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RBS, Ruby’s new type signature language

(developer.squareup.com)
511 points mootrichard | 8 comments | 29 Jul 20 18:04 UTC | HN request time: 0.465s | source | bottom
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freedomben ◴[29 Jul 20 19:31 UTC] No.23990680[source]▶
I'm not thrilled about the separate files with the type information but I completely understand why they did it, and if it were my choice I might make the same one.

I don't like the comparison with TypeScript `.d.ts` files however, because TS still lets you do types inline in the code. I haven't seen it mentioned anywhere that this won't be supported by Ruby 3.

Does anybody know if Ruby 3 will also support inline type information or will the header RBS files be required?

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1. amw-zero ◴[29 Jul 20 19:59 UTC] No.23990915[source]▶
I much prefer separate files for type declarations. Or at least the ability to define them separately. Type annotation takes away from readability. I like keeping the types and code separate.
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2. hombre_fatal ◴[29 Jul 20 20:07 UTC] No.23990990[source]▶
The upside of external files is pure incremental implementation that touches no other tooling and requires no buy-in.

I don't see how having to switch files to know that `input` is a `User` increases readability, though. It seems like straight-forward impl-simplicity trade-off, not one of user ergonomics.

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3. untog ◴[29 Jul 20 20:17 UTC] No.23991109[source]▶
> Type annotation takes away from readability.

I don't disagree, but I think it's a very minor issue given that it's trivial to use color to highlight code these days. By comparison having to switch between two files (and keep them in sync!) when making changes is a far bigger usability concern.

4. strogonoff ◴[29 Jul 20 20:29 UTC] No.23991228[source]▶
Separating type definitions from code can be considered as contributing to readability of idiomatic Ruby on one hand, and type definitions on the other, taken separately on their own—by not imposing constraints on either syntax.

IDEs will likely be able to seamlessly peek/go to RBS type definition on any Ruby identifier in any case.

5. benrbray ◴[29 Jul 20 20:30 UTC] No.23991234[source]▶
> Type annotation takes away from readability.

Do you mean for Ruby specifically or in general? I've found that it's much easier to (safely, accurately) read, use, and extend e.g. a TypeScript file than its JavaScript counterpart, even when provided with a .d.ts file.

6. mekster ◴[29 Jul 20 20:32 UTC] No.23991261[source]▶
That can be covered by the editor to give the user some hint by referencing the external file but for the user, having have to keep adding it on a separate file seems pretty annoying as you need to keep declarations synched in 2 files.

Also how do you type something in an inline function?

7. wolfadex ◴[29 Jul 20 21:10 UTC] No.23991625[source]▶
Type annotations aren't inline in all languages. If you're writing Haskell or Elm, as a few examples, then you get static types without having to write them out and if you do write them out they sit above the function that uses them.
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8. ric2b ◴[29 Jul 20 22:29 UTC] No.23992289[source]▶
I don't think anyone is disappointed that it isn't literally inline, the problem is that it's in separate files.