scala-js/scala-js

Scala.js, the Scala to JavaScript compiler

Sébastien Doeraene

@sjrd

Except redesign the internal data structure used for "goto"s in a way that is friendlier to the Scala.js backend.

Daniel Schoepe

@dschoepe

Hi, I'm working on a JVM Scala project, but need to interact with a JavaScript library for parsing JS source map files. My thinking was to define a few shared case classes and then pass data between ScalaJS interacting with the JS library and JVM Scala by converting to and from JSON or some other serialization format. I was wondering if there is already some existing library that automates all the scaffolding around it (e.g. how to invoke the ScalaJS code) or provides another way of calling ScalaJS from the JVM.

Sébastien Doeraene

@sjrd

Have you considered using a JVM library for parsing source maps? There's at least com.google.debugging.sourcemap.SourceMapConsumerFactory in Google's closure-compiler library.

Daniel Schoepe

@dschoepe

As far as I could tell, that's missing some features compared to Mozilla's library. In particular, I couldn't find something similar to computeColumnSpans and wanted to avoid reimplementing that.

Sébastien Doeraene

@sjrd

If you really need the JS library, then you can use any serialization library that cross-compiles for Scala/JVM and Scala.js (most do). What you'll need in addition is how to spawn a process with the JS lib, and how to communicate with it. There, any mechanism to handle IPC would work fine. I can mention https://github.com/scala-js/scala-js-js-envs which is what we use in sbt-scalajs, although it might be overkill for your use case, since it abstracts over several JS engines.

Adam Warski

@adamw

Hey :)

When running JS tests from sbt using scala 3.0.0-RC3 & scalatest, I'm getting an enigmatic [error] Error during tests: and a list of test classes - nothing more. Any hints on how to get more information?

For scala.js 2.13, this works fine

Sébastien Doeraene

@sjrd

Hum, that doesn't seem right. Do you have a reproduction somewhere?

Adam Warski

@adamw

@sjrd https://github.com/softwaremill/quicklens, not a minimized project :)

Sébastien Doeraene

@sjrd

I'll have a look, but probably not today.

Adam Warski

@adamw

ok, thx :) I'll disable the scala3-js for now - it will be in a comment

Daniel Schoepe

@dschoepe

If you really need the JS library, then you can use any serialization library that cross-compiles for Scala/JVM and Scala.js (most do). What you'll need in addition is how to spawn a process with the JS lib, and how to communicate with it. There, any mechanism to handle IPC would work fine. I can mention https://github.com/scala-js/scala-js-js-envs which is what we use in sbt-scalajs, although it might be overkill for your use case, since it abstracts over several JS engines.

Thanks, that looks exactly like what I was looking for actually!

fromscalatohaskell

@fromscalatohaskell_gitlab

JS noob question - how can we refer to require('path/to/image.png') in ScalaJS so that webpack can see my images and not complain? They are seen by my SCSS and transformer to some hash-file thing?

Tobias Schlatter

@gzm0

object A {
  @js.native
  @JSImport('path/to/image.png', JSImport.Namespace)
  val image = js.native
}

2 replies

Chris Kipp

@ckipp:matrix.org

[m]

Can I get some input on some ScalaJS stuff. I recently was given the keys to scoverage so I'm trying to push forward a release, however I'm a bit consued by the sjs1 vs _sjs1.5 versioning scheme for artifacts, and I'm unsure what this should be here: https://github.com/scoverage/scalac-scoverage-plugin/pull/311#discussion_r621883170

it's an odd situation where both the compiler plugin and the runtime is being fully cross released, so the sbt crossproject doesn't include the normal _sjs. So it's being done manually, but am unsure if we actually want the sjs1.5 instead of sjs1

however I'm unsure if that's just a bi-product of the full cross and if that's needed in this scenario

it works int he sbt plugin, but that's because there is some hacky stuff to do a take(3) and add it to the artifact that the sbt plugin is including in the build

Sébastien Doeraene

@sjrd

It should be _sjs1. There's no such thing as _sjs1.5.

2 replies

Naftoli Gugenheim

@nafg

This message was deleted

How can I get source maps to go to some custom uri?

Right now they're going to e.g. http://localhost:8080/custom_fields_shared/src/main/scala/

I want to add a handler in the backend but it should be under some custom path, like /_source_maps/...

Right now they're just 404

In the .js.map they're like /../../../../...

Anton Sviridov

@velvetbaldmime:matrix.org

[m]

@nafg I saw there was a flag for that. Here's an example PR: https://github.com/raquo/Laminar/pull/91/files

Naftoli Gugenheim

@nafg

There's no API in the sbt plugin?

Anton Sviridov

@velvetbaldmime:matrix.org

[m]

🤷‍♂️ right now it seems to be a scalac flag.

Tobias Schlatter

@gzm0

only flag, sorry. We also use that: https://github.com/scala-js/scala-js/blob/d7d9836d934ff5b28dcfd7b5c9c18d10f538e756/project/Build.scala#L1228-L1241

Naftoli Gugenheim

@nafg

All the stuff in scalaJSLinkerConfig is irrelevant?

This message was deleted

Tobias Schlatter

@gzm0

no, that can also be useful (that stuff is very old, and I don't think we have given it an awful lot of thought).

Basically, the compiler options can be useful per compilation unit, the linker config is for everything.

Sorry, I don't have an awful lot of time right now :-/

Naftoli Gugenheim

@nafg

nm, the closest thing is relativizeSourceMapBase which only determines how many dots to put in

ok thanks

vovoks

@vovoks

Hello, guys! Please, tell me how I make Scala Array[Byte] on JS?

Tobias Schlatter

@gzm0

From JavaScript code you mean? You cannot.

(you can create a Scala.js function that creates one, but you cannot do anything with it except for passing it back to Scala.js code).

have a look at js.Array and maybe Int8Array?

vovoks

@vovoks

I mean make JS Array that compatible Scala Array[Byte].

Sébastien Doeraene

@sjrd

JS Arrays and Scala's Array[Byte]s are not directly compatible with each other.

What is your use case?

vovoks

@vovoks

My function on Scala accepting input Array[Byte] I want to call it on JS.

Sébastien Doeraene

@sjrd

As @gzm0 said, either you can write a Scala.js function that would create the Array[Byte] and you export that function to JS; or you can declare your Scala function to accept an input of type js.Array[Byte] or js.typedarray.Int8Array instead.

vovoks

@vovoks

Thank you very much! I'll try it.

Objektwerks

@objektwerks

I haven't worked with Scalajs in a year or so (github.com/objektwerks/scalajs.pool). But I recall the build, package and deploy process was a bit challenging. Has that process improved? Or even evolved into a standard process? TIA!

yurique

@yurique:nowhere.chat

[m]

It might be a bit challenging to define your build if you're starting from scratch :)
After that, it's a matter of running fastLinkJS for development and fullLinkJS for a production build.

There's an option of using the scalajs-bundler which maintains a webpack configuration and runs it under the hood in order to produce bundles ready to be shipped into the browser.

I personally prefer to deal with webpack manually (or experiment with other tools), so I'm usually doing something like this: https://github.com/yurique/frontroute-example or this: https://github.com/tulz-app/laminext/tree/main/website (shameless plug :) ).

Having all this in place, I have one terminal tab with sbt ~fastLinkJS and another one with yarn dev running. And yarn build for production build (after sbt fullLinkJS).

Objektwerks

@objektwerks

@yurique:nowhere.chat Thanks!

August Nagro

@AugustNagro

Wonder if it would be worthwhile to replace js.UndefOr with Scala 3 union + extension methods:

extension [A] (a: A | Unit)

  def isEmpty: Boolean =
    a == ()

  def isDefined: Boolean =
    !a.isEmpty

  def map[B](f: A => B): B | Unit =
    if a.isEmpty then () else f(a.forceGet)

// etc

@main def main(): Unit =
  val a: Int | Unit = 21
  println(a.isDefined)
  println(a.isEmpty)
  println(a.map(_ + 1))

Doesn't seem possible w/ Null union unfortunately.

Sébastien Doeraene

@sjrd

js.UndefOr is a Scala 3 union + extension methods in Scala 3 (well, implicit conversion to value class, but all the same).

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