[rewma]

> The problem is that I have perfectly valid collections of data (...) and static typing systems make this very powerful and legitimate task a nightmare.

What leads you to believe that static typing turns a task that essencially boils down to input validation "a nightmare"?

From my perspective, with static typing that task is a treat and all headaches that come with dynamic typing simply vanish.

Take for example Typescript. Between type assertion functions, type guards, optional types and union types, inferring types from any object is a trivial task with clean code enforced by the compiler itself.

[brundolf]

Presumably the GP's data is external and therefore not checkable or inferrable by typescript. This makes the task less ideal, but still perfectly doable via validation code or highly agnostic typing

[rewma]

> Presumably the GP's data is external and therefore not checkable or inferrable by typescript.

There is no such thing as external data that is not checkable or inferable by typescript. That's what type assertion functions and type guards are for.

With typescript, you can take in an instance of type any, pass it to a type assertion function or a type guard, and depending on the outcome either narrow it to a specific type or throw an error.

[brundolf]

You said:

> inferring types from any object is a trivial task

This is true for values defined in code, but TypeScript cannot directly see data that comes in from eg. an API, and so can't infer types from it. You can give the data types yourself, and you can even give it types based on validation logic that happens at runtime, and I think this is usually worth doing and not a huge burden if you use a library. But it's disingenuous to suggest that it's free.

The closest thing to "free" would be blindly asserting the data's type, which is very dangerous and IMO usually worse than not having static types at all, because it gives you a false sense of security:

  const someApiData: any = { foo: 'bar' }

  function doSomethingWith(x: ApiData) {
    return x.bar + 12
  }

  type ApiData = {
    foo: string,
    bar: number
  }

  // no typescript errors!
  doSomethingWith(someApiData as ApiData)

The better approach is to use something like io-ts to safely "parse" the data into a type at runtime. But, again, this is not without overhead.

[rewma]

> This is true for values defined in code, but TypeScript cannot directly see data that comes in from eg. an API, and so can't infer types from it.

No, that's not right at all. TypeScript allows you to determine the exact type of an object in any code path through type assertions and type guards.

With TypeScript you can get an any instance from wherever, apply your checks, and from thereon either throw an error or narrow your any object into whatever type you're interested in.

I really do not know what leads you to believe that TypeScrip cannot handle static typing or input validation.