Release 2.12.12

[retronym]

For every Scala release, make a copy of this file named after the release, and expand the variables.
Ideally this should become a script you can run on your local machine. The only missing piece is programmatic triggering of travis jobs with custom config.

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

• SCALA_VER_BASE="2.12.12"
• SCALA_VER_SUFFIX=""
• SCALA_SHA=cbe6ade1744bb316a63a07b07d3bf448590ad2cd
• DIST_SHA=2d9200053dad901dbda2789d61057670c2cd757b
• SCALA_VER="$SCALA_VER_BASE$SCALA_VER_SUFFIX"

Key links:

• scala/scala milestone: https://github.com/scala/scala/milestone/85
• scala/bug milestone: https://github.com/scala/bug/milestone/106
• scala/scala-dev milestone: https://github.com/scala/scala-dev/milestone/35
• Discourse topic: https://contributors.scala-lang.org/t/coming-soon-scala-2-12-12/4371

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 2.13.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 (to be published once GitHub tag is pushed)
  • note that GitHub release notes drafts can only be viewed by committers, so use a gist to draft the notes, so the gist can be shared with the community
• On contributors thread, link to release note gist 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/job/scala-2.12.x-integrate-community-build/5852/
  • JDK 11: https://scala-ci.typesafe.com/job/scala-2.12.x-jdk11-integrate-community-build/1317
• Windows Jenkins job
  • if there isn't already a nightly run on the exact right SHA (check the log), manually trigger one
  • https://scala-ci.typesafe.com/job/scala-2.12.x-integrate-windows/1796/
• 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?)
• On major release, bump PickleFormat version
• Close the scala/scala and scala/bug milestones

Point of no return

Once sufficient time has passed since last merged PR, it's time to cut the release!

How long we wait depends on what kind of release it is. For a major release, it might be 1-2 weeks, to give core projects time to try out the preceding release candidate and/or the current candidate nightly. For point releases, assuming we've given the community ahead-of-time warning and kept them appraised of progress on the Discourse thread, and assuming the last changes merged seem sufficiently safe, we might build the next day.

• Make sure there are no stray staging repos on sonatype
• Trigger a custom build on travis: https://travis-ci.org/github/scala/scala/builds/707479294
  • 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://travis-ci.org/github/scala/scala-dist/builds/707482649
  • 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 $DIST_SHA
  • Note the repos to be promoted after tag is cut (see travis log)
    • Four staging repos rather than the expected 2. library/reflect/compiler are segregated, not sure why...
    • https://oss.sonatype.org/content/repositories/orgscala-lang-2147
    • https://oss.sonatype.org/content/repositories/orgscala-lang-2148
    • https://oss.sonatype.org/content/repositories/orgscala-lang-2149
    • https://oss.sonatype.org/content/repositories/orgscala-lang-2150
• Sanity check jar/pom
  • https://oss.sonatype.org/content/repositories/staging/org/scala-lang/scala-compiler/$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$SCALA_VER
• Add release notes to https://github.com/scala/scala/releases/tag/v$SCALA_VER
• Push scala/scala-dist tag: git push https://github.com/scala/scala-dist.git v$SCALA_VER
• Trigger two scala-dist jobs on travis (https://travis-ci.org/scala/scala-dist) with custom config. must use full-length SHAs!
  • before_script: export version=$SCALA_VER scala_sha=$SCALA_SHA mode=archives: https://travis-ci.org/github/scala/scala-dist/builds/707533902
  • before_script: export version=$SCALA_VER scala_sha=$SCALA_SHA mode=update-api: https://travis-ci.org/github/scala/scala-dist/builds/707533982
• 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): Announce Scala 2.12.12 scala-lang#1151
  • documentation/api.md
  • download/index.md
  • _config.yml (update devscalaversion or scalaversion)
• Prepare PR to https://github.com/scala/docs.scala-lang/
  • api/all.md, _config.yml :
• make sure the draft release notes are on GitHub tag: https://github.com/scala/scala/releases/tag/v$SCALA_VER
• Pre-announce the release on https://contributors.scala-lang.org/c/announcements
• On 2.13.0 only: (manually) update the current symlink for the API docs
  • https://github.com/scala/scala-dist/blob/2.13.x/scripts/jobs/release/website/update-api#L15
• Check that the API docs are published
  • http://www.scala-lang.org/api/$SCALA_VER/
  • https://docs.scala-lang.org/api/all.html ?
• 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

Modules

• 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
  • Bump to Scala 2.12.12 scalamacros/paradise#124

Announcements

• Scala Users discourse https://users.scala-lang.org -> https://users.scala-lang.org/t/scala-2-12-12-is-available/6365
• add a reply on the same https://contributors.scala-lang.org thread where you announced that the release process was starting
• Tweet from @scala_lang
• https://gitter.im/scala/scala
  • if you feel like it, say something in https://gitter.im/scala/contributors too
• ask Seth to announce on #scala IRC

Afterwards

• Check the release on maven search (may take a few hours):
  • https://search.maven.org/#search%7Cga%7C1%7Cg%3Aorg.scala-lang%20v%3A$SCALA_VER
• Create PR to add/update spec links on scala-lang.org (example: update spec links and advisements scala-lang#1050)
• Create a scala/scala PR to update versions.properties and the baseVersion in build.sbt. -> Bump to Scala 2.12.12 scala#9115
  • If it's a major bump, also update MiMa base version, exclusion filters, and spec/_config.yml.
• If it's a major bump:
  • 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
• Consider updating https://docs.scala-lang.org/overviews/jdk-compatibility/overview.html
• (Lightbend) Publish scala-fortify-plugin
• (Lightbend) Update WhiteSource
• (Lightbend) Notify eng-updates
• Close this ticket and close the scala-dev milestone

[retronym]

Draft release notes:

Highlights

This release adds compiler support for scala-async and backports substantial performance improvements to collections.

• The compiler now includes a phase that performs the transformation for the async/await DSL for working with Scala Futures.
  This transform is based on the macro implementation in scala-async but has been substantially rewritten to fix some longstanding bugs, reduce the overhead of compilation and simplify the extension points for third party effect systems.
  scala-async 1.0.0 will be released shortly building atop this phase. (#8816)
• immutable.{TreeSet, TreeMap} are now based on a backport of the 2.13.x implementation. (#8749)
• The builders for immutable.{HashSet, HashMap} are more efficient -- they now use mutation during reducing memory churn. (#8726) (#8726)

Further highlights

• Minor improvements to compiler performance. The allocation rate of the compiler is reduced by 10%.

This is not a complete list of changes. For that, see all merged PRs and all closed bugs.

Compatibility

As usual for our minor releases, Scala 2.12.12 is binary-compatible with the whole Scala 2.12 series.

Contributors

A big thank you to everyone who's helped improve Scala by reporting bugs, improving our documentation,
spreading kindness in discussions around Scala, and submitting and reviewing pull requests! You are all magnificent.

This release was brought to you by 13 contributors, according to git shortlog -sn --no-merges v2.12.11..v2.12.12. Thank you Jason Zaugg, Mike Skells, Lukas Rytz, Harrison Houghton, Adriaan Moors, Stefan Zeiger, Dale Wijnand, Seth Tisue, A. P. Marki, Eugene Yokota, NthPortal, Georgi Krastev and Martijn Hoekstra.

Thanks to Lightbend for their continued sponsorship of the Scala core team’s efforts. Lightbend offers commercial support for Scala.

Scala 2.12 notes

The release notes for Scala 2.12.0 have important information applicable to the whole 2.12 series.

Obtaining Scala

Scala releases are available through a variety of channels, including (but not limited to):

• Bump the scalaVersion setting in your sbt-based project
• Download a distribution from scala-lang.org
• Obtain JARs via Maven Central