Contributing Guidelines

Contributions are very welcome! To hack on the github version, clone the repository. You can use cabal:

./scripts/start-sandbox.sh # Initialize the sandbox and add-source the packages
./scripts/test-all.sh      # Run all the tests

Or stack:

stack setup                    # Downloads and installs a proper GHC version if necessary
stack build --fast --pedantic  # Install dependencies and build packages
stack test                     # Run all the tests

Or nix:

./scripts/generate-nix-files.sh   # Get up-to-date shell.nix files

To build the docs, see doc/README.md.

General

Some things we like:

Explicit imports
Upper and lower bounds for packages
Few dependencies
-Werror-compatible (7.8, 7.10 and 8.0)

Though we aren't sticklers for style, the .stylish-haskell.yaml and HLint.hs files in the repository provide a good baseline for consistency.

Important: please do not modify the changelog files nor the versions of the servant packages you are sending patches for. We take care of this before every release and do it uniformly for all the servant packages, so there's no need to worry about this for your pull requests.

PR process

We try to give timely reviews to PRs that pass CI. If CI for your PR fails, we may close the PR if it has been open for too long (though you should feel free to reopen when the issues have been fixed).

We require two +1 from the maintainers of the repo. If you feel like there has not been a timely response to a PR, you can ping the Maintainers group (with @haskell-servant/maintainers).

New combinators

We encourage people to experiment with new combinators and instances - it is one of the most powerful ways of using servant, and a wonderful way of getting to know it better. If you do write a new combinator, we would love to know about it! Either hop on #servant on freenode and let us know, or open an issue with the news tag (which we will close when we read it).

As for adding them to the main repo: maintaining combinators can be expensive, since official combinators must have instances for all classes (and new classes come along fairly frequently). We therefore have to be quite selective about those that we accept. If you're considering writing a new combinator, open an issue to discuss it first! Or contribute it to the servant-contrib repository. You could release your combinator as a separate package, of course.

New classes

The main benefit of having a new class and package in the main servant repo is that we get to see via CI whether changes to other packages break the build. Open an issue to discuss whether a package should be added to the main repo. If we decide that it can, you can still keep maintainership over it.

Whether or not you want your package to be in the repo, create an issue with the news label if you make a new package so we can know about it!

Release policy

We are currently moving to a more aggresive release policy, so that you can get what you contribute from Hackage fairly soon. However, note that prior to major releases it may take some time in between releases.

Reporting security issues

Please email haskell-servant-maintainers AT googlegroups DOT com. This group is private, and accessible only to known maintainers. We will then discuss how to proceed. Please do not make the issue public before we inform you that we have a patch ready.

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