cache-generator.yml

# This workflow is the single source of truth for generating and updating various caches used by our CI pipeline.
# It sets the fresh cache each Monday but provides a manual trigger to update it on-demand.
#
# All other jobs only restore from this cache; *they never update it*!
# They should always use `actions/cache/restore@v4` because `actions/cache@v4` would attempt to save the cache.
#
# Our agreed-upon strategy is to use a deterministic cache key based on the week of the year.
# Jobs can utilize the prior week's cache if the current week's cache is not found.
#
#
# PRINCIPLES:
#   - The cache is never wrong!
#   - Caches are immutable once created.
#   - Caches are for speeding up builds, not for correctness.
#   - It is faster to download a large cache than to re-resolve missing dependencies.
#
#
# DESIGN:
#
# 1. Prepare
#     - A job first prepares the local environment (e.g., installs JDK, Clojure, Node.js, etc.)
#     - This fetches the dependencies from the cache (if it exists) and warms up the local cache for this workflow.
# 2. Resolve
#     - The next step pre-resolves all dependencies, ensuring that the local cache is fully populated and up-to-date.
# 3. Update
#     - The final step saves the local cache back to GitHub Actions cache with a deterministic key.
#     - If a cache entry already exists for that key, it is deleted first to ensure immutability.
#
name: Cache Generator

on:
  schedule:
    - cron: "0 3 * * 1" # Mondays at 03:00 UTC
  workflow_dispatch: # manually update the cache

concurrency:
  group: cache-generator
  cancel-in-progress: true

jobs:
  get-cache-keys:
    runs-on: ubuntu-22.04
    steps:
      - uses: actions/checkout@v4
      - name: Get cache keys
        uses: ./.github/actions/get-cache-keys
        id: get-cache-keys
    outputs:
      m2-cache-key: ${{ steps.get-cache-keys.outputs.m2-cache-key }}
      node-cache-key: ${{ steps.get-cache-keys.outputs.node-cache-key }}
      eslint-cache-key: ${{ steps.get-cache-keys.outputs.eslint-cache-key }}
      cypress-cache-key: ${{ steps.get-cache-keys.outputs.cypress-cache-key }}

  generate-caches:
    runs-on: ubuntu-22.04
    timeout-minutes: 30
    needs: get-cache-keys
    env:
      M2_CACHE_KEY: ${{ needs.get-cache-keys.outputs.m2-cache-key }}
      NODE_CACHE_KEY: ${{ needs.get-cache-keys.outputs.node-cache-key }}
      CYPRESS_CACHE_KEY: ${{ needs.get-cache-keys.outputs.cypress-cache-key }}
      ESLINT_CACHE_KEY: ${{ needs.get-cache-keys.outputs.eslint-cache-key }}
    steps:
      - uses: actions/checkout@v4

      # Backend preparation and cache
      - name: Prepare backend
        uses: ./.github/actions/prepare-backend

      # Add or remove aliases to affect the cache size and its contents.
      # Adjust to taste, then redeploy this workflow.
      - name: Pre-resolve Clojure dependencies
        run: clojure -A:build:dev:ee:ee-dev:drivers:drivers-dev:cljs -P

      - name: Update M2 cache
        uses: ./.github/actions/update-cache
        with:
          path: |
            ~/.m2
            ~/.gitlibs
          key: ${{ env.M2_CACHE_KEY }}

      # Frontend preparation and caches
      # `prepare-frontend` action (1) prepares Node.js and (2) fetches the node_modules cache if it exists.
      # It then (3) runs `yarn install --frozen-lockfile --prefer-offline` which ensures the local cache is fully populated.
      # IMPORTANT: Caching node_modules after patches are already applied will break any PR that attempts to either:
      #   - upgrade a patched library
      #   - change a patch
      # Hence why we explicitly exclude patches from the cache (controlled by the `apply-patches` action input).
      - name: Install front-end dependencies
        uses: ./.github/actions/prepare-frontend
        with:
          apply-patches: "false"

      - name: Get yarn cache directory
        id: yarn-cache-dir
        run: |
          YARN_CACHE_DIR=$(yarn cache dir)
          echo "Yarn cache directory: $YARN_CACHE_DIR"
          echo "dir=$YARN_CACHE_DIR" >> $GITHUB_OUTPUT

      - name: Ensure that Cypress executable is ready
        run: |
          yarn cypress install
          yarn cypress cache path
          yarn cypress cache list
          yarn cypress verify
        shell: bash

      # Run Prettier to populate its cache (stored in node_modules/.cache/prettier)
      # so it gets saved as part of the node_modules cache below
      - name: Run Prettier to populate cache
        run: yarn lint-prettier-pure

      - name: Update node_modules cache
        uses: ./.github/actions/update-cache
        with:
          path: |
            ${{ steps.yarn-cache-dir.outputs.dir }}
            node_modules
          key: ${{ env.NODE_CACHE_KEY }}

      - name: Update Cypress cache
        uses: ./.github/actions/update-cache
        with:
          path: ~/.cache/Cypress
          key: ${{ env.CYPRESS_CACHE_KEY }}

      # ESLint cache (requires both backend and frontend)
      - name: Compile CLJS
        run: yarn build-pure:cljs

      - name: Run ESLint to populate cache
        run: yarn lint-eslint-pure

      - name: Update eslint cache
        uses: ./.github/actions/update-cache
        with:
          path: ${{ github.workspace}}/.eslintcache
          key: ${{ env.ESLINT_CACHE_KEY }}