What is the preferred IDE for Scala (other than IntelliJ IDEA)?

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12

  1. In emacs >= 29.1, they natively provide eglot, a client for language server protocol (lsp). If you have lower version of emacs, you need to install eglot. So it will use metals as Scala LSP.

  2. Install metals for emacs as followed.

coursier bootstrap \
  --java-opt -XX:+UseG1GC \
  --java-opt -XX:+UseStringDeduplication  \
  --java-opt -Xss4m \
  --java-opt -Xms100m \
  --java-opt -Dmetals.client=emacs \
  org.scalameta:metals_2.13:1.3.5 -o metals -f

I learn this from the metals’ website here. It says that

The -Dmetals.client=emacs flag is important since it configures Metals for usage with Emacs.

But they did not add it into their formula, to my surprise. So I add it here.

  1. Once you have installed metals, put it anywhere that PATH could find it.

  2. Here is my Scala configuration. I also have some key bindings for eglot, which include the common commands I use often. When you open your Scala file, it should be under Scala-mode. And you can then M-x eglot to start metals automatically.

  3. If you want to use Ammonite as REPL, I have a script:

import os._
import ammonite.* 

object AmmMain {
  def main(args: Array[String]): Unit = {
     ammonite.Main().run()
  }
}

Then you can use SBT to run the main function AmmMain to enter Ammonite REPL.
Note that the latest Ammonite supports Scala 3.5.1, here is how I add it in my build.sbt

libbraryDependencies += "com.lihaoyi" % "ammonite" % "3.0.0" cross CrossVersion.full

Hope you can use metals successfully in your Emacs. Previously, before metals, I used ENSIME a lot. and it just worked and was really great! I am a big fan of ENSIME. But once it was archived, I tried to use it but failed lots of times. So now I use metals, which is also an amazing tool.

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