Over the last year, Well-Typed have carried out significant work in Cabal, Haskell’s build system, thanks to funding from the Sovereign Tech Fund. Our main goal was to re-think the Cabal architecture for building packages. This was historically tied to the Setup command-line interface, with each package technically capable of providing its own independent build system via the Custom build-type. In practice, the full generality of this interface is not useful, and it obstructs the development of new features and created a drag on maintenance, so there has long been an appetite to reimagine this interface within Cabal.¹

With the release of Cabal-3.14.0.0 and cabal-install-3.14.1.1, the new Hooks build-type we have developed, together with the Cabal-hooks library, are now available to package authors. Over time, we hope to see packages that depend on the Custom build-type gradually migrate to use Hooks instead.

For more background on this work, check out:

• our blog post introducing the project,

• our HF Tech Proposal in which the design was discussed with the developer community, and

• the Distribution.Simple.SetupHooks documentation.

In the remainder of this post, we will:

• dive into the background details of how Cabal works,

• provide an introduction to the new interfaces for package authors who may wish to adapt their packages.

This post is based on Sam’s talk at the Haskell Ecosystem Workshop 2024.

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