Scala tooling ecosystem

Tomasz Godzik @ VirtusLab

Tomasz Godzik

Senior Scala Developer

Who am I

Tomasz Godzik

Senior Scala Developer

also

team lead for Scala Ecosystem Team

Open source tooling

Goals for the talk

Show the full scope of the tooling landscape

Increase confidence in the tooling

Show how you can help!

Mention some useful features.

Tooling landscape

What is a tool?

It's not always clear what is the border between tools and libraries.

For this presentation, a tool is anything that will not be shipped with your code

I am not covering testing frameworks.

And I couldn't cover every tool I wanted :(

Tool

 ❓ Why ❓

Why you might want to use it?

Tool

Tool

⚙️ Features if there is anything worth mentioning

Scala 2 Compiler

 ❓ Why ❓

You need to compile Scala 2 code.

Scala 2 Compiler

Scala 2 Compiler

⚙️ Actionable diagnostics for some of the warnings and errors

⚙️ Improved migration under -Xsource3

⚙️ Smaller features and fixes

Scala 3 Compiler

 ❓ Why ❓

You need to compile Scala 3 code.

Scala 3 Compiler

Scala 3 Compiler

⚙️ Actionable diagnostics for exhaustive checks 

⚙️ Built-in scoverage and semanticdb support

⚙️ Stable presentation compiler

⚙️ New linting

⚙️ Error codes

Metals

• you want direct information from the Scala 2 and 3 compiler
• you want to use new features right from the start
• you want to use different editors

 ❓ Why ❓

Metals

Metals

⚙️ Bazel support released

⚙️ Feature parity between Scala 2 and 3 released

⚙️ Implementations in dependencies coming

⚙️ Inlay hints coming

​⚙️ Work being done on opt in telemetry in progress

Coursier

• You want to manage dependencies both via API or command line
• You want to use a simple package manager for your app
• You want to search dependencies and their versions

 ❓ Why ❓

Coursier

Almond

 ❓ Why ❓

• You want to use Jupyter Lab notebooks with Scala
• You want to use interactive computing such as Spark with Scala

Almond

Scalafmt

• you want uniform formatting across the team and you don't want to waste time on reviews
• you want to use something that is integrated into almost all Scala tooling
• you want to experiment with different styles

 ❓ Why ❓

Scalafmt

Scalafmt

⚙️ optional and fewer braces support

⚙️ numerous bug fixes

⚙️ new settings introduced when necessary

⚙️ up to date with Scala 3 changes

Scala Steward

 ❓ Why ❓

• you want to keep your dependencies up to date and limit tech debt

Scala Steward

Scala Steward

⚙️ Scala CLI support

⚙️ Public instance run by VirtusLab

⚙️ Can be run on github actions

Scalameta

 ❓ Why ❓

• you need to parse or generate Scala code
• you want to get semanticdb information

Scalameta

Scalameta

⚙️ Most work involves keeping up to date with Scala syntax changes

⚙️ Not yet compiled with Scala 3 soon

Wartremover

 ❓ Why ❓

• You want to improve your codebase to avoid common bugs
• You want to add non standard linting 

Wartremover

Wartremover

Caveat: Doesn't currently work in Bloop

Scalafix

• You want to use automatic refactorings to improve your codebase
• You want to implement automatic rewrites.
• You want to automatically improve your compilation speed

 ❓ Why ❓

Scalafix

Scalafix

Caveat: ExplicitResultTypes don't work for Scala 3

Scala CLI

 ❓ Why ❓

• you want to write a simple application or script
• you want to have a simple tool for learning or experimenting

Scala CLI

Scastie

 ❓ Why ❓

• you don't want to use a physical machine
• you want to easily share your experiments
• you want to provide users with examples of your library

Scastie

Scastie

⚙️ Built-in Metals support for hover and completions

⚙️ Tree sitter syntax highlighting

⚙️ Scala CLI support coming soon

Mdoc

 ❓ Why ❓

• you want to type check or run your documentation
• you want to enrich your documentation with some more interactive features
• you want to write custom worksheets

Mdoc

Scala Toolkit

 ❓ Why ❓

 You want to have a ready set of libraries to use as an enhancement of the standard library

Scala Toolkit

Scala Debug Adapter

 ❓ Why ❓

• you want to debug your code in Metals

Scala Debug Adapter

Scala Debug Adapter

⚙️ Hot code reload

⚙️ Faster evaluation of simple expressions

⚙️ Pretty stack traces

More!

• Intellij
• scala native
• scala js
• ammonite
• jardiff
• scalap
• flamegraph
• JMH
• metabrowse
• community build
• tasty query
• tasty inspector

• bloop
• scoverage
• laika
• ZIO Intellij plugin
• scala dependency submission
• sbt version policy
• tasty mima
• mima
• sbt plugins
• scalably typed

​

Tooling

• it's not all bad!
• can and should be improved
• it's possible to contribute and help out

​

How can we do better?

Please report issues!

Sprees?

But, if you want to help or start helping.

We can come try and organize sprees together.

That can be a great way to share knowledge and start to work on the issues that bug you.

But there is more we can do from our side!

Improving reporting

We cannot always easily see what is going wrong.

Adding self diagnostics and reporting mechanisms, which can than be forwarded to us automatically or manually.

Already done in Scastie, soon in Metals opt in.

Improving error messages

It's easier to know what is going on if the error message is clear

Maybe we can fix it automatically?

Improving error messages

But remember

Any feedback is useful! Voice it!