main.yml

# SPDX-License-Identifier: BSD-2-Clause

name: Continuous Integration

on:
  push:
    branches:
      - main
  pull_request:
    branches:
      - main

env:
  # Always use the Xvfb service's display.
  DISPLAY: ":99"

jobs:
  bazel_test:
    runs-on: ubuntu-latest
    env:
      # This is where bazelisk caches its downloads of Bazel.
      BAZELISK_HOME: /home/runner/.cache/bazel_ci/bazelisk
    steps:
      - uses: actions/checkout@v4
      - name: Install Ubuntu dependencies
        run: .github/ci_setup.bash
      # Restore the most appropriate caches.
      #
      # In the below: `github.ref` will be either "refs/pull/<pr_number>/merge"
      # or "refs/heads/main"; `github.run_number` is a monotonically increasing
      # serial number; and `github.run_attempt` is a typically 1.
      #
      # The `key` declared here will never match (since it encodes the current
      # run_number) but illustrates the name we'll use to save the caches when
      # we're done.
      #
      # However, one of the `restore-keys` patterns *should* always match. The
      # effects we should see from the `restore-keys` patterns are:
      #
      # * When building the `main` branch, we'll always pull the most recently
      #   updated main caches. Both restore keys say "pip-refs/heads/main-" and
      #   the prior archives are named, e.g., "pip-refs/heads/main-####-#".
      #   GitHub will use the *most recently saved* archive name that matches
      #   the restore key prefix (no matter the lexicographic ordering of
      #   the ####-# part).
      #
      # * Ditto for the first build of a PR; the first restore key will not
      #   match anything, so it falls back to the main caches.
      #
      # * For subsequent builds of a PR, the first restore key, e.g.,
      #   "pip-refs/pull/###/merge-" should match the most recently saved PR key
      #   "pip-refs/pull/###/merge-####-#".
      - uses: actions/cache/restore@v4
        with:
          path: ~/.cache/pip
          # N.B. The "-mumble" suffix below will never match; it's a placeholder
          # for the nonce appended to the cache key. Instead, the restore-keys
          # will always be used for restoring.
          key: pip-${{ github.ref }}-${{ github.run_number }}-${{ github.run_attempt }}
          restore-keys: |
            pip-${{ github.ref }}-
            pip-refs/heads/main-
      - uses: actions/cache/restore@v4
        with:
          path: ~/.cache/bazel_ci
          key: bazel_ci-${{ github.ref }}-${{ github.run_number }}-${{ github.run_attempt }}
          restore-keys: |
            bazel_ci-${{ github.ref }}-
            bazel_ci-refs/heads/main-
      - name: Report cache sizes
        run: |
          du -ms ~/.cache/pip || true
          du -ms ~/.cache/bazel_ci/* || true
      # Actual testing.
      - name: Bazel Test
        run: |
          ln -s .github/ci.bazelrc user.bazelrc
          ./bazel test //...
      # Save the updated cache snapshots, so we never do the same work twice.
      # By default, actions/cache only saves after a successful workflow, but
      # our caches are bags of files where we only ever add new files (not change
      # an existing files), so it's always safe to snapshot.
      - uses: actions/cache/save@v4
        if: always()
        with:
          path: ~/.cache/pip
          key: pip-${{ github.ref }}-${{ github.run_number }}-${{ github.run_attempt }}
      - uses: actions/cache/save@v4
        if: always()
        with:
          path: ~/.cache/bazel_ci
          key: bazel_ci-${{ github.ref }}-${{ github.run_number }}-${{ github.run_attempt }}