build-impact.yml

# Copyright (c) Facebook, Inc. and its affiliates.
#
# 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: Build Impact Analysis

on:
  push:
    branches:
      - main
    paths:
      - velox/**
      - CMakeLists.txt
      - CMake/**
      - .github/workflows/build-impact.yml
      - .github/scripts/generate-dependency-graph.py
      - .github/scripts/detect-build-impact.py

  pull_request:
    paths:
      - velox/**
      - '!velox/docs/**'
      - CMakeLists.txt
      - CMake/**
      # TODO: Remove after testing comment workflow
      - .github/**

permissions:
  contents: read
  actions: read

concurrency:
  group: ${{ github.workflow }}-${{ github.repository }}-${{ github.head_ref || github.sha }}
  cancel-in-progress: true

jobs:
  # ==========================================================================
  # Push to main: generate and upload the dependency graph artifact.
  # ==========================================================================
  generate-graph:
    if: github.event_name == 'push'
    runs-on: 8-core-ubuntu
    container: ghcr.io/facebookincubator/velox-dev:adapters
    env:
      VELOX_DEPENDENCY_SOURCE: SYSTEM
    steps:
      - uses: actions/checkout@v5
        with:
          persist-credentials: false

      - uses: ./.github/actions/generate-dependency-graph

      - name: Upload dependency graph
        uses: actions/upload-artifact@v4
        with:
          name: dependency-graph
          path: dependency-graph.json
          retention-days: 90

  # ==========================================================================
  # Pull request: check what changed and whether the graph artifact exists.
  # ==========================================================================
  check-changes:
    if: github.event_name == 'pull_request'
    runs-on: ubuntu-latest
    outputs:
      cmake-changed: ${{ steps.check.outputs.cmake_changed }}
      graph-available: ${{ steps.artifact.outputs.available }}
      graph-run-id: ${{ steps.artifact.outputs.run_id }}
      use-slow-path: ${{ steps.decide.outputs.slow }}
    steps:
      - name: Get changed files
        id: check
        env:
          GH_TOKEN: ${{ github.token }}
        run: |
          # Use the GitHub API to get the changed files directly.
          # This avoids issues with fork PRs where HEAD_SHA may not
          # be available in the local clone.
          gh api --paginate \
            "/repos/${{ github.repository }}/pulls/${{ github.event.pull_request.number }}/files" \
            -q '.[].filename' > changed_files.txt
          cat changed_files.txt

          # Check if any CMake files changed.
          if grep -qE '(CMakeLists\.txt|CMake/.+\.cmake)$' changed_files.txt; then
            echo "cmake_changed=true" >> "$GITHUB_OUTPUT"
            echo "CMake files changed — slow path needed."
          else
            echo "cmake_changed=false" >> "$GITHUB_OUTPUT"
          fi

      - name: Check if graph artifact exists
        id: artifact
        env:
          GH_TOKEN: ${{ github.token }}
        run: |
          # Find the latest successful generate-graph run on main.
          run_id=$(gh api \
            "/repos/${{ github.repository }}/actions/workflows/build-impact.yml/runs?branch=main&status=success&per_page=5" \
            -q '.workflow_runs[0].id // empty')

          if [ -z "$run_id" ]; then
            echo "available=false" >> "$GITHUB_OUTPUT"
            echo "No graph artifact found — slow path needed."
          else
            echo "available=true" >> "$GITHUB_OUTPUT"
            echo "run_id=$run_id" >> "$GITHUB_OUTPUT"
            echo "Graph artifact available from run $run_id."
          fi

      - name: Decide fast or slow path
        id: decide
        env:
          CMAKE_CHANGED: ${{ steps.check.outputs.cmake_changed }}
          GRAPH_AVAILABLE: ${{ steps.artifact.outputs.available }}
        run: |
          if [[ "$CMAKE_CHANGED" == "true" ]] || \
             [[ "$GRAPH_AVAILABLE" == "false" ]]; then
            echo "slow=true" >> "$GITHUB_OUTPUT"
          else
            echo "slow=false" >> "$GITHUB_OUTPUT"
          fi

      - name: Upload changed files list
        uses: actions/upload-artifact@v4
        with:
          name: changed-files
          path: changed_files.txt

  # ==========================================================================
  # Fast path: download pre-computed graph, run impact detection.
  # ==========================================================================
  fast-detect:
    needs: check-changes
    if: needs.check-changes.outputs.use-slow-path == 'false'
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v5
        with:
          persist-credentials: false

      - name: Download changed files
        uses: actions/download-artifact@v4
        with:
          name: changed-files

      - name: Download dependency graph
        uses: actions/download-artifact@v4
        with:
          name: dependency-graph
          github-token: ${{ github.token }}
          repository: ${{ github.repository }}
          run-id: ${{ needs.check-changes.outputs.graph-run-id }}

      - name: Run impact detection
        run: |
          python3 .github/scripts/detect-build-impact.py \
            --graph dependency-graph.json \
            --changed-files changed_files.txt \
            --build-type release \
            --graph-source "Fast path • Graph from main@${{ github.event.pull_request.base.sha }}" \
            --output comment.md

      - name: Upload comment
        uses: actions/upload-artifact@v4
        with:
          name: build-impact-comment
          path: comment.md

  # ==========================================================================
  # Slow path: generate graph from PR branch, then run impact detection.
  # ==========================================================================
  slow-detect:
    needs: check-changes
    if: needs.check-changes.outputs.use-slow-path == 'true'
    runs-on: 8-core-ubuntu
    container: ghcr.io/facebookincubator/velox-dev:adapters
    env:
      VELOX_DEPENDENCY_SOURCE: SYSTEM
    steps:
      - uses: actions/checkout@v5
        with:
          fetch-depth: 0
          persist-credentials: false

      - name: Download changed files
        uses: actions/download-artifact@v4
        with:
          name: changed-files

      - uses: ./.github/actions/generate-dependency-graph

      - name: Run impact detection
        run: |
          python3 .github/scripts/detect-build-impact.py \
            --graph dependency-graph.json \
            --changed-files changed_files.txt \
            --build-type release \
            --graph-source "Slow path • Graph generated from PR branch" \
            --output comment.md

      - name: Upload comment
        uses: actions/upload-artifact@v4
        with:
          name: build-impact-comment
          path: comment.md