Meta Joins Kotlin Foundation
engineering.fb.com
engineering.fb.com
You can just run JavaScript right out of the url field or the console in the browser, no compilation or server required - that’s what I would think of as ‘native.’
I am also wondering if Meta still uses PHP or Hack.
Meta’s WWW codebase is its oldest, and still written in Hacklang. Lots of internal tooling is also written in Hack.
I wouldn’t be surprised if there are more committed lines of Hacklang than any other language (although, a good chunk of that is codegen, vs other core languages where codegen is part of the build process).
Even otherwise, at the scale the company operates it's much better to run codegen once at commit time rather than recreate the entire codebase on every deploy (several times a day) which would take forever.
If Java ever ships Valhalla we might get null restricted types: https://openjdk.org/jeps/8316779
Java is the only language that I'm aware of with checked exceptions (Swift has "throws" which I guess goes in that direction but is untyped) and it's in my experience not notably exception-safer than languages that use values for error handling (such as Rust, Haskell or Kotlin).
Swallowing exceptions because of bad ergonomics or misuse by library authors is unfortunately fairly common in a lot of Java code that I've seen. By contrast, most Kotlin code that I've seen uses exceptions only for unrecoverable errors and otherwise uses some sort of sum type (Result, Either or some sealed class/interface). These can be handled ergonomically and in a very type-safe manner - and importantly they don't break when used with higher-order functions. In the future, Kotlin will have Rich Errors which will have even better ergonomics (I'm personally fine with Either, but I know some people dislike a heavily functional style, so this will be good for them).
> Swallowing exceptions because of bad ergonomics or misuse by library authors is unfortunately fairly common in a lot of Java code that I've seen
This is because the language has not invested to make the ergonomics better. Checked exceptions/errors are still superior than runtime exceptions. "Misuse" can still occur with values. Bad developers can still bubble errors they can't handle and that you can't handle either. I've written elsewhere [0] the things that Java needs.
> By contrast, most Kotlin code that I've seen uses exceptions only for unrecoverable errors
Except for the whole Kotlin standard library. Like you said the errors as unions proposal is very far away. So either I need to adopt some library and then when unions come I now have 2-3 competing systems + whatever the libraries are using. I'd rather just use checked exceptions.
> - and importantly they don't break when used with higher-order functions.
This is not a property of values or exceptions. It's a property of the type system. Checked exceptions can work perfectly fine with higher order functions, Scala has done good research there [1] and I believe Swift's typed throws works with lambdas as well; Java just hasn't invested in the language.
Ultimately, there is no difference because Result<T, Error> and T func() throws Exception. One is not superior to the other. What it comes down to for me is whether a language has support for checked errors or not, and Kotlin does not.
[0] https://news.ycombinator.com/item?id=44432640
[1] https://docs.scala-lang.org/scala3/reference/experimental/ca...
That's why Kotlin's philosophy is and has for a long time been "use values for expected and recoverable errors, runtime exceptions for unexpected and unrecoverable conditions", see: https://elizarov.medium.com/kotlin-and-exceptions-8062f589d0...
> Except for the whole Kotlin standard library.
I'm not sure what you mean. Most kotlin stdlib functions that can fail have some sort of "...orNull" variant to be used when you're not sure you're going to get something back, and there's "runCatching" which will wrap any exceptions in a Result type.
Result is part of the stdlib, so you don't have to use any library, although some people (me included) prefer Either. If/when they introduce Rich Errors, it's going to be semantically almost equivalent to Either, except you get somewhat improved ergonomics, so it's not really a paradigm shift.
> Ultimately, there is no difference because Result<T, Error> and T func() throws Exception. One is not superior to the other. What it comes down to for me is whether a language has support for checked errors or not, and Kotlin does not.
I don't understand how those two sentences don't contradict each other. Kotlin has support for Result<T> (stdlib) or Either<E, T> (from libraries like Arrow). Since you're agreeing that this is equivalent to checked exceptions I don't understand how you can claim that Kotlin doesn't support checked errors. It supports them just as well as Java does, it just has a different philosophy around it. (I guess the one point that I'll concede is that it can cause issues when interfacing with Java code and it would be nice if Kotlin had some better ergonomics around automatically inferring errors from Java library code the way it does for nullability checks; but in practice this hasn't been a big issue for me).
FWIW, I disagree that there isn't a big distinction. If the exception is part of the regular type, it is a value and it can be manipulated like any other value, making it very easy to write all sorts of code that manipulates exceptions. Of course, you could eventually write enough machinery so that you get the same power also with checked exceptions, but that just makes the language more complicated for questionable gain. And in any case, Java doesn't do that.
The Scala discussion you're linking is certainly interesting, but it's cutting-edge PL research (effect systems). I'm not sure how this matters in a discussion of tradeoffs between Java and Kotlin today.
\kotlin\libraries\stdlib> gci -r | where extension -eq .kt | where name -ne Result.kt | grep "\): Result<" | measure-object | select count
Count
-----
0
\kotlin\libraries\stdlib> gci -r | where extension -eq .kt | grep "throw " | measure-object | select count
Count
-----
1176
Additionally, the above-linked JEP only proposes to make a small subset of types potentially null-safe. The goal there is performance, not correctness.
> Enhance Java's reference types to let programmers express whether null references are expected as values of the type
That seems really very limiting and like it would make the feature not very useful in practice.
It will eventually be a goal. Java does things in steps. First will be introducing the syntax, then another JEP will take care of the standard library. Just like they introduced virtual threads and then introduced structured concurrency. Or like introducing records and then introducing pattern matching over records. Baby steps.
Kotlin provides a lot of 'clever' syntactic sugar and features that makes certain things that are quite verbose in Java, nice and compact in Kotlin. It also means that there are many way to achieve the same thing in Kotlin. Once you've learned everything it allows you to do things that would take a lot of Java in much fewer lines of code. But there is also just more 'stuff' to learn in the Kotlin language.
Java is a much simpler language than Kotlin with relatively few features, but this simplicity means you sometimes have to build quite verbose structures to achieve what you want.
So which is 'simpler' very much comes down to how you define 'simple'.
I also think that checked exceptions are a major flaw (particularly because they don't work well with lambdas) but I don't foresee them getting removed anytime soon.
Kotlin's one big advantage is having avoided the "billion dollar mistake" of null pointers. Or at least, mitigated it. But in my opinion it's not sufficient to install a whole new language into your stack.
I believe I read on the mailing list it’s implemented here: https://github.com/openjdk/valhalla/tree/lw5
Kotlin is incredibly expressive and can get quite complicated. Java is a bit more brutally simple (and obviously more verbose).
As a C# dev primarily, I love Kotlin, and I've always hated Java despite it being the very first language I learned.
I wouldn't call Kotlin simple by any stretch of the imagination. It's just a very high-level language.