stack-ci.yml

# Copyright 2021 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

name: Stack CI

on:
  push:
    branches:
      - main
  pull_request:
    types:
      - opened
      - reopened
      - synchronize

# Cancel earlier runs for pushes to the same branch or updates to the same PR.
concurrency:
  group: ci-${{ github.ref }}
  cancel-in-progress: true

jobs:
  prepare:
    name: Determine Build Matrix
    runs-on: ubuntu-latest
    timeout-minutes: 2

    outputs:
      ci-builds: ${{ steps.read-builds.outputs.ci-builds }}

    steps:
      - name: Checkout
        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f

      - name: Read matrix.yaml
        id: read-builds
        run: |
          cat matrix.yaml
          CI_BUILDS=$(yq eval -o json -I 0 matrix.yaml)
          echo "::set-output name=ci-builds::$CI_BUILDS"

  build:
    name: Build and Test
    runs-on: ubuntu-latest
    needs: prepare
    timeout-minutes: 30

    strategy:
      fail-fast: false
      matrix: ${{ fromJson(needs.prepare.outputs.ci-builds) }}

    env:
      STACK: "stack --lock-file read-write --resolver ${{ matrix.build.resolver }} --compiler ${{ matrix.build.compiler }}"

      ghc-cache-ver: v1
      dep-cache-ver: v1
      mod-cache-ver: v1

    steps:
      - name: Checkout
        uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f

      # Install Stack without GHC first, so we have an opportunity to cache the
      # Pantry package index.
      - name: Install Stack
        uses: haskell/actions/setup@eb3073b623d53d0cdd38e4d4c2408f14e3fc71c5
        id: setup-stack
        with:
          enable-stack: true
          stack-no-global: true

      # The cache key for the Pantry package index.
      - name: Fetch Hackage Stamp
        run: curl -O https://hackage.haskell.org/timestamp.json

      # Try to avoid rebuilding the whole Pantry index, since it takes over a
      # minute to parse and index all the Cabal files on Hackage from scratch.
      #
      # Pantry will try to incrementally extend its index if it gets an
      # out-of-date one, so we benefit from using restore-keys to bootstrap it
      # with a previous index.
      - name: Cache Pantry Package Index
        uses: actions/cache@c64c572235d810460d0d6876e9c705ad5002b353
        with:
          # Everything except the decompressed Hackage index tarball.  Why is
          # that even materialized to disk?
          path: |
            ${{ steps.setup-stack.outputs.stack-root }}/pantry/pantry*
            ${{ steps.setup-stack.outputs.stack-root }}/pantry/hackage/*
            !${{ steps.setup-stack.outputs.stack-root }}/pantry/hackage/*.tar.gz
          key: ${{ runner.os }}-${{ matrix.build.compiler }}-${{ hashFiles('timestamp.json') }}
          restore-keys: |
            ${{ runner.os }}-${{ matrix.build.compiler }}-
            ${{ runner.os }}-

      # GHC takes a while to gunzip and configure; let's try caching it
      # pre-configured with zstd.
      - name: Cache Configured GHC
        uses: actions/cache@c64c572235d810460d0d6876e9c705ad5002b353
        with:
          # Omit the tarball itself; it'll double the cache size assuming
          # similar compression ratios.
          path: |
            ${{ steps.setup-stack.outputs.stack-root }}/programs/*/*
            !${{ steps.setup-stack.outputs.stack-root }}/programs/*/*.tar.xz
          key: ${{ env.ghc-cache-ver}}-${{ runner.os }}-${{ matrix.build.compiler }}

      # Explicitly fetch the Hackage index to make sure we notice any metadata
      # revisions.  Do this /before/ stack setup, since that's when Stack locks
      # down its choices to a particular cabal file sha256sum in its lockfile.
      - name: Update Hackage Index
        run: $STACK update

      # Now do stack setup, which should do as little cabal-file-indexing work
      # as possible.
      - name: Pre-install GHC with Stack
        run: $STACK setup

      # Have stack construct a build plan and lock file for use as a cache key.
      - name: Determine Build Plan
        run: |
          $STACK build --test --dry-run
          echo '\n' stack.yaml.lock ${{ hashFiles('stack.yaml.lock') }}

      # Cache pre-built dependencies from the same lock file; restore from
      # other builds with the same GHC version to benefit from any packages in
      # common between two lockfiles.
      - name: Cache Dependencies
        uses: actions/cache@c64c572235d810460d0d6876e9c705ad5002b353
        with:
          # The Stack global work directory, minus GHC installations (already
          # extracted from a tarball) and the Pantry package index (already
          # cached).
          #
          # Excluding subdirectories of an included directory doesn't work, so
          # glob everything inside $STACK_ROOT and then exclude the
          # subdirectories we don't want.
          path: |
            ${{ steps.setup-stack.outputs.stack-root }}/*
            !${{ steps.setup-stack.outputs.stack-root }}/programs
            !${{ steps.setup-stack.outputs.stack-root }}/pantry
          key: ${{ env.dep-cache-ver }}-${{ runner.os }}-${{ matrix.build.compiler }}-${{ hashFiles('stack.yaml.lock') }}
          restore-keys: |
            ${{ env.dep-cache-ver }}-${{ runner.os }}-${{ matrix.build.compiler }}-

      # We just overwrote some Stack internal files with a cached version that
      # has an older timestamp for the GHC binary, which will confuse it on the
      # next command.  Quarantine the warnings in their own step for
      # aesthetics, even though they wouldn't be harmful if we just let them
      # happen in the next build step.
      - name: Refresh GHC Metadata
        run: |
          echo "Re-running setup to let Stack update GHC's timestamp."
          echo "A warning about mismatched GHC metadata is expected."
          echo
          $STACK setup

      # Build the dependencies, hopefully doing little to no work.
      - name: Build Dependencies
        run: $STACK build --test --only-dependencies

      # Cache pre-built modules for incremental builds, making sure to keep
      # builds with different dependencies separate.
      - name: Cache Modules
        uses: actions/cache@c64c572235d810460d0d6876e9c705ad5002b353
        with:
          path: "**/.stack-work"
          key: |
            ${{ env.mod-cache-ver }}-${{ runner.os }}-${{ matrix.build.compiler }}-${{ hashFiles('stack.yaml.lock') }}-${{hashFiles('**/*.hs', '**/package.yaml') }}
          restore-keys: |
            ${{ env.mod-cache-ver }}-${{ runner.os }}-${{ matrix.build.compiler }}-${{ hashFiles('stack.yaml.lock') }}-
            ${{ env.mod-cache-ver }}-${{ runner.os }}-${{ matrix.build.compiler }}-

      # Build, Haddock, and test, taking care to build in only one
      # configuration to make caching work as well as possible.  In practice,
      # this means building modules, tests, and documentation all at once, then
      # running tests under the same configuration afterwards.  Separating them
      # isn't crucial; it's just to make the CI results easier to understand.
      #
      # Using --no-haddock-deps somehow forces it to rebuild from scratch every
      # time, so leave that out -- rebuilding unconditionally seems worse than
      # building (and caching) dependencies' haddock.
      - name: Build
        run: $STACK build --test --no-run-tests

      # Run tests with concurrency disabled; see
      # https://github.com/commercialhaskell/stack/issues/5024.
      - name: Test
        run: $STACK build --test -j 1

      - name: Haddock
        run: $STACK build --haddock --test --no-run-tests