The document outlines various tools and techniques to enhance productivity in Scala development, including scalafmt for code formatting and scalafix for linting and refactoring. It also discusses using GitHub Actions for continuous integration and deployment pipelines, along with features like sbt templates and Scala Steward for automated maintenance. Additionally, it highlights the importance of collaboration tools and provides guidance on setting up configurations for effective Scala programming.

1. 1
Boost your productivity
with Scala tooling!
Meriam Lachkar
@meriamLachkar

2. Meriam Lachkar
@meriamLachkar
Software engineer @Scala center
Worked on:
- Scalafix
- Scala3-migrate
- Metals
- Scaladex

3. Open source
Education
- Metals
- Scalafix
- Scaladex
- Scala 3 migration guide
- Scala debugger
- Scala.js
- Scala native
- ...
- Functional Programming Principles in Scala
- Functional Program in Scala
- Parallel Programming
- Programming Reactive Systems
- Big data analysis with Scala and Spark
- Functional Programming in Scala Capstone
- Effective Programming in Scala
Scala
2/3
Scala
2
Scala
3

4. I - Tools to rewrite and lint the code
II - Tools to collaborate within the team
III - Tools to maintain code
IV - Tools to explore the ecosystem
Table of contents

5. Scalafmt
Rewrite and linting

6. Scalafmt
6

7. Scalafmt: Installation
Download the script using coursier
7
> coursier bootstrap scalafmt -o scalamfmt
> bin/scalafmt
Reformatting...
100.0% [##########] 170 source files formatted
> bin/scalafmt --test
All files are formatted with scalafmt :)
Run and test Scalafmt

8. Scalafmt: homogeneous user experience
- Continuous Integration
8
- Locally through scalafmt command
- Intellij/Metals

9. Scalafmt: Configuration
9
//.scalafmt.conf
version = "3.0.6"
maxColumn = 120
project.git = true

10. 10
//.scalafmt.conf
align.preset = none/some/more/most
fileOverride {
"glob:**/*.sbt" {
align.preset = most
}
}
Scalafmt: Configuration (2)

11. Scalafmt: Configuration - rules
11
//.scalafmt.conf
rewrite.rules = [RedundantBraces, AvoidInfix]

12. Scalafmt: Configuration - rules
12
//.scalafmt.conf
rewrite.scala3.removeOptionalBraces = yes
rewrite.scala3.convertToNewSyntax = true

13. Scalafmt: Configuration
13
//.scalafmt.conf
version = "3.0.6"
maxColumn = 120
project.git = true
align.preset = none/some/more/most
fileOverride {
"glob:**/*.sbt" {
align.preset = most
}
}
rewrite.rules = [RedundantBraces, AvoidInfix]
// in scala 3
rewrite.scala3.convertToNewSyntax = true
rewrite.scala3.removeOptionalBraces = yes

14. Scalafix
Rewrite and linting

15. Linting
Refactoring
What does it do ?
15

16. Scalafix: Installation
16
// project/plugins.sbt
addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.9.31")
//build.sbt
semanticdbEnabled := true, // enable SemanticDB
Install Scalafix
Run Scalafix
sbt:main> ScalafixAll
[info] Running scalafix on 1 Scala sources
[success] Total time: 0 s, completed 22 Oct 2021, 15:39:50
sbt:main> ScalafixAll --check
[info] Running scalafix on 1 Scala sources
[success] Total time: 0 s, completed 22 Oct 2021, 15:39:50

17. Scalafix: rules
17
- DisableSyntax
- noVars
- noThrows
- noNulls
- ...
- ProcedureSyntax
- ExplicitResultTypes
- RemoveUnused
- Imports
- Private members
- Pattern vars
- ...
Syntactic rules
Semantic rules

18. Scalafix - Custom rules
18

19. Scalafix - Custom rules
https://www.youtube.com/watch?v=-l7pV0sFq1c
19

20. Scalafix-organize-imports developed by Cheng Lian
20

21. Github actions
Collaborations tools

22. Github actions
- Automate many workflows including CI and CD
- Manage your workflows with the same tool you already use everyday
- Simple setup of pipelines
22
Event
Jobs
Jobs
Jobs

23. Github actions: CI
23
jdk11:
name: test on jdk11
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v2
- uses: olafurpg/setup-scala@v10
with:
java-version: adopt@1.11
- run: sbt test
on:
push:
branches:
- main
Pull_request:
checks:
name: Scalafmt and Scalafix
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v2
- uses: olafurpg/setup-scala@v10
- run: sbt "scalafix --check"
- run: ./scalafmt --test
Event
Jobs

24. Publish a regular release when a git tag is created
Github actions: sbt-ci-release
24
Publish a snapshot version for each push on `main`
1
2

25. Github actions: Releases
25
name: Release
on:
push:
branches: [main]
tags: ["*"]
Event
jobs:
publish:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v2
- uses: olafurpg/setup-scala@v13
- name: Publish ${{ github.ref }}
run: sbt ci-release
env:
PGP_PASSPHRASE: ${{secrets.PGP_PASSPHRASE}}
PGP_SECRET: ${{secrets.PGP_SECRET}}
SONATYPE_PASSWORD: ${{secrets.SONATYPE_PASSWORD}}
SONATYPE_USERNAME: ${{secrets.SONATYPE_USERNAME}}
Job
> git tag -af "v$VERSION" $COMMIT_HASH -m "v$VERSION" &&
git push -f origin v$VERSION

26. Github actions: Release notes
26
on:
push:
branches:
- main
update_release_draft:
runs-on: ubuntu-latest
steps:
- uses: release-drafter/release-drafter@v5
env:
GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
template: |
## Pull Requests
$CHANGES
Event
Job

27. Github actions: Release notes 2
27
categories:
- title: '🚀 Features'
labels:
- 'feature'
- title: '🐛 Bug Fixes'
labels:
- 'bug'
- title: ' Maintenance'
label: 'chore'
default: patch
template: |
## What’s Changed
$CHANGES

28. sbt templates
Collaboration tools

29. sbt templates
29
> sbt new scala/scala3.g8
A template to demonstrate a minimal Scala 3 application
name [Scala 3 Project Template]: MyScalaProject
Template applied in /Users/meriamlachkar/scalacenter/myscalaproject
> coursier install giter8
> g8 scala/scala3.g8
Alternative way to use templates

30. sbt templates
30
> g8 scalacenter/scalafix.g8
repo [scalafix-my-rules]: scalafix-scala3-rules
scalafix_version [0.9.31]:
Template applied in /Users/meriamlachkar/scalacenter/.
> rules/main/scala/fix/YourRule.scala// simple rule
> input/ // the
input file before scalafix has run
> output/ // expected
file after scalafix has run
> tests // test
suite to launch
Project’s structure

31. Sbt templates - create your own template
31
> sbt new myCompanyTemplate.g8
> .github/workflows // common workflows for CI and Release
> .scalafmt.conf // scalafmt configuration
> .scalafix.conf // scalafix configuration
Project’s structure

32. Scala steward
Maintenance tools

33. Scala steward
33
https://github.com/scala-steward-org/scala-steward/blob/master/docs/running.md

34. // .scala-steward.conf
pullRequests.frequency = "0 0 1,15 * ?"
Scala steward
34

35. Scala steward with scalafix rules
35
override def fix(implicit doc: SemanticDocument): Patch =
Patch.replaceSymbols(
"org.scalatest.FunSuiteLike" -> "org.scalatest.funsuite.AnyFunSuiteLike",
"org.scalatest.FunSuite" -> "org.scalatest.funsuite.AnyFunSuite",
...
)
> scalafix --rules= https://githubusercontent.com/ruleFile.scala

36. mdoc
Maintenance tools

37. extensible
no dead links
Mdoc
37

38. Mdoc
38
// project/plugins.sbt
addSbtPlugin("org.scalameta" % "sbt-mdoc" % "2.2.24" )
// build.sbt
lazy val myproject = project // your existing library
.settings(...)
lazy val docs = project // new documentation project
.in(file("myproject-docs"))
.settings(
mdocVariables := Map("VERSION" -> version.value)
)
.dependsOn(myproject)
.enablePlugins(MdocPlugin)
> docs/mdoc
Run mdoc

39. Mdoc: custom modifiers
39
```scala mdoc:scalafmt
assumeStandardLibraryStripMargin = true
align.stripMargin = true
---
val example1 =
s"""Examples:
| * one
| * two
| * $three
|""".stripMargin
```
Generated documentation

40. ```scala mdoc:file:incompat-30/type-of-implicit-def/README.md
```
Mdoc: custom modifiers
40
class FileModifier extends StringModifier {
override def process(info: String,
code: Input,
reporter: Reporter): String = {
val file = AbsolutePath(info)
if (file.isFile) {
FileIO.slurp(file, StandardCharsets.UTF_8).trim
} else {
val pos = Position.Range(code, 0 - info.length - 1, 0 - 1)
reporter.error(pos, s"no such file: $file")
""
}
}

41. Mdoc: docusaurus
41

42. mdoc: deploy-website
42
on:
push:
branches: [main]
tags: ["*"]
Event jobs:
publish:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v1
- uses: olafurpg/setup-scala@v13
- name: Publish ${{ github.ref }}
run: sbt docs/docusaurusPublishGhpages
env:
GITHUB_DEPLOY_KEY: ${{ secrets.DOC }}
Job

43. Scaladex
Explore the ecosystem

44. Scaladex
44

45. Scaladex: version matrix
45

46. Other tools

47. Other tools
- Sbt server (youtube video)
- Coursier install
- Sbt-explicit-dependencies
- Scastie
- sbt-scoverage
47

48. Special thanks to all maintainers
48

49. Thank you!