Config Formatter

A modular CLI tool for formatting YAML configuration files with consistent indentation and directive ordering. Currently supports Docker Compose and Traefik configurations.

Features

• Multi-Format Support: Automatically detects and formats different config types
  • Docker Compose files
  • Traefik configuration files
  • Extensible architecture for adding more formats
• Auto-Detection: Automatically identifies config type based on filename and content
• Consistent Indentation: Configurable space-based indentation (default: 2 spaces)
• Smart Directive Ordering: Format-specific ordering rules for better readability
• Comment Preservation: Comments are preserved in their original positions
• Multiple Output Options: Print to stdout, write to file, or modify in-place
• Format Checking: Verify if files are already formatted

Installation

go install github.com/awsqed/config-formatter@latest

Or build from source:

git clone https://github.com/awsqed/config-formatter
cd config-formatter
go build -o config-formatter

Usage

Basic Usage

Format a file and print to stdout (auto-detects format):

config-formatter -input docker-compose.yml
config-formatter -input traefik.yml

Specify Format Type

config-formatter -input myfile.yml -type docker-compose
config-formatter -input myfile.yml -type traefik

Write to Output File

config-formatter -input docker-compose.yml -output formatted.yml

Format In-Place

config-formatter -input docker-compose.yml -w

Custom Indentation

config-formatter -input traefik.yml -indent 4

Check if File is Formatted

config-formatter -input docker-compose.yml -check

This will exit with code 0 if the file is formatted, or 1 if it needs formatting.

Command-Line Flags

• -input (required): Input config file path
• -output: Output file path (if not specified, prints to stdout)
• -w: Write result to source file instead of stdout
• -indent: Number of spaces for indentation (default: 2)
• -check: Check if file is formatted without making changes
• -type: Formatter type to use (docker-compose, traefik). Auto-detected if not specified

Supported Formats

Docker Compose

Formats Docker Compose files with best-practice directive ordering.

Top-Level Directives:

1. version
2. name
3. networks
4. volumes
5. configs
6. secrets
7. services (placed last as it's typically the longest section)

Service-Level Directives:

1. image
2. build
3. container_name
4. hostname
5. command
6. entrypoint
7. environment
8. env_file
9. ports
10. expose
11. volumes
12. networks
13. depends_on
14. And many more...

Example:

Before formatting:

services:
  web:
    ports:
      - "8080:80"
    image: nginx:latest
    volumes:
      - ./html:/usr/share/nginx/html
    restart: always
networks:
  default:

After formatting:

networks:
  default:

services:
  web:
    image: nginx:latest
    ports:
      - "8080:80"
    volumes:
      - ./html:/usr/share/nginx/html
    restart: always

Traefik

Formats Traefik configuration files with logical grouping and ordering.

Top-Level Directives:

1. Global configuration (log, api, metrics, etc.)
2. entryPoints
3. providers
4. certificatesResolvers
5. Protocol sections (http, tcp, udp, tls)

HTTP Section:

1. routers
2. services
3. middlewares
4. serversTransports

Keys not in the predefined order are sorted alphabetically within their group.

Architecture

The formatter uses a modular plugin architecture:

• formatter/formatter.go: Core interface and base functionality
• modules/dockercompose/: Docker Compose formatter implementation
• modules/traefik/: Traefik formatter implementation

Adding New Formatters

To add support for a new config format:

1. Create a new module directory under modules/
2. Implement the Formatter interface:
   • Format(data []byte, indent int) ([]byte, error) - Format the config
   • Name() string - Return formatter name
   • CanHandle(filename string, data []byte) bool - Detect if file matches this format
3. Register the formatter in main.go

Development

Running Without Building

go run main.go -input compose.yml
go run main.go -input traefik.yml -type traefik

Building for Multiple Platforms

Build for all platforms:

make build-all

Build for specific platforms:

make build-linux-amd64
make build-darwin-arm64
make build-windows-amd64

See all available commands:

make help

Testing

Run tests:

make test

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

To contribute a new formatter module:

1. Implement the Formatter interface
2. Add detection logic in CanHandle()
3. Define format-specific ordering rules
4. Update this README with format documentation

License

MIT