What is stackage?

Haskell is a programming language with a large community-run library of open-source packages called Hackage. The problem is that anyone can upload anything to Hackage, and packages don't always work together, a new version of one package might break another package that depends on it. Stackage solves this by creating a curated, vetted set of packages that are tested and confirmed to work together. This repository is the hub where that curation happens. At a high level, the project maintains a list of which packages to include and rules about how they should fit together. For nightly snapshots, the system grabs the newest versions of all included packages, calculates a build plan, and verifies that everything compiles. For LTS (Long Term Support) releases, it takes the most recent build plan and carries it forward, locking major versions to keep things stable for at least three months. Once a snapshot is created, it's frozen, it won't get newer versions, only bug-fix-level updates within the same LTS line. This particular repository is aimed at package authors and maintainers who want their Haskell packages included in Stackage. To get a package in, the maintainer agrees to a maintainers' agreement, ensures the package builds and tests successfully, and confirms it's compatible with the newest versions of its dependencies. Submissions happen via pull requests, which get automatically checked for compatibility. Everyday users who just want to use Stackage don't need this repo, they go to stackage.org or use a build tool called Stack that has Stackage built in. The broader project spans several repositories: one for the server that hosts stackage.org, one for the curator tooling, and others for the nightly and LTS package sets themselves. There's also a data flow document for anyone curious about how the pieces connect. Building the entire package set yourself is possible but not recommended, the maintainers note that you'll likely run into issues you have to debug on your own.