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releasing.md

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Releasing

These instructions describe how to cut a new release.

You should always start from this doc when initiating a release.

MDC follows the "git flow" style of development, where the default branch is called develop. stable (instead of the traditional master) is reserved for releases. The develop branch is periodically copied to a release candidate, tested, and then merged into stable, which serves as the stable "vetted" branch.

A note on the role of the release engineer

Each release is driven by a single release engineer, who is also a Googler. The release engineer is expected to do the following, in order of priority:

  • Do not break Google.
  • Cut a release early in the working calendar week.
  • Land a release at least once every calendar week.
  • (Optional) Share something new with the team while you're waiting for tests to pass.

If something is stopping the release engineer from achieving any of the above goals, the culprit code should be removed immediately from the release.

Importantly: do not block the cutting of the weekly release on a PR or a piece of functionality you'd like to land. If your PR hasn't landed by the time the release is cut, it's not making it into that week's release. If your PR is important, cut a hotfix release in addition to the typical weekly release.

If you are not able to cut a release Wednesday morning, cut it Tuesday evening before you leave the office.

Please post regular updates about the status of the release to the team's chat room. This helps inform the team of the status of the release, and also encourages team problem solving in the event that something is stuck. At minimum, the following inflection points should be noted:

  • The release is being initiated.
  • Internal testing of the release has begun.
  • Internal testing of the release has ended.
  • The release has been submitted internally.
  • The release has been published to CocoaPods.

For Googlers, also read go/mdc-release-engineering for additional details.

Before you start

First time setup

Install brew, sourcekitten, and git-lfs:

brew install sourcekitten
brew install git-lfs

Please follow using git-lfs instructions if you have already cloned the repository.

Verify that xcode-select is pointing to an Xcode installation directory:

xcode-select -p

# Example output:
# /Applications/Xcode.app/Contents/Developer

If not, select the Xcode you have installed. For example:

sudo xcode-select --switch /Applications/Xcode.app

Create a clean clone

Make sure you are working from a direct clone of the main Git repository. The scripts involved assume that the remote "origin" is the actual repository and not your fork. Since most contributors will be working day-to-day with a fork, consider creating a separate clone just for releases.

git clone [email protected]:material-components/material-components-ios.git mdc-ios-release
cd mdc-ios-release

Configure the merge strategy for .gitattributes

We have two different versions of .gitattributes in the develop and stable branches. To avoid conflicts (or accidental merges) between the two branches, we define a custom merge strategy just for that file. After cloning the repository, be sure to run this command:

git config merge.gitattributes.driver true

Cutting and testing the release

Our entire release process is encoded into the release script in the scripts/ directory. Read the tool's readme to learn more about the tool.

Cut a release branch

Run the following command to cut a release:

scripts/release cut

Note: if for some reason cut fails, first ensure that nobody else is in the middle of cutting a release by visiting the repo and verifying that a release-candidate does not already exist because aborting the release will delete the remote release candidate. If that isn't the case, then please run scripts/release abort and try again.

You will now have a local release-candidate branch, a new section in CHANGELOG.md titled "release-candidate", and the release-candidate branch will have been pushed to GitHub.

Hotfixing

If you need to cut a hotfix release, run the following command instead:

scripts/release cut --hotfix

A hotfix release is like a regular release, but its scope is limited specifically to the fix. Hotfix release candidates start from origin/stable rather than origin/develop.

If the hotfix is to fix a regression or a problematic commit in a recent release, the ideal path forward is to revert that commit using the git revert <commit-hash> command and opening a PR with that change to the develop branch. After that PR is merged, you should cherry-pick the revert commit into the release-candidate branch: git cherry-pick <commit-hash>.

Other than the steps above regarding hotfixing, the entire release process stays the same.

Create a Pull Request for the Release Branch

If you have not clicked the release candidate pull request comparison link provided in the script do so now.

At this point you should also create the initial Release Candidate pull request using the URL that the cut script generated.

Name the Pull Request title "{WIP} Release Candidate." until you are able to provide the version as the title.

Add the group material-components/release-blocking-clients to the pull request's reviewers. This is the mechanism by which release-blocking clients are notified of a new release.

Do not use GitHub's big green button to merge the approved pull request. Release are an exception to our normal squash-and-merge procedure.

Verify CocoaPods podspec and trunk access

Send our local podspec through the CocoaPods linter:

pod lib lint MaterialComponents.podspec --skip-tests --allow-warnings

CocoaPods publishes a directory of publicly available pods through its trunk service. Note: Ensure that you can push the podspec later by checking for MaterialComponents in your list of available Pods when you:

pod trunk me

If this fails or MaterialComponents is not listed register an account and session.

Start internal testing

You can now start the internal release testing process documented at go/mdc-releasing.

Resolve any failures

Push release-candidate to GitHub with git push origin release-candidate as you make changes. This allows other people and machines to track the progress of the release.

Make any necessary changes

You, or clients, may find problems with the release that need fixing before continuing. You have two options for making those changes:

  1. If the change does not touch library code and is trivial, then you can make the change directly on the release candidate branch.
  2. If the change touches library code, is non-trivial, or you just want a second opinion, create a pull request targeting release-candidate and get it reviewed.

Note that in both cases, changes made to the release candidate branch will be merged back into develop at the end of the release.

Determining the new version and drafting the release notes

The two most important bits of metadata about a release is the new version number and the release notes. While we have tooling to help, your job is to make sure these are correct. If you're not familiar with MDC's version number policy, please review it now.

To figure out the release number you will need to examine the release's changes.

You have several tools available for deciding if a release is major, minor, or a patch.

Review the API diff

CHANGELOG.md automatically includes the latest set of public API changes as part of the cut command. Inspect the API changes to get a quick sense of whether there might be an API-breaking change.

  1. If any part of a public API is deleted or changed, then this release is a major release.
  2. If any public API's nullability annotations have changed then this release is a major release.
  3. Otherwise, if any public APIs added, then this release is a minor release.
  4. Otherwise, this release might still be a bug fix release.

New Features / Top Level Description

In the "New Features" sub-category generated by the API diff tool, please provide more detail as to what is new in the release, also providing examples on how to use the added public API properties/methods. For instance if you have added the method setShadowWidth: to MDCCard an example usage would be:

let card = MDCCard()
card.setShadowWidth(10)

In the top level description please provide a sentence explaining the overall release. Something along the lines of: "This minor/major/patch release includes X and Y along with some Z."

Verify API changes

While we do primarily lean on the api_diff tool to call out API diffs, it isn't perfect. For each API change, open the source at the latest checkout and verify that the API change does, in fact, reflect the change that occurred.

Adjust the API diffs in CHANGELOG.md based on your visual inspection of the code.

Commit the final results to your branch.

git add CHANGELOG.md
git commit -m "Hand-modified CHANGELOG.md API diff."
git push origin release-candidate

Identify visual changes

We do not presently have an automated way to identify visual changes between releases. See GitHub issue #290 for a discussion on the topic.

[Optional] Sanity check: inspect the changes

Diff just the components

The final sanity check is to visually inspect the diff.

If you have configured Git with a GUI diff tool (git difftool) like Kaleidoscope, then you can add --use_diff_tool to scripts/release diff below.

Generate a list of component public header changes:

scripts/release headers

Show changes to component headers:

scripts/release diff components/*/src/*.h

Show all changes to components:

scripts/release diff components/*/src/

Diff everything

Show all changes that are part of this release:

scripts/release diff

Classify the release type

You should now be able to identify the release type and its new version number. Bump the release (change the version number everywhere):

scripts/release bump <major.minor.patch>

Commit the results to your branch:

git commit -am "Bumped version number to $(scripts/print_version)."
git push origin release-candidate

Update the PR title to the release version. The format is typically "vX.Y.Z" (e.g., v72.0.1). Once this is done, send the PR out for review. Add "material-components/core-ios-team" to the list of Reviewers. Also add anyone else you think might need to review specific changes in the release candidate.

Consider running scripts/release notes again

Run scripts/release notes again and copy paste it into the CHANGELOG.md after ## Changes if you

  • cherry picked a change to add it to the release or
  • reverted any commit to rollback any PR.

Testing with release-blocking clients

Before you can merge the release branch into either develop or stable you must get the release go-ahead from the following clients:

  • Google: must verify that the release branch passes all internal tests. If you are a Googler, see the internal "mirroring" document for further instructions. Notably you must not continue this releasing process until the internal synchronization CL has been tested.
           |\___/|
          (,\  /,)\
          /     /  \       DRAGON SAYS HALT:
         (@_^_@)/   \      READ THE ABOVE SECTION BEFORE CONTINUING.
          W//W_/     \     DO NOT MERGE OR CUT ANY RELEASES UNTIL
        (//) |        \    YOU'VE DONE SO.
      (/ /) _|_ /   )  \
    (// /) '/,_ _ _/  (~^-.
  (( // )) ,-{        _    `.
 (( /// ))  '/\      /       \
 (( ///))     `.   {       }  \
  ((/ ))    .----~-.\   \-'    ~-__
           ///.----..>   \ \_      ~--____
            ///-._ _  _ _}    ~--------------

Merge the release candidate branch

Once the release-candidate has passed all "Required" GitHub presubmit tests and all internal presubmit tests, you may merge the release into the develop and stable branches using the release script.

Do not use GitHub's big green button to merge the approved pull request. Release are an exception to our normal squash-and-merge procedure.

# Did you listen to the dragon?
#
# Do not run this until all release-blocking clients have given the go-ahead.
# Ensure that you've checked off every item in the commit message's checklist.
#
scripts/release merge <version>

Once you've resolved any merge conflicts your local develop and stable branches will both include the latest changes from release-candidate.

You must merge to both develop and stable. This is the mechanism by which we ensure that stable matches develop.

Push the branches to GitHub

You can now push the merged release candidate to GitHub so that you can complete the final synchronization within Google.

git push origin stable develop

You can now sync to the desired stable release. go/mdc-releasing#re-run-the-import-script-against-githubstable. Once you've submitted the internal CL, continue below to tag and publish the release.

Publish the official release

Have all release-blocking clients given the go-ahead? Do not create the official release until all release-blocking clients are ready. Otherwise you might publish a release that isn't actually stable.

You can now publish the release to GitHub:

scripts/release publish <version>

Publish to Cocoapods

git checkout stable
pod trunk push MaterialComponents.podspec --skip-tests --allow-warnings

Coordinate with release-blocking clients to finish work

Any work that was started by the Release-blocking clients (dragon) step above may need to be finalized.

Also follow last instructions in the internal release instructions