Scala GitHub Actions

September 4, 2026 · View on GitHub

Scala Continuous Integration (CI) workflow

Runs tests with coverage, binary compatibility, formatting and Scaladoc checks on every pull request and push on "main" branch. Replaces the handwritten ci.yml that each project used to carry.

Setup

Create .github/workflows/ci.yml:

name: CI

on:
  push:
    branches: [ master ]
  pull_request:

permissions:
  contents: read

jobs:
  test:
    uses: evolution-gaming/scala-github-actions/.github/workflows/ci.yml@<sha> # v6.4.0

Nothing else is required if the project uses the defaults below.

Two things about that snippet are deliberate, both because SonarQube Cloud's quality gate rejects the alternatives and drops the security rating to C:

  • the workflow is pinned to a full commit SHA, with the tag in a trailing comment. The snippet writes it as <sha> on purpose, so this README cannot go stale every time v6 moves. Resolve the current value with:

    gh api repos/evolution-gaming/scala-github-actions/git/tags/$(
  gh api repos/evolution-gaming/scala-github-actions/git/ref/tags/v6 --jq .object.sha
) --jq .object.sha

  • there is no secrets: inherit. It is not needed — GITHUB_TOKEN is available to a called workflow automatically, and that is what the Coveralls upload uses. Only the optional Sonar scan needs a secret.

Inputs

inputdefaultnotes
scala_versions'["2.13.18", "3.3.8"]'JSON array; becomes the build matrix
java_version'17'
java_distribution'temurin'
test_taskautotestFull on sbt 2, test on sbt 1, read from project/build.properties
clean_taskautocleanFull on sbt 2, clean on sbt 1, read from project/build.properties
sonarfalserun a SonarQube Cloud scan, see below
sonar_project_key<owner>_<repo>
sonar_args''extra -D arguments for the scanner

Example for a project without sbt-version-policy and on a different Scala set:

jobs:
  test:
    uses: evolution-gaming/scala-github-actions/.github/workflows/ci.yml@<sha> # v6.4.0
    with:
      scala_versions: '["2.13.18", "3.3.7"]'

Jobs in CI pipeline

All checks are run concurrently! Ideally, we must strive to keep them all green, but, it is allowed to merge PR, if some checks are red, for example if code formatting is not introduced, yet. Such red checks must be treated as nudge to improve the quality of code in repo!

  • test-coverage - runs with disabled disk cache for SBT setup action (disk-cache: false) to make sure that test coverage gets run with fully instrumented compilation. The workflow also fails if the produced Cobertura report has no valid lines, so a silently empty report is an error rather than a green build. If project has sonar integration configured and enabled, then sonar scan will get run after coverage reports are uploaded
  • binary-compatibility - runs sbt-version-policy's versionPolicyCheck task on repo with full history (fetch-depth: 0) to make sure that plugin can find the tag for previous version
  • formatting - runs scalafmt's scalafmtCheckRepo task (requires at least version 2.6.2)
  • scaladoc - calls Compile/doc task to make sure that Scaladocs compile

SonarQube Cloud

Most repositories should not use the sonar input. Analysis is done server-side by SonarQube Cloud's Automatic Analysis, which needs no token, no CI step and no repository configuration — that is how kafka-journal and the other analysed repositories work. The sonar input exists for the CI-based scanner, which is the mutually exclusive alternative.

If you do enable it, it scans once, on the first Scala version, importing scoverage's per-module reports. Configuration is passed as scanner arguments, so no per-repo sonar-project.properties is needed.

Three prerequisites, all outside this repo:

  1. A SONAR_TOKEN organization secret. It does not exist yet, so sonar: true will fail until it is added.
  2. The project must already exist on SonarQube Cloud — the scanner reports to a project, it does not create one.
  3. Automatic Analysis must be turned off for that project. It and CI-based scanning are mutually exclusive, and Automatic Analysis wins, so the scan will be rejected while it is on.

The scanner also needs the token passed through, which the caller must do explicitly now that secrets: inherit is gone:

    secrets:
      SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}

Note that the SonarQube Cloud GitHub App creates a check suite on every commit even in repositories it never analyses, which leaves a check permanently queued and reporting no result. Repositories not being analysed should have the app removed rather than left in that state.

Dependency graph workflow

Submits the sbt dependency graph to GitHub. GitHub cannot parse build.sbt natively, so a repo that skips this gets zero Dependabot alerts and looks falsely clean. Every repo adopting these workflows MUST include it.

Setup

Create .github/workflows/dependency-graph.yml, triggered on push to the default branch only:

name: Dependency graph

on:
  push:
    branches: [ master ]

permissions:
  contents: write

jobs:
  submit:
    uses: evolution-gaming/scala-github-actions/.github/workflows/dependency-graph.yml@<sha> # v6.4.0

Resolve <sha> the same way as for the CI workflow above.

The permissions block is required. A called workflow can only downgrade the caller's token, never raise it, so on a repository whose default workflow permissions are read-only the submission fails without it.

A scheduled audit workflow in this repository lists the organization's sbt repos that are missing the caller file and fails while any exist.

Inputs

inputdefaultnotes
java_version'17'
java_distribution'temurin'
modules_ignore''unpublished modules, with binary version, e.g. docs_2.13
configs_ignore'test integration-test scala-tool scala-doc-tool'configurations excluded from the submitted graph

Ignore modules that are never published (documentation, integration tests), so their dependencies do not generate alerts for artifacts nobody consumes:

permissions:
  contents: write

jobs:
  submit:
    uses: evolution-gaming/scala-github-actions/.github/workflows/dependency-graph.yml@<sha> # v6.4.0
    with:
      modules_ignore: 'docs_2.13 docs_3 foo-it-tests_2.13 foo-it-tests_3'

Merge queue (Mergify)

Rebases an approved pull request on the default branch, reruns its CI, then merges it. scala-steward updates are queued without an approval.

Setup

Install the Mergify app on the project and on this repository, then create .mergify.yml:

extends: scala-github-actions

There is no revision to pin, so this file is live for every project extending it as soon as it lands here.

To replace or switch off a single rule, redefine it by name, the local file wins:

extends: scala-github-actions

pull_request_rules:
  - name: queue scala-steward updates
    disabled:
      reason: dependency updates are reviewed by hand here
    conditions: []
    actions:
      queue:

Notes

  • check-success~=^test / is true as soon as one matching check is green, hence the -check-pending~=^test / and -check-failure~=^test / next to it. Bumping Scala versions or renaming a job needs no change here.
  • AI Policy Check is required by the org ruleset, so it belongs in the same list.
  • there is no attribute for "the default branch", hence base~=^(main|master)$. It also keeps stacked pull requests out of the queue.
  • max_parallel_checks: 1 with identical queue and merge conditions gives in-place checks instead of temporary draft pull requests.

Scala Release workflow (v3, v4, v5)

Setup

To use Scala Release workflow have to set up project:

  • add latest sbt-dynver plugin
  • add Evolution's artifactory plugin sbt-artifactory-plugin
  • defined command alias check which runs code quality checks, for example: scalafmt and binary compatibility check by sbt-version-policy: 
    addCommandAlias("fmt", "all scalafmtRepo") // optional: for development
addCommandAlias("check", "all versionPolicyCheck Compile/doc scalafmtCheckRepo")
addCommandAlias("build", "+all compile testFull") // optional: for development
    as very minimum "no-op" placeholder: 
    addCommandAlias("check", "show version")
  • direct publishTo to Evolution's artifactory (for publishing artifacts using sbt-artifactory-plugin): 
    publishTo := Some(Resolver.evolutionReleases)
  • create release.yml file with content: 
    name: Publish Release

on:
  push:
    tags:
      - 'v*'

permissions:
  contents: write # can delete tag on failed release attempt

jobs:
  release:
    uses: evolution-gaming/scala-github-actions/.github/workflows/release.yml@v5
    secrets: inherit

Usage

In project's repo:

  • push tag as separate activity
  • crate new version tag, like git tag v1.2.3 -a -m "release v1.2.3"
  • push the tag, git push origin tag v1.2.3

The above sequence will start Release workflow, which will:

  • run SBT commands +clean; +check; +all test package to verify the build
  • run SBT command +publish to publish packaged artifacts
  • if any of above steps will fail, the workflow will remove git tag - improve code and push fix, later tag again
  • workflow will auto-generate release notes and will publish them
  • go to Code and navigate to Releases
  • review release notes and amend, if required

The v4 version additionally allows overriding SBT commands used by the release job. It is especially useful for projects which have mixed Scala versions in submodules and for which the +, +all SBT features might not work properly:

jobs:
  release:
    uses: evolution-gaming/scala-github-actions/.github/workflows/release.yml@v4
    secrets: inherit
    with:
      # override sbt commands so they don't use "+" because the project uses mixed Scala versions with sbt-projectmatrix
      verify_sbt_command: 'clean; check; all test package'
      publish_sbt_command: 'publish'

Scala Release workflow (v2)

Replaced by v3 because GitHub excluded SBT from ubuntu-latest (details).

Scala Release workflow (v1)

Setup

To use Scala Release workflow have to set up project:

  • add latest sbt-release plugin
  • add Evolution's artifactory plugin sbt-artifactory-plugin
  • defined command alias check which runs code quality checks, for example: scalafmt and scalafix, and binary compatibility check by sbt-version-policy: 
    addCommandAlias("fmt", "all scalafmtAll scalafmtSbt; scalafixEnable; scalafixAll") // optional: for development
addCommandAlias("check", "all versionPolicyCheck Compile/doc scalafmtCheckAll scalafmtSbtCheck; scalafixEnable; scalafixAll --check")
addCommandAlias("build", "all compile test") // optional: for development
    as very minimum "no-op" placeholder: 
    addCommandAlias("check", "show version")
  • direct publishTo to Evolution's artifactory (for sbt-release using sbt-artifactory-plugin): 
    publishTo := Some(Resolver.evolutionReleases)
  • create release.yml file with content: 
      name: Publish Release
  
  on:
    release:
      types: [published]
      branches: [main]
  
  jobs:
    release:
      uses: evolution-gaming/scala-github-actions/.github/workflows/release.yml@v1
      secrets: inherit

Usage

On GitHub:

  • go to Releases page
  • press Draft a new release button
  • make sure that version.sbt file in root of project have correct version string, like 1.2.3
  • in Choose a tag create a new tag (v1.2.3)
  • set Release title to the same string (v1.2.3)
  • press Generate release notes and review them
  • press Publish release button
  • navigate to Actions - there it is possible to follow build's progress

The above sequence will start Release workflow, which will:

  • validate consistency of git tag and version
  • run SBT commands clean; +all check test package to make sure that code quality is good
  • run SBT command +publish to publish packaged artifacts
  • if any of above steps will fail, the workflow will remove git tag and GitHub will mark release notes as draft and it will be possible to adjust code on main branch and attempt publishing again by navigating to drafted release and pressing Publish release button again

When release is published, make sure to amend version.sbt file with next version string.

scalafmt

Minimal configuration requires usage of plugin like:

addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "<latest version>")

scalafix

Minimal configuration requires usage of plugin like:

addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "<latest version>")

binary compatibility

Requires usage of sbt-version-policy plugin like:

addSbtPlugin("ch.epfl.scala" % "sbt-version-policy" % "<latest version>")

scalac options

Evolution's plugin with very strict settings for Scala 2.12 and 2.13 projects

addSbtPlugin("com.evolution" % "sbt-scalac-opts-plugin" % "<latest version>")

Contributing

Contributors from outside the Evolution organization have to sign the Contributor License Agreement before a pull request can be merged. CLA Assistant posts a comment with the link on the pull request, and signing is a one-time click that covers every later contribution.

Revision numbers of known versions

It is suggested to use the very latest version of all workflows. Revision numbers of older versions are provided only for reference purposes!

VersionRevision number
v7.0.161f111a4472fde7b63e5921ac8a238f22d1bb028
v6.4.02a50f1819b6fef2657ba802fd62612b7fc8450f0
v5.1.07803a53309369dbada16835a5414af328fe76d8c