This article will introduce how to trigger build tasks only for specific directories when modifying them in a Monorepo scenario, avoiding full builds to prevent resource waste and time consumption.

Key Concepts

• Syntax guide: Pipeline.ifModify
• System default environment variables: CNB_PIPELINE_KEY

Example Configuration

.docker-build-pipeline:
  &docker-build-pipeline # Use YAML anchors for configuration reuse
  - services:
      - docker # After declaration, docker commands can be used directly in the pipeline
    ifModify:
      - packages/${CNB_PIPELINE_KEY}/** # Specify that only modifications to files in this directory trigger the build. CNB_PIPELINE_KEY is a system default environment variable representing the current pipeline's KEY
    stages:
      - name: set docker tag
        script: echo -n "${CNB_DOCKER_REGISTRY}/${CNB_REPO_SLUG_LOWERCASE}:$CODING_COMMIT_SHORT"
        exports:
          info: IMAGE_TAG

      - name: docker build
        script: cd packages/${CNB_PIPELINE_KEY} && docker build -t $IMAGE_TAG .

      - name: push image
        script: docker push $IMAGE_TAG

main:
  push:
    package-1: *docker-build-pipeline
    package-2: *docker-build-pipeline