expand-action

This is an action to expand path patterns by changed files in a pull request.

Motivation

Background

This action provides an alternative of paths trigger for a monorepo (mono repository). Typically a monorepo contains many modules, for example,

monorepo
├── microservice1
├── microservice2
├── ...
├── microserviceN
└── common-policy

GitHub Actions provides paths trigger. In most cases, an owner of microservice creates a workflow for test or build. For example, a workflow for test of Go microservice is like,

name: microservice1--test
on:
  pull_request:
    paths:
      - microservice1/**
jobs:
  lint:
    steps:
      - uses: actions/checkout@v2
      - uses: golangci/golangci-lint-action@v2
  test:
    steps:
      - uses: actions/checkout@v2
      - run: make -C microservice1 test

Problem to solve

It often needs to inspect crosscutting concern against all modules. For example,

• Policy test for Kubernetes manifests
• Security test with common rules

It takes a long time to process all modules if a monorepo has many modules.

Feature: Path variable expansion

This action expands path patterns by changed files in a pull request.

For example, if the following path patterns are given,

paths: |
  :service/manifest/**
outputs: |
  kustomization=:service/manifest/kustomization.yaml

and the following file is changed in a pull request,

microservice1/manifest/deployment.yaml

this action determines the path variable as follows:

":service" => "microservice1"

Finally this action expands the pattern as follows:

microservice1/manifest/kustomization.yaml

It reduces a number of modules to process in a workflow.

Feature: Wildcard fallback

This action may fallback to generate wildcard patterns when the following cases:

• Any pattern in paths did not match
• Any pattern in paths-fallback matched
• Pull request contains more than 1,000 changed files

For example, if the following path patterns are given,

paths: |
  :service/manifest/**
paths-fallback: |
  conftest/**
outputs: |
  kustomization=:service/manifest/kustomization.yaml

and the following file is changed in a pull request,

conftest/policy/foo.rego

this action replaces all path variables with wildcard * as follows:

*/manifest/kustomization.yaml

This allows inspection of all modules if a specific file such as a common policy is changed.

Examples

Usecase: build manifests against changed paths

Let's think a case of monorepo with Kubernetes components. For example,

clusters
├── staging
|   ├── cluster-autoscaler
|   └── coredns
└── production
    └── cluster-autoscaler

To run kustomize build for changed components in a pull request:

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - uses: int128/expand-action@v1
        id: expand
        with:
          paths: |
            clusters/:cluster/:component/**
          outputs: |
            kustomization=clusters/:cluster/:component/kustomization.yaml
      - uses: int128/kustomize-action@v1
        with:
          kustomization: ${{ steps.expand.outputs.kustomization }}

This action expands paths by the following rule:

clusters/:cluster/:component/**
↓
clusters/:cluster/:component/kustomization.yaml

If clusters/staging/cluster-autoscaler/config.yaml is changed in a pull request, the rule would be:

clusters/staging/cluster-autoscaler/**
↓
clusters/staging/cluster-autoscaler/kustomization.yaml

and finally this action sets an output to clusters/staging/cluster-autoscaler/kustomization.yaml.

Inputs

Name	Default	Description
paths	required	Paths to expand
paths-fallback	empty	If any path is changed, fallback to wildcard
outputs	required	Paths to set into outputs in form of NAME=PATH
token	github.token	GitHub token to list files

Outputs

This action sets the names defined by outputs in inputs.