Core Library policies
This page describes a proposed process for maintaining the Core libraries.
Core libraries are particularly important, and as such we apply some (lightweight) policies to their development. In the past we used the Library_submissions process, but that was deemed to hamper productivity too much. The new policy puts more emphasis on leadership and empowers individual maintainers to make changes, while still allowing the community to make feedback, contributions, and proposals.
Non-core libraries are, of course, managed by their own authors/maintainers (named in their .cabal file), using whatever policies those maintainers see fit. [Note: arguably the policies below might usefully be applied to all libraries embodied in the Haskell Platform, but that is a question for the HP team.]
What are the Core Libraries?
The following packages form the core libraries. They are a subset of the packages in the Haskell Platform, and define basic APIs that are expected to be available in any Haskell implementation:
Policies for development, and community involvement
- Each core package has a named maintainer, or small group of maintainers, who have commit access to the package.
- The maintainers are trusted to decide what changes to make to the package, and when. They are strongly encouraged to follow the guidance below, but the general principle is: the community offers opinions, but the maintainers decide.
- Third parties are encouraged to make proposals for API changes by sending them to the maintainers (CC'ing the libraries mailing list). Proposals that are accompanied by patches (preferably with tests and documentation), and have widespread support, should normally be accepted by the maintainer.
- Third parties can submit non-API changes as patches directly to the maintainer (CC'ing the libraries mailing list).
- Commit logs will be sent to a public mailing list, or otherwise made easily available (e.g. via github), so that the community can keep an eye on changes and comment.
Guidance for maintainers:
- Every API change should be described precisely in the commit log.
- API changes should be discussed on the libraries mailing list prior to making the change. The maintainer still has ultimate say in what changes are made, but the community should have the opportunity to comment on changes.
- Typically, the maintainer would specify the change, explain why they advocate it, and give a deadline for comments. The maintainer is trusted to use his or her judgement in responding to comments and adapting the proposal where appropriate. However, unaminity (or even a majority) is not required.
- Backwards compatibility is important to many users. API changes are expected to retain backwards compatibility wherever possible. However, from time to time we may decide to have major revisions which are explicitly not backwards compatible; in these cases we may try to make the previous version of the package available concurrently, as in the base-3/base-4 switchover.
- Responsiveness. Third parties submitting proposals to the maintainer of a library can expect a timely and thoughtful response. The more effort the proposer invests (eg by constructing a patch rather than making an off-the-cuff suggestion) the more consideration s/he can reasonably expect.
Libraries maintained by the GHC team are subject to the GHC validation policy - patches will be tested for validation before committing. Those packages not maintained by the GHC team will probably have a GHC lagging mirror repository that is subject to validation.
Creating a proposal
In order to ensure we have something concrete to discuss, please follow the following guidelines:
- Currency. Make your changes against a copy of the master branch of the relevant library, and make sure it compiles.
- Portability. Code should be portable. If it is not portable, reasons should be given. At the very least ensure the code runs in Hugs and GHC, and on Windows and Linux.
- Style. Follow the conventions in the library you are modifying.
- Documentation. It must include valid Haddock documentation.
- Tests. Code should ideally also come with suitable tests for the testsuite. There's currently some disagreement about what this means. Discussion of where we may want to head is in the library tests page.
Submitting the proposal
- Patch. Create a darcs or git patch (depending on what sort of repo the library lives in) of your change using darcs record or git commit -a, including a rationale for the change. Save the patch to a file, using darcs send --output or git format-patch.
- Submission. Start a new thread on the email@example.com mailing list (which you need to subscribe to before posting), with a subject beginning "Proposal:". Include a description of the change and the rationale, and attach the patch. You may wish to include a pointer to updated Haddock documentation, if relevant. You must also include a deadline for the discussion period; it must allow at least 2 weeks for discussion, but you may allow more - particularly if many people are likely to be away during the next 2 weeks. If discussion is still ongoing at the deadline, the discussion period can be extended.
If someone has done all this, they are entitled to expect feedback; silence during the discussion period can be interpreted as consent.
At the end of the discussion period
- Determine whether consensus for the change was reached. A deeply held disagreement at this point may require some form of governance (voting, dictatorship, etc). This should be a rare event.
- If consensus was achieved, file a ticket on the GHC trac, attaching the (revised if necessary) patch. As well as the description and rationale, include a link to the discussion in the mailing list archives, as well as a summary of the conversation (the summary is needed for anyone wondering about the change later: it's not reasonable to point people at a 50-message thread (but please do include a link to the thread in the list archives too, so that people can review it if they wish)).
Here is an example of how to summarise a successful submission.
The following packages are also listed as maintained by
firstname.lastname@example.org, but are not in fact maintained by the community as a whole. We plan to clarify the maintainership of these packages shortly.
These packages are not expected to undergo API changes in the future. The code will be maintained by the GHC team.
These packages match the appropriate language standard, and as such cannot change independently. The code is maintained by the GHC team.
These packages in fact have maintainers, in most cases the GHC team:
These packages are orphaned, and are looking for a maintainer: