cabal-cache-native

This action caches the build dependencies of a Haskell project with per-package granularity. It works out of the box and it is really fast.

Usage

When building a Haskell project with cabal, cabal caches the project dependencies in a global cache called the "store". These are identified by a key that accurately represents their build configuration so they can be shared between projects.

Using @actions/cache to cache the entire store is not optimal because it would either cache the entirety of the store or nothing at all; which cabal does already at keeping track of what can be shared between builds and what can't.

The complexity of the example workflow from haskell-actions/setup is a testament to this issue.

Features

• Automatic: the action detects the project's dependencies directly from cabal's build plan and caches them automatically.
• Fast: the cache is stored in GitHub's own cache and it is restored very quickly.
• Accurate: the cached packages are identified by the same package-hash used by cabal, allowing GitHub to garbage-collect them individually when they are not needed anymore.

Usage

To use this action you need to get cabal to create a build plan (i.e. the plan.json file). This is typically achieved by passing the --dry-run flag to the build command. Once plan.json has been created, cabal-cache-native will read from it the ids of the units to restore from cache. The action will look for plan.json in ${project-path}/${plan-json}.

jobs:
  build:
    steps:
      - uses: haskell-actions/setup
        id: setup

      # ...

      # This step is required to generate the build plan
      - run: cabal build all --dry-run

      - uses: andreabedini/cabal-cache-native
        with:
          # required
          store-path: ${{ steps.setup.outputs.cabal-store }}

          # optional, the path to the project
          # project-path: .

          # optional, you can also specify the exact location of plan.json
          # plan-json: dist-newstyle/cache/plan.json

          # optional, use this to separate caches or to start from scratch.
          # cache-key-prefix: cabal

          # optional, use this ghc to locate ghc-pkg
          # ghc: ghc

          # optional, use this ghc-pkg
          # ghc-pkg: ghc-pkg

      # No need to check for cache hits, just build your project!
      - run: cabal build all

NOTE: cabal build has to be the same command you use to build (plus --dry-run) otherwise you risk caching the wrong dependencies. This should not cause build failures, but it will cause unnecessary recompilations.

License

You are welcome to use this under the MIT license included in the repository.