Uncrustify Action

A GitHub Action that runs uncrustify on changed files in pull requests and pushes to check code formatting. Features automatic file discovery, configurable exclude patterns, version-specific uncrustify builds with caching.

Features

• 🚀 Fast: Caches compiled uncrustify binaries for quick subsequent runs
• 🎯 Smart: Only processes files that have changed in PRs/pushes
• 🔧 Safe: Check-only mode - never modifies your code
• 📁 Configurable: Custom file extensions and exclude patterns
• 🏷️ Version-specific: Pin to exact uncrustify versions
• ✨ Zero-config: Works with standard uncrustify.cfg in repo root

Usage

name: Code Format Check

on:
  pull_request:
    branches: [main]

jobs:
  format-check:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          submodules: false

      - name: Check C/C++ formatting
        uses: openmv/uncrustify-action@v1
        with:
          config-path: 'tools/my-uncrustify.cfg'    # optional, defaults to 'uncrustify.cfg'
          extensions: 'c,h,cpp,hpp'                 # required
          exclude-patterns: |                      # optional
            lib/**
            vendor/**
          uncrustify-version: '0.75.0'             # required
          fail-on-error: 'true'                    # required: 'true' or 'false'

Inputs

Input	Description	Required	Default
config-path	Path to uncrustify config file	No	uncrustify.cfg
extensions	File extensions to check (comma-separated)	Yes	-
exclude-patterns	Patterns to exclude (YAML list, supports glob)	No	-
fail-on-error	Whether to fail if formatting issues found	Yes	-
uncrustify-version	Uncrustify version to use (e.g., "0.75.0")	Yes	-

Outputs

Output	Description
files-changed	Number of files that needed formatting
formatting-needed	Whether any files needed formatting (true/false)

Exclude Patterns

The exclude-patterns input supports glob-style patterns as a YAML list:

exclude-patterns: |
  lib/**
  vendor/**
  *.generated.c
  build/**

Common patterns:

• lib/** - Exclude entire lib directory
• vendor/** - Exclude vendor/third-party code
• *.generated.* - Exclude generated files
• build/** - Exclude build artifacts

Troubleshooting

Config file not found

Ensure your uncrustify.cfg exists in the repository root, or specify the correct path with config-path.

No files processed

Check that:

• File extensions match your extensions input
• Files aren't excluded by exclude-patterns
• Files were actually changed in the commit/PR

Build failures

The action builds uncrustify from source. If builds fail:

• Check the uncrustify version exists
• Ensure the runner has sufficient resources
• Check for any CMake-related errors in the logs

License

This action is distributed under the MIT License. See LICENSE for more information.