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RBS, Ruby’s new type signature language

developer.squareup.com

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Re: RBS, Ruby’s new type signature language

#11

Post by avolcano »

monadic2 wrote: post #6

How does this interact with method_missing, the soul of rails? Obviously much of the rails api is defined dynamically, not statically. I could see runtime checks having some value but I’m not sure how an IDE could take advantage of this, period. I’d imagine you’d at least need to generate methods (rather than parse and route messages at runtime) to make this remotely viable. I’m not super familiar with ruby outside o…

You're correct in your assumption you'd need to generate methods, from my quick investigation into how Sorbet handles it - see https://github.com/chanzuckerberg/sorbet-rails for some details.

Re: RBS, Ruby’s new type signature language

#12

Post by ucarion »

avolcano wrote: post #9

Didn't realize Square was interested in Ruby type checking, just like their competitors over at Stripe. Lots of money riding on Ruby, I guess :) It does seem useful to have a _standard_ for type definitions - RBS as the equivalent to a .d.ts file - as that allows for different type checking implementations to use the same system under the hood. This was a big problem for Flow, and why it lost the fight as soon as Typ…

For other readers: "Sorbet" refers to https://sorbet.org/, Stripe's Ruby type checker.

Re: RBS, Ruby’s new type signature language

#13

Post by recursivedoubts »

bytematic wrote: post #8
recursivedoubts wrote: post #3

Cool. And glad to see this called out: Better IDE integration: Parsing RBS files gives IDEs better understanding of the Ruby code. Method name completions run faster. On-the-fly error reporting detects more problems. Refactoring can be more reliable! IDE support (autocomplete, refactoring and quick documentation) is the most important reason to annotate argument and return types.

I've been using typescript for a few years now and to be honest I almost never rely on the compilation errors. I just use the built in Jetbrains IDE completion, autosuggestion, and navigation to make it work.

Yep. A good IDE to a first approximation doesn't allow compilation errors to occur because you are auto-completing everything, including symbol completion based on the type at cursor, etc.

Jetbrains is a wonderful company.

Re: RBS, Ruby’s new type signature language

#14

Post by hartator »

> Typed languages are suitable for larger projects but are often less flexible. Untyped languages allow for rapid development, but scaling teams and codebases with them can be difficult.

Well some of us disagree with the statement that untyped is not suitable for large teams. And that's why we use Ruby. There is a lot of very good typed languages out there if you do want typed. I feel Square and Stripe are pushing their own codebase issues onto general Ruby - as it's our problem to solve - which is not cool.

Re: RBS, Ruby’s new type signature language

#15

Post by azinman2 »

CarelessExpert wrote: post #10
azinman2 wrote: post #2

Interesting. I’m surprised they didn’t opt to do this inline with the rest of the ruby code, because now they can diverge from each other. It’s a bit like a separate header file in C/C++/Obj-C, except in those cases the compiler will yell at you if the implementation doesn’t match the header. Having it blow up at runtime instead doesn’t feel like such a big change from the way it is now, other than helping out IDEs.

> I’m surprised they didn’t opt to do this inline with the rest of the ruby code, As they mention in the post, they followed typescript's approach, here. The benefit is it allows you to layer in typing into an existing codebase in a non-disruptive way.

But as I mentioned the downside of this is that any mistakes don't become evident until at runtime. While the python way has the same problem (they're not compiled languages after all), by inlining to the existing source there's less changes for divergence to happen.

Re: RBS, Ruby’s new type signature language

#16

Post by muglug »

Can someone explain why the types cannot live in Ruby code itself (after an appropriate version bump)?

Python 3 incorporated types into the language itself, in a similar way (though non-reified) to PHP. This seems much easier to deal with than requiring two files (.rb and .rbs) to describe a single data structure.

Re: RBS, Ruby’s new type signature language

#18

Post by ch_123 »

> Typed versus untyped is a 30-year-old issue for programming languages.

I'm pretty sure the merits of typed vs untyped has been going on since the 1950s at least. 30 years is such a specific period of time that it makes me wonder what happened in the early 90s that the author is referring to.

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