paths-filter/README.md

<p align="center">
  <a href="https://github.com/dorny/pr-changed-files-filter/actions"><img alt="typescript-action status" src="https://github.com/dorny/pr-changed-files-filter/workflows/build-test/badge.svg"></a>
</p>

**CAUTION**: This action can be only used in a workflow triggered by `pull_request` event.

# Pull request changed files filter

This [Github Action](https://github.com/features/actions) enables conditional execution of workflow job steps considering which files are modified by a pull request.

It saves time and resources especially in monorepo setups, where you can run slow tasks (e.g. integration tests) only for changed components.
Github workflows built-in
[path filters](https://help.github.com/en/actions/referenceworkflow-syntax-for-github-actions#onpushpull_requestpaths)
doesn't allow this because they doesn't work on a level of individual jobs or steps.

## Usage

The action accepts filter rules in the YAML format.
Each filter rule is a list of [glob expressions](https://github.com/isaacs/minimatch).
Corresponding output variable will be created to indicate if there's a changed file matching any of the rule glob expressions.
Output variables can be later used in the `if` clause to conditionally run specific steps.

### Inputs
- **`githubToken`**: GitHub Access Token - use `${{ github.token }}`
- **`filters`**: YAML dictionary where keys specifies rule names and values are lists of file path patterns

### Outputs
- For each rule it sets output variable named by the rule to text:
   - `'true'` - if **any** of changed files matches any of rule patterns
   - `'false'` - if **none** of changed files matches any of rule patterns


### Sample workflow
```yaml
...
name: Build verification

on:
  pull_request:
    types:
      - opened
      - edited
      - synchronize
    branches:
      - master
jobs:
  tests:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v2
    - uses: dorny/pr-changed-files-filter@v1
      id: filter
      with:
        githubToken: ${{ github.token }}
        filters: |
          backend:
            - 'backend/**/*'
          frontend:
            - 'frontend/**/*'

    # run only if 'backend' files were changed
    - name: backend unit tests
      if: steps.filter.outputs.backend == 'true'
      run: ...

    # run only if 'frontend' files were changed
    - name: frontend unit tests
      if: steps.filter.outputs.frontend == 'true'
      run: ...

    # run if 'backend' or 'frontend' files were changed
    - name: e2e tests
      if: steps.filter.outputs.backend == 'true' || steps.filter.outputs.frontend == 'true'
      run: ...
```

## How it works

1. Required inputs are checked (`githubToken` & `filters`)
2. Provided access token is used to fetch list of changed files.
3. For each filter rule it checks if there is any matching file
4. Output variables are set

## Difference from related projects:

- [Has Changed Path](https://github.com/MarceloPrado/has-changed-path)
  - detects changes from previous commit
  - you have to configure `checkout` action to fetch some number of previous commits
  - `git diff` is used for change detection
  - outputs only single `true` / `false` value if any of provided paths contains changes
- [Changed Files Exporter](https://github.com/futuratrepadeira/changed-files)
  - outputs lists with paths of created, updated and deleted files
  - output is not directly usable in the `if` clause
- [Changed File Filter](https://github.com/tony84727/changed-file-filter)
  - allows change detection between any refs or commits
  - fetches whole history of your git repository
  - might have negative performance impact on big repositories (github by default fetches only single commit)