code_coverage.yml

# Contains jobs corresponding to code coverage.

name: Code Coverage

# Controls when the action will run. Triggers the workflow on pull request
# events or push events in the develop branch.
on:
  workflow_dispatch:
  pull_request:
  push:
    branches:
      # Push events on develop branch
      - develop

jobs:
  compute_changed_files:
    name: Compute changed files
    runs-on: ubuntu-20.04
    outputs:
      matrix: ${{ steps.compute-file-matrix.outputs.matrix }}
      can_skip_tests: ${{ steps.compute-file-matrix.outputs.can_skip_files }}
    env:
      CACHE_DIRECTORY: ~/.bazel_cache
    steps:
      - uses: actions/checkout@v2
        with:
          fetch-depth: 0

      - name: Set up Bazel
        uses: abhinavsingh/setup-bazel@v3
        with:
          version: 6.5.0

      - uses: actions/cache@v2
        id: scripts_cache
        with:
          path: ${{ env.CACHE_DIRECTORY }}
          key: ${{ runner.os }}-${{ env.CACHE_DIRECTORY }}-bazel-scripts-${{ github.sha }}
          restore-keys: |
            ${{ runner.os }}-${{ env.CACHE_DIRECTORY }}-bazel-scripts-
            ${{ runner.os }}-${{ env.CACHE_DIRECTORY }}-bazel-

      # This check is needed to ensure that Bazel's unbounded cache growth doesn't result in a
      # situation where the cache never updates (e.g. due to exceeding GitHub's cache size limit)
      # thereby only ever using the last successful cache version. This solution will result in a
      # few slower CI actions around the time cache is detected to be too large, but it should
      # incrementally improve thereafter.
      - name: Ensure cache size
        env:
          BAZEL_CACHE_DIR: ${{ env.CACHE_DIRECTORY }}
        run: |
          # See https://stackoverflow.com/a/27485157 for reference.
          EXPANDED_BAZEL_CACHE_PATH="${BAZEL_CACHE_DIR/#\~/$HOME}"
          CACHE_SIZE_MB=$(du -smc $EXPANDED_BAZEL_CACHE_PATH | grep total | cut -f1)
          echo "Total size of Bazel cache (rounded up to MBs): $CACHE_SIZE_MB"
          # Use a 4.5GB threshold since actions/cache compresses the results, and Bazel caches seem
          # to only increase by a few hundred megabytes across changes for unrelated branches. This
          # is also a reasonable upper-bound (local tests as of 2021-03-31 suggest that a full build
          # of the codebase (e.g. //...) from scratch only requires a ~2.1GB uncompressed/~900MB
          # compressed cache).
          if [[ "$CACHE_SIZE_MB" -gt 4500 ]]; then
            echo "Cache exceeds cut-off; resetting it (will result in a slow build)"
            rm -rf $EXPANDED_BAZEL_CACHE_PATH
          fi

      - name: Configure Bazel to use a local cache
        env:
          BAZEL_CACHE_DIR: ${{ env.CACHE_DIRECTORY }}
        run: |
          EXPANDED_BAZEL_CACHE_PATH="${BAZEL_CACHE_DIR/#\~/$HOME}"
          echo "Using $EXPANDED_BAZEL_CACHE_PATH as Bazel's cache path"
          echo "build --disk_cache=$EXPANDED_BAZEL_CACHE_PATH" >> $HOME/.bazelrc
        shell: bash

      - name: Compute file matrix
        id: compute-file-matrix
        env:
          compute_all_files: ${{ contains(github.event.pull_request.title, '[RunAllTests]') }}
          # See: https://docs.github.com/en/webhooks-and-events/webhooks/webhook-events-and-payloads#pull_request. Defer to origin/develop outside a PR (such as develop's main CI runs).
          base_commit_hash: ${{ github.event.pull_request.base.sha || 'origin/develop' }}
        # https://unix.stackexchange.com/a/338124 for reference on creating a JSON-friendly
        # comma-separated list of test targets for the matrix.
        run: |
          bazel run //scripts:compute_changed_files -- $(pwd) $(pwd)/changed_files.log $base_commit_hash compute_all_files=$compute_all_files
          FILE_BUCKET_LIST=$(cat ./changed_files.log | sed 's/^\|$/"/g' | paste -sd, -)
          echo "Changed files (note that this might be all files if configured to run all or on the develop branch): $FILE_BUCKET_LIST"
          echo "::set-output name=matrix::{\"changed-files-bucket-base64-encoded-shard\":[$FILE_BUCKET_LIST]}"
          if [[ ! -z "$FILE_BUCKET_LIST" ]]; then
            echo "::set-output name=can_skip_files::false"
          else
            echo "::set-output name=can_skip_files::true"
            echo "No files are affected by this change. If this is wrong, you can add '[RunAllTests]' to the PR title to force a run."
          fi