This post describes the goals, release process, and estimated schedule for Swift 5.1.
Motivation and Goals
The primary goal of Swift 5.1 is for the language to achieve module stability.
On Apple platforms, since the ABI is now stabilized, Swift 5.1 is binary compatible with Swift 5.0, and is binary compatible with future releases of Swift.
On non-Apple platforms (such as Linux) the ABI is not yet fully stable in order to allow for more vetting. Such vetting will be particularly needed for the new platforms based on Linux.
As with Swift 5.0, we expect that majority of sources that built with the Swift 5.0 compiler will compile with the Swift 5.1 compiler. However, it is possible that a bug fix in Swift 5.1 may cause it to detect errors in code that were not detected before.
Snapshots of Swift 5.1
Downloadable snapshots of the Swift 5.1 release branch will be posted regularly as part of continuous integration testing.
Once Swift 5.1 is released, the official final builds will also be posted in addition to the snapshots.
Getting Changes into Swift 5.1
The development of Swift 5.0 required an unusual amount of focus and attention throughout the time it converged because every issue had to be evaluated for its permanent ABI impact. Consequently, Swift 5.1 has a significantly shorter development window than previous releases. This tighter time constraint is needed to ensure delivering a mature and stable 5.1 release, with stricter cutoff dates for disruptive changes.
swift-5.1-branch contains the changes that will be released in Swift
5.1. The branch will be managed as follows:
swift-5.1-branchhas already been initially cut from
masterdevelopment branch will be merged into
swift-5.1-branchuntil the final branch date.
March 18, 2019 (final branching): The
swift-5.1-branchwill have changes merged from
masterone last time. After the final branch date there will be a “bake” period in which only select, critical fixes will go into the release (via pull requests).
Some notable exceptions to this plan are indicated in the table below.
Each will merge from
swift-5.1-branch daily. The final
cutoff date for changes to each exception will extend beyond March 18
and will be announced later.
|indexstore-db||To be announced|
|sourcekit-lsp||To be announced|
|swift-corelibs-foundation||To be announced|
|swift-corelibs-libdispatch||To be announced|
|swift-corelibs-xctest||To be announced|
|swift-llbuild||April 10, 2019|
|swift-package-manager||April 10, 2019|
|swift-stress-tester||To be announed|
|swift||March 18, 2019|
Philosophy on Taking Changes into Swift 5.1
All language and API changes for Swift 5.1 will go through the Swift Evolution process. Evolution proposals should aim to be completed by the branch date in order to increase their chances of impacting the Swift 5.1 release. Exceptions will be considered on a case-by-case basis, particularly if they tie in with the core goal of the release.
Other changes (e.g., bug fixes, diagnostic improvements, SourceKit interface improvements) will be accepted based on their risk and impact.
Low-risk test tweaks will also be accepted late into the release branch if it aids in the qualification of the release.
As the release converges, the criteria for accepted changes will become increasingly restrictive.
The following repositories will have a
swift-5.1-branch branch to track
sources as part of Swift 5.1 release:
The overall management of the release will be overseen by the following individuals, who will announce when stricter control of change goes into effect for the Swift 5.1 release as the release converges:
Ted Kremenek is the overall release manager for Swift 5.1.
Ben Cohen is the release manager for the Swift Standard Library.
Please feel free to post on the development forum or contact Ted Kremenek directly concerning any questions about the release management process.
Pull Requests for Release Branch
In order for a pull request to be considered for inclusion in the release
branch after the final re-branch from
master it must include the following
Explanation: A description of the issue being fixed or enhancement being made. This can be brief, but it should be clear.
Scope: An assessment of the impact/importance of the change. For example, is the change a source-breaking language change, etc.
SR Issue: The SR if the change fixes/implements an issue/enhancement on bugs.swift.org.
Risk: What is the (specific) risk to the release for taking this change?
Testing: What specific testing has been done or needs to be done to further validate any impact of this change?
Reviewer: One or more code owners for the impacted components should review the change. Technical review can be delegated by a code owner or otherwise requested as deemed appropriate or useful.
All change going into the
swift-5.1-branch (outside changes being merged
in automatically from
master) must go through pull requests that are
accepted by the corresponding release manager.