Release Scala 2.12.16

[SethTisue]

Variables to be expanded in this template (or set and export them in a local terminal, so that you can copy/paste the commands below without replacing anything):

SCALA_VER_BASE="2.12.16"
SCALA_VER_SUFFIX=""
SCALA_SHA=c850a83a72e6514cc7e55b2c1bf01e27c0e028a3
DIST_SHA=26ada7c9d7feb71497878950b2c55549d5793772
SCALA_VER="$SCALA_VER_BASE$SCALA_VER_SUFFIX"

Key links:

• scala/scala milestone: https://github.com/scala/scala/milestones/2.12.16
• scala/bug milestone: https://github.com/scala/bug/milestones/2.12.16
• scala/scala-dev milestone: https://github.com/scala/scala-dev/milestones/2.12.16
• Discourse topic: https://contributors.scala-lang.org/t/scala-2-12-16-release-planning/5692
• release notes draft: 2.12.16 release notes draft #810
• release: https://github.com/scala/scala/releases/tag/v2.12.16

N weeks before the release

• Wind down PR queue. There has to be enough time after the last (non-trivial) PR is merged and the next phase. The core of the eco-system needs time to prepare for the final!
• Triage scala/bug and scala/scala-dev tickets
• Create next scala/scala milestone, move the magical "Merge to 2.12.x" description to it (so Scabot uses it as default for new PRs), move pending PRs
• Create next scala/bug milestone, move pending issues
• Create next scala/scala-dev milestone, move pending issues
• Check PRs assigned to the milestone, also check WIP
• Announce expected release date and current nightly "release candidate" (nightly sha-mangled version) at https://scala-ci.typesafe.com/artifactory/scala-integration/ on https://contributors.scala-lang.org/c/announcements
• Also notify Scala Center advisory board members of the upcoming release, so they can help test if they want (Seth can handle this, if asked)

Release announcement / notes

• Notify community on https://contributors.scala-lang.org/c/announcements
• Review merged PRs, make sure release-notes label is applied appropriately
• PRs with release-notes label must have excellent title & description (title will be pasted literally in release note bullet list)
• Draft release notes (PR and self-merge, so others can comment there rather than on the commits)
  • Starting point: gh api --paginate -X GET search/issues -f q='repo:scala/scala is:pull-request is:merged milestone:2.12.16 label:release-notes' -q '.items[] | " * \(.title) ([#\(.number)](\(.html_url)) by [@\(.user.login)](\(.user.html_url)))"'
• On contributors thread, link to release note file and request feedback

N days before release

• Announce no more PRs will be merged unless last-minute regressions are found. Re-iterate current nightly sha version for testing.
• Community build
  • JDK 8: https://scala-ci.typesafe.com/view/scala-2.12.x/job/scala-2.12.x-jdk8-integrate-community-build/7436/
  • JDK 11: https://scala-ci.typesafe.com/view/scala-2.12.x/job/scala-2.12.x-jdk11-integrate-community-build/2476/
  • JDK 17: https://scala-ci.typesafe.com/view/scala-2.12.x/job/scala-2.12.x-jdk17-integrate-community-build/504/
• Windows build on GitHub Actions: https://github.com/scala/scala/actions/runs/2300126473
• JDK 17 build on Travis-CI (cron job): https://app.travis-ci.com/github/scala/scala/builds/250447279
• Check any merged PRs accidentally assigned to the next milestone in this branch, and re-assign them to this milestone
• Merge in any older release branch
• Check module versioning (is everything in versions.properties up to date?)
  • including make sure the version of scala-asm we're using is using latest ASM
• On major release, bump PickleFormat version
• Close the scala/scala and scala/bug milestones

Point of no return

Once sufficient time for community testing has passed, it's time to cut the release!

What is "sufficient" time? A week is a bare minimum. Two weeks is a better "normal" amount. We should also respect requests from Scala Center advisory board members, if they explicitly ask for additional testing time. (In the past, we sometimes only waited a day or two, but this was overly optimistic in presuming that people had been testing nightlies all along.)

Be mindful of others' schedules; even minor releases make work downstream (for Scala.js and Scala Native, for the Scala 3 team, for compiler plugin authors, and so on). And a botched release might make unexpected work for ourselves as well as for others. So it's better not to release on a Friday or even a Thursday, or too close to a major holiday. And it's best to release while everyone in both America and Europe is awake. (First thing in the morning in America is a good choice.)

• Make sure there are no stray staging repos on Sonatype
• Trigger a custom build on travis
  • Select the correct branch
  • Custom config: before_script: export SCALA_VER_BASE=$SCALA_VER_BASE SCALA_VER_SUFFIX=$SCALA_VER_SUFFIX
  • Check the build status on https://github.com/scala/scala/commits/2.12.x
  • Check that the scala/scala job also triggered a following scala/scala-dist job: https://app.travis-ci.com/github/scala/scala-dist/builds/?
  • Create the scala/scala tag locally: git tag -s -m "Scala $SCALA_VER" v$SCALA_VER $SCALA_SHA
  • Create scala-dist tag locally: git tag -s -m "Scala $SCALA_VER" v$SCALA_VER $DIST_SHA
  • Note the repos to be promoted after tag is cut (see travis log)
    • https://oss.sonatype.org/content/repositories/orgscala-lang-3056
    • https://oss.sonatype.org/content/repositories/orgscala-lang-3057
    • https://oss.sonatype.org/content/repositories/orgscala-lang-3058
• Sanity check jar/pom
  • https://oss.sonatype.org/content/repositories/staging/org/scala-lang/scala-compiler/$SCALA_VER/
  • in particular, if the release was staged multiple times, double check that https://oss.sonatype.org/content/repositories/staging/ has the files from the most recent build
• Check that JARs haven't mysteriously bloated — compare sizes to previous release. We have no other backstop for this.
• Remember, tags are forever, so are maven artifacts (even staged ones, as they could end up in local caches) and S3 uploads (S3 buckets can be changed, but it can takes days to become consistent)
• Push scala/scala tag: git push https://github.com/scala/scala.git v$SCALA_VER
• Push scala/scala-dist tag: git push https://github.com/scala/scala-dist.git v$SCALA_VER
• Trigger two scala-dist jobs on travis (https://app.travis-ci.com/github/scala/scala-dist) with custom config. must use full-length SHAs!
  • before_script: export version=$SCALA_VER scala_sha=$SCALA_SHA mode=archives: https://app.travis-ci.com/github/scala/scala-dist/builds/251673574
  • before_script: export version=$SCALA_VER scala_sha=$SCALA_SHA mode=update-api: https://app.travis-ci.com/github/scala/scala-dist/jobs/572807191
  • Promote staging repos: st_stagingRepoPromote [scala-repo], st_stagingRepoPromote [modules-repo] (or use oss.sonatype.org web UI)

Check availability

• Check release on sonatype: https://oss.sonatype.org/content/repositories/releases/org/scala-lang/scala-compiler/$SCALA_VER/
• Check the release on maven central: https://repo1.maven.org/maven2/org/scala-lang/scala-compiler/$SCALA_VER/

When everything is on maven central

• Prepare PR to https://github.com/scala/scala-lang/ (using scala/make-release-notes which requires a staged release and a pushed tag)
  • download/index.md
  • _config.yml (update devscalaversion or scalaversion)
  • index.md (update currentScalaVersion)
  • add Scala 2.12.16 scala-lang#1391
• Prepare PR to https://github.com/scala/docs.scala-lang/
  • api/all.md, _config.yml, _overviews/jdk-compatibility/overview.md
  • also consider updating https://docs.scala-lang.org/overviews/jdk-compatibility/overview.html
  • add Scala 2.12.16 docs.scala-lang#2420
• Pre-announce the release on https://contributors.scala-lang.org/c/announcements
• On major releases only: (manually) update the current symlink for the API docs
  • https://github.com/scala/scala-dist/blob/2.12.x/scripts/jobs/release/website/update-api#L15
• Check that the API docs are published
  • https://www.scala-lang.org/api/ should have new version
    • https://www.scala-lang.org/api/2.12.16/
  • if they don't show up, possible troubleshooting steps include:
    • review the two scala-dist job logs to make sure that
      • the first one appears to have succeeded putting files in /home/linuxsoft/archives/scala/api on chara.epfl.ch
      • the second one appears to have succeeded in updating the symlink (from 2.1x.y to $SCALA_VER)
    • ssh to chara.epfl.ch and poke around to see if things are where they should be
      • if you don't have the credential for this locally but you are able to bring jenkins-worker-publish up at ssh jenkins-worker-publish, then from there you can ssh -i ~/.ssh/jenkins_lightbend_chara [email protected]
    • see if https://scala-webapps.epfl.ch/jenkins/view/All/job/production_scala-lang.org-scala-dist-archive-sync/ has run a job yet to sync the changes into production
      • if not, you can manually trigger a job. Seth has access to do that, probably others on the team do too. if we get stuck, Fabien can help

Prepare downstream

• Create PR to add/update spec links on scala-lang.org (example: update spec links and advisements scala-lang#1050)
• build and release scala-collection-compat and other modules (or open tickets asking that the maintainers do so)
  • this work has moved to https://github.com/scala/make-release-notes/blob/2.13.x/projects-2.13.md
• if it's a 2.12.x release, publish macro paradise for the new version
• Open tickets in these repos, requesting publishing:
  • typelevel/kind-projector
  • scalameta
  • scalafix
  • scoverage
  • silencer
  • wartremover
  • acyclic
  • Ammonite
  • (Lightbend) lightbend/genjavadoc

Wait for downstream

Before proceeding any further, wait for the ecosystem to catch up.

• Downstream publishing:
  • Wait for Scala.js to support the new release
  • Wait for Scala Native to support the new release
  • Wait for scalameta to publish
  • Wait for scalafix to publish
  • Wait for Metals to publish
  • Wait for kind-projector to publish
  • Wait for scoverage to publish
• Downstream signoffs:
  • Wait for the Scala Center to sign off (Julien)
  • Wait for VirtusLab to sign off (Krzysztof)

We have promised to wait 48 non-weekend hours, minimum.

If there are delays downstream, at some point it may make sense to go ahead and announce anyway, since news of the release will already be spreading in the community.

Announcements

• On GitHub, use "Create release from tag" button and add release notes
  • https://github.com/scala/scala/releases/tag/v$SCALA_VER
• Merge the scala-lang PR and the docs.scala-lang.org PR
  • wait for them to arrive on the websites and make sure they look okay
    • if the scala-lang changes don't show up, possible troubleshooting steps include:
      • see if https://scala-webapps.epfl.ch/jenkins/view/All/job/production_scala-lang.org-builder/ has run a job yet to actually publish the changes
      • see note above about permissions to trigger a job
• Scala Users discourse https://users.scala-lang.org
• Tweet from @scala_lang
• Discord: link to release notes in #announcements channel
  • consider also saying something in #scala-contributors channel
• Unblock the release in Scala Steward by PRing an update to default.scala-steward.conf
• Add the release to SDKMAN
  • as per the documentation at https://sdkman.io/vendors
  • URL provided must be in .zip format, .tgz doesn't work
  • sample command: curl -X POST -H "Consumer-Key: xxx" -H "Consumer-Token: xxx" -H "Content-Type: application/json" -H "Accept: application/json" -d '{"candidate": "scala", "version": "2.12.14", "url": "https://downloads.lightbend.com/scala/2.12.14/scala-2.12.14.tgz"}' https://vendors.sdkman.io/release
  • replace both xxxs with the credential information provided to Seth by Marco Vermeulen (marco at sdkman dot io)
  • test afterwards with sdk list scala and sdk install scala <version> (these should work immediately once the POST succeeds)
  • to correct mistakes, PATCH and DELETE are also available
  • broadcast the addition via the SDKMAN twitter account
    • sample command: `curl -X POST -H "Consumer-Key: xxx" -H "Consumer-Token: xxx" -H "Content-Type: application/json" -H "Accept: application/json" -d '{"candidate": "scala", "version": "2.12.14", "url": "https://github.com/scala/scala/releases/tag/v2.12.14"}' https://vendors.sdkman.io/announce/struct
• Announce on https://reddit.com/r/scala
• ask Seth to announce on #scala IRC

Afterwards

• Scala 3: open PR updating version:
  • two places to update:
    • project/Build.scala
    • community-build/community-projects/stdLib213 (after updating https://github.com/dotty-staging/scala to include recent commits)
  • https://github.com/lampepfl/dotty/pulls
• Scastie: open PR adding new version (modeled on Add support for Scala 2.13.7 scalacenter/scastie#538)
  • note that the PR won't be mergeable until kind-projector has published; and if kind-projector's version number has changed, ScalaTarget.scala will need updating
• If it's a major release:
  • Update latestSpecVersion in spec/_config.yml on the old branch, so that spec is marked as no longer current
  • Ditto for the nightly build and spec links in _data/footer.yml and _data/doc-nav-header.yml on docs.scala-lang.org
• Create PR to update https://github.com/lightbend/lightbend-technology-intro-doc/blob/master/docs/modules/getting-help/pages/build-dependencies.adoc
• (Lightbend) Fortify:
  • Publish scala-fortify-plugin
  • Update scala-fortify
  • Update scala-fortify-docs
• (Lightbend) Update whatever we replaced WhiteSource with, if anything?
• (Lightbend) Notify eng-updates
• Update https://contributors.scala-lang.org thread
• Create a scala/scala PR to:
  • update starr.version in /versions.properties
  • update Global / baseVersion in /build.sbt
  • update mimaReferenceVersion in /project/MimaFilters.scala
  • clear out mimaFilters in /project/MimaFilters.scala, except the one(s) labeled "KEEP"
  • spec/_config.yml, if it's a major release
  • re-STARR onto 2.12.16 scala#10043

You're done!

• Close this ticket and close the scala-dev milestone