The easiest way to produce a release of a GitHub-based open-source software is to tag the most recent commit on the
main with the version number at regular intervals of time or once a previously agreed milestone is reached. However, this approach to releasing would rest on the assumption that each commit at the
main branch can potentially be made into a release. We cannot provide the release-grade quality guarantees for each of the
main commits, though.
Consequently, in Dotty, we are using the method above – releasing-by-tagging – to mark release candidates (RC’s) and not the stable releases. The stable releases are also marked by a tag, but we have a procedure to assure their quality.
An RC is promoted to a stable release in one release cycle after its creation. The idea is that this way, we have one release cycle's time to examine the release candidate and find critical issues which cannot be allowed into a stable release.
If such issues are found, their fixes end up on a separate branch dedicated to that release. In one release cycle after the RC creation, the RC, along with all its subsequent fixes, is promoted to a stable release by means of tagging it.
Say we want to release the 0.14.0 version. In this section we describe the process to do so (at a glance).
- Tag the latest
0.14.0-RC1. This commit is the release candidate for the
- Create a branch from that commit called
0.14.x. This branch is intended to host the subsequent fixes to the RC for the issues that cannot be allowed in the
- Up until the next release date, if we find some issues with
0.14.0-RC1that cannot end up in the release, we push the fixes to the
- At the next release date, we release
0.14.0from the branch
0.14.x. We do so by tagging the latest commit at the
0.14.0. Some things to note here:
- At this point,
0.14.x(the branch) and
0.14.0-RC1(the tag at which
main) may differ, and the
0.14.xbranch is a more mature version of the
0.14.0is not the same as the
main. Only the commits critical for the
0.14.0release end up at
0.14.xbranch. Not all of the commits made to the
mainduring the release cycle are critical to
0.14.0. However, all of the commits from
0.14.xmust end up on the
mainbranch, so we merge
- After the
0.14.0version is released, we start the process for releasing
0.15.0– repeat this algorithm from the beginning with the version set to
0.15.0-RC1at step (1).
CI is set to automatically detect the tags of the format discussed above and perform the required release operations. Precisely, it will do two things for the release tags:
- Publish the release jars to Maven
- Create the drafts at the GitHub release page of the repository with the artefacts of the release.
The CI operation is entirely automatic provided you have tagged the release correctly. No need to do anything here.
The below guidelines are needed only to speed up things. It is no mistake if you skip this section. However, if you do things wrong here, there may be trouble. So do it only if you feel yourself confident with the release cycle and the workings of the CI.
Note that after the first stage of the release cycle (see "Publishing artifacts to Maven via CI" section of the checklist below) only three test runs are required to be run at the CI:
mainbranch's latest commit with the updated
<stable-version>tag of the stable version being released
<rc-version>tag of the RC version being released
However, you may end up with as many as 6 tasks being run. The auxiliary tasks may include:
- commit tests of the tags specified above. You may have two of these, corresponding to the two tags. You should see them appearing to have the same commit hash in the CI, but one of them will have the tag next to it and the other one will not. The tag one must remain, as the CI tasks on tags publish to maven. CI tasks on commits do not. So it is safe to cancel the task running on the commit, if the commit hash is the same as that of the tag's task commit.
- Older commit from the
mainbranch. Look for all the tasks run on the
mainbranch in the CI and see if there are more than one of these. Then, find the one testing the most recent commit of the branch. The others can safely be canceled.
Before we start the release procedure, we create an issue with a release checklist. As we go through the release, we update the checklist. To generate the checklist, run the following command:
bash <(curl -sL https://raw.githubusercontent.com/lampepfl/dotty/main/docs/docs/contributing/checklist.sh) <stable_release>
<stable_release> is the stable version being released. For example, if you are releasing
0.15.0-RC1, this variable is
14 and the command is as follows:
bash <(curl -sL https://raw.githubusercontent.com/lampepfl/dotty/main/docs/docs/contributing/checklist.sh) 14
Copy and paste the output into the release issue.
The ecosystem update section for some projects also mentions a set of criteria upon which the project is to be marked in the checklist. When the Travis build status is specified next to the project's name, it is to be understood that this build must pass after all of the other criteria of that project are checked. Note that due to caching, the label image next to the link may not reflect the real status of the build. Therefore, to verify the status, click on the link and make sure that your recent commit passes.
When no criteria is specified, common sense is to be used.
After the release is done, we document it as follows:
- On the GitHub release page, modify the release drafts created by CI. The RC draft should include notable changes introduced since the previous RC. E.g. for
0.14.0-RC1these are generated by
gren changelog -G --override -D prs --tags=0.13.0-RC1..0.14.0-RC1.
grenis available here, and before running the above command, please make sure that (1) the
originbranch points to the
lampepfl/dottyrepository and (2) the two tags mentioned in the command are pushed to the
mainbranch of that repo. Otherwise, the command won't pick up the tags.
- Create a blog article documenting the most important changes done by the release.
During the release process we ensure that various parts of the community are also prepared for the new version of Scala so that users can hit the ground running when the new release is announced. You can see an example of this here.
Note that at the same time we will also publish the
0.15.0-RC1 release. We publish two releases at the same time as per the logic outlined at the Example/At the Dotty Repo and the Model sections above: the step (5) in the algorithm outlined in the Example for the release cycle of
0.14.0 is the step (1) in the release cycle of
The following commands assume a remote tracking repository named
origin pointing to the main Dotty repository:
######## Publish the 0.14.0 stable version – end the release cycle for 0.14.0 ########
git checkout 0.14.x
# Change `val baseVersion = "0.14.0-RC1"` to `val baseVersion = "0.14.0"` in project/Build.scala
git commit -am 'Release Dotty 0.14.0'
git tag 0.14.0
git push origin 0.14.0
git checkout main
git merge 0.14.x
# Make sure the merge doesn't break anything. In doubt, create a PR to run the CL
git push origin main
######## Publish the 0.15.0-RC1 unstable version – begin the release cycle for 0.15.0 ########
# Move all the unfinished tasks from Milestone 15 to Milestone 16 on GitHub – see https://github.com/lampepfl/dotty/milestones
git checkout -b 0.15.x
# Change val baseVersion = "0.15.0" to val baseVersion = "0.15.0-RC1"
git commit -am 'Release Dotty 0.15.0-RC1'
git tag 0.15.0-RC1
git push origin 0.15.x
git push origin 0.15.0-RC1
git checkout main
# Change val baseVersion = "0.15.0" to val baseVersion = "0.16.0" - this will be the next version after `0.15.0-RC1` is promoted to `0.15.0`.
git commit -am 'Set baseVersion to 0.16.0'
git push origin main