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This project is built around the concept of maintainers taking responsibility for making their packages work with the rest of the stable ecosystem, usually meaning the newest version of all dependencies. This is a social contract, and is not reflected in the codebase in any way.

The idea behind Stackage is that, if all packages work with the newest versions of dependencies, we avoid dependency hell. Specifically, we aim for:

Packages in Stackage are not patched: all package changes occur upstream in Hackage.

Adding a package

Anyone can add any package to Stackage but you should talk to the upstream maintainer before putting another person's package under your own name. It's generally better the actual package maintainer is also the Stackage maintainer, if that is not the case you should write the package maintainer a note first, eg by opening an upstream issue or sending them an email.

To add your package you can edit build-constraints.yaml directly on github or fork the project. There's a section called packages where you would add yourself and your packages:

"My Name <> @mygithubuser":
    - package1
    - package2
    - package3

(If you are adding yourself for the first time, you can add yourself anywhere under the packages: section, it does not have to be at the end: this actually helps to avoid merge conflicts between new contributions.)

Any dependencies of your packages that are not already part of stackage also need to be added explicitly (When this happens you will see not present errors in the CI log). As mentioned above: If you don't maintain this package yourself it is preferable that the actual maintainer is also the stackage maintainer, but you are allowed to add it under your own name.

If your package depends on a C library, please add it to docker/ or docker/

After doing that, commit with a message like "add foo-bar" and send a pull request.

The continuous integration job will do some checks to see if your package's dependencies are up-to-date.

The CI job notably doesn't compile packages, run tests, build documentation, or find missing C libraries. If you want to be proactive or if CI fails, you can make sure that your package builds against the latest nightly. See the verify-package script in this repository.

This approach works well, but has two limitations you should be aware of:

  • It won't notify you of restrictive upper bounds in your package if Stackage has the same upper bounds. For that reason, we recommend using Packdeps (see "Following dependency upgrades" below). You can also run cabal outdated.
  • If the latest Stackage Nightly is missing some of the latest packages, your build above may succeed whereas the Travis job may fail. Again: Packdeps will help you detect this situation.

Github and Notifications

Stackage uses Github notifications to reduce overhead of contacting individual package maintainers through various channels. As a package maintainer, you will receive notifications for a number of reasons, package build failures of different sorts, blockages and bounds issues, etc.

Please note, Github does some throttling on the number people that can be notified within one issue. This means that on issues created with a large number of packages affected, maintainers may not receive a notification. This is not ideal, but Stackage is largely a manual process and done on a best effort basis.

Uploading a new package version

When a new version of a package in Stackage is uploaded to Hackage, we automatically try to include it in Stackage. That can result in a number of possible failures. If there is a failure we temporarily introduce an upper bound, and open a GitHub issue ticket to resolve the issue.

If the new version doesn't compile then the package author should upload a fixed version.

If a package's test suite is failing, the first job is to investigate why. If this is due to a bad interaction with versions of other packages in Stackage, then it is the responsibility of the maintainer to fix the test suite. In some situations, it is acceptable to not run the test suite.

Moving or retiring maintainership of a Stackage package

If you no longer wish to be listed as maintainer of a package in Stackage, you can open a pull request to move it to a new maintainer or to either the "Grandfathered dependencies" or the "Abandoned packages" sections in build-constraints.yaml. Unless there is a compelling technical reason to remove the package, this is better than just dropping it from the distribution.

Following dependency upgrades

If a new version of a dependency is released your package may fail to build or tests may fail. In most cases we will add an upper bound on the dependency so that your package remains in nightly. We'll also create a github issue pinging you with the bounds issues or give build logs showing failures. It's then up to you to modify your package.

We recommend that you also follow the dependencies of your packages on Packdeps (typically using the RSS feeds) as well as that often gives you notice ahead of stackage issues. There are cases where we will not notice a new release of a package because of other upper bounds that are in place.

If a package is not updated in time, it may be temporarily removed from Stackage by the curator team. We strive to notify you when this happens. If it does you are always welcome to file another pull request to add it back.

We typically use fairly long windows before disabling packages, but it is decided on a case-by-case basis.

  • If restrictive version bounds are the only problem, we will give maintainers at least a week to respond.
  • If there are real breaking changes, the curator team will retain more discretion on how long a window to give before dropping packages.
  • We typically drop upper bounds and disable conflicting packages in Nightly after we create a new Long Term Support (LTS) major version.
  • There are rare cases where an upper bound or build failure are hard to deal with so then we may disable

NOTE Previously we had stricter time limits, but we decided to remove that: Anyone is free to add a package to Stackage regardless of responsiveness guarantees. However, as stated above, we may elect to temporarily remove a package if it is not updated in a timely manner.

Understanding stackage issues

Bounds issues

These are the most common.

Using #6217 as an example.

Our convention is to title a PR after the package that is being held back from the nightly snapshot (here: aeson).

The issue body is templated and looks like this:

aeson- ([changelog]( (MAINTAINER) is out of bounds for:
- [ ] Agda-2.6.2 (>= && < 1.6). MAINTAINER. Used by: library
- [ ] HsYAML-aeson- (>= && < 1.6). MAINTAINER. Used by: library
- [ ] IPv6Addr-2.0.2 (>= && < 1.6). MAINTAINER. Used by: library

This (usually - see "Other issues") means that there was a new release of the package in the header (aeson). This is expected and the aeson maintainer is not expected to act. They are pinged to notify them that the latest version of their package will not be part of the nightly snapshots until the issue closed.

The list of packages with checkboxes denote the packages that prevent us from using the latest version of aeson, the first version number is the current version of that package in nightly (e.g. Agda 2.6.2). The constraint in parenthesis (>= && < 1.6) is Agda's current bound on aeson. To check this box we expect there to be an update of Agda to support aeson

Once all boxes are checked we should be able to close the issue and upgrade aeson.

Other issues

Other common types of issues are

  • Packages with failing tests, haddocks, or benchmarks (note that we only compile benchmarks)
    • Maintainers may choose to update these parts of their package, or to exclude them from the stackage build (e.g. adding a package to skipped-tests)
  • New releases of packages that depend on packages that are not a part of stackage. This is denoted as not present
    • Maintainers are encouraged to ask the maintainer of these packages to join stackage, or to be the stackage contact person themselves.
  • A new release of a package with stricter upper bounds than its previous version
    • This will look like a normal bounds issue, and should be treated the same way by maintainers. Curators usually resolve this by adding an upper bound to that package instead of its dependency.


Maintainers are humans, humans get sick/have babies/go on holiday. Sometimes a dependency upgrade is extra time consuming.

Consider finding a co-maintainer with access to SCM and Hackage to help you out.

We appreciate if you notify us of any expected delays in the Github issues, some kind soul might decide to help out.

Upgrading to a new GHC version

The Stackage curation team tries to move Stackage Nightly to new versions of GHC quickly as they become available, while keeping LTS Haskell on a regular release schedule. For package maintainers, the most important impacts of a new GHC release are:

  • We will typically do a sweep through the Stackage upper bounds and remove blocking packages. We prefer to do it this way rather than ask other maintainers to backport fixes.
    • We will definitely do this at a GHC major version release, and may do so at a minor version release
  • Packages that are incompatible with the newest GHC version will be temporarily disabled

If your package ends up being temporarily disabled from Stackage Nightly, please simply send a pull request to add it back once it and its dependencies are compatible with the newest GHC version.

Note that it is not a goal of LTS Haskell to track the latest version of GHC. If you want the latest and greatest, Stackage Nightly is your best bet. In particular, LTS Haskell will often—but not always—avoid upgrading to the first point release of GHC releases (e.g., 8.x.1) to allow further testing and to get the benefits of the first bugfix release (e.g., 8.x.2).

Adding a package to an LTS snapshot

The steps above affect the Stackage Nightly builds, but do not directly affect LTS Haskell builds. When we build a new LTS Haskell major version (anything ending in .0), the package set is taken from Stackage Nightly. Therefore, by following the above steps, you can get your package into the next major LTS Haskell release.

If you would like to get your package added to the current LTS Haskell major release, please do the following in addition to the steps for Nightly described earlier:

  • Check that your package can be built with the current LTS version (e.g. stack build --test --bench --haddock --resolver lts)
  • Fork lts-haskell repo if you haven't already
  • Open up a pull request on the lts-haskell repo for the appropriate build-constraints/lts-*-build-constraints.yaml
  • Be patient! The LTS releases are less frequent than Nightly. The Stackage curators will try to get to your issue as soon as possible, but it may take some time.

LTS package guarantees and exceptions

In general, we try to stick to some rules when it comes to the packages included in LTS minor bumps. In particular:

  • If a package exists in LTS-X.Y, it should also exist in LTS-X.(Y+1)
  • We should not include a major version bump of a package between LTS-X.Y and LTS-X.(Y+1)

However, there are some cases where exceptions may be made, based purely on Stackage Curator discretion. The most common examples are:

  • If a package does not follow the PVP in its version number policy, applying the standard version bump rules would not necessarily makes sense. As an example, suppose package foo decides to follow SemVer instead of the PVP. By our standard rules of version bumps, a change from foo-1.2.0 to foo-1.3.0 would be considered a major version bump, and disallowed in an LTS minor version bump. However, if a package is following SemVer, this would not be a breaking change, and curators may elect to include it. Note though that curators and their tooling will not know your package is following SemVer, so in this case you would have to open an issue on the lts-haskell repo.

  • If a package has overly restrictive version bounds on a dependency, in particular constraining a minor version unnecessarily, we may drop that package instead of artificially holding back the dependency. As an example: suppose LTS-20.1 includes foo-1.2.0 and bar-1. bar-1 has a dependency foo >= 1.2.0 && < 1.2.1, which is overly constrained on the minor version number according to the PVP. Then foo-1.2.1 is released. The Stackage Curator team would have two choices:

    • Reject foo-1.2.1 from LTS-20.2, since that is what bar-1 requires.
    • Drop bar-1 from LTS-20.2, and allow foo-1.2.1.

    Decisions will need to be taken on a case-by-case basis, and may depend on such issues as whether an important bugfix or security update in included. The curator team may also try to notify the author of bar to try and get a patched version released.