporting "private" entities when imported indirectly for --declaration #15058 is harder for TypeScript compiler to check: What if I assign properties in a loop or from a different file?

[mhegazy]

We already have a syntax for function + namespace; that already cover all your needs up there.

The request here is to add a new syntax for shorter declaration of function+namespace combo. So it covering all the features of the existing syntactic form is not the goal.

Here is my rational, First, we should not have two ways of declaring the same construct, unless there is a very good reason. Second, the proposal in the OP does not get us closer to a natural JS model. And it is one of our goals to be as close to JS as possible; we have already said we want to do the proposal in #15058, as it is identical to what you write in JS. that all said, if we were to add a new shorter form, it would be the one in #15058.

And as for 1, 2 and 3, you should use function + namespace declarations to achieve that. that also applies if you want to have multiple overloads for your function, or you want to declare the properties as const.

As for 4, no, that would not be allowed. only top-level assignments would be allowed with #15058.

[typescript-bot]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.

[bluelovers]

@mhegazy where is that syntax for function + namespace ?

can u post a link?

[AlCalzone]

https://www.typescriptlang.org/docs/handbook/declaration-merging.html scroll down to about 2/3.

function buildLabel(name: string): string {
    return buildLabel.prefix + name + buildLabel.suffix;
}

namespace buildLabel {
    export let suffix = "";
    export let prefix = "Hello, ";
}