CobraFlags

cobraflags is a Go module that provides an integration layer between Cobra CLI applications and Viper configuration management. It automates the binding of environment variables to Cobra command flags, simplifying the process of managing configurations in CLI applications.

Features

• Automatic binding of environment variables to Cobra flags.
• Support for persistent and non-persistent flags.
• Validation of flag values using custom validation functions.
• Easy integration with Cobra commands and subcommands.

Installation

To install the package, use:

go get github.com/go-extras/cobraflags

Usage

Registering Flags

You can define and register flags using the provided IntFlag and StringFlag types. For example:

import (
	"github.com/spf13/cobra"
	"github.com/go-extras/cobraflags"
)

var myFlag = &cobraflags.IntFlag{
	Name:     "example-flag",
	Usage:    "An example integer flag",
	Value:    42,
	Required: true,
}

func main() {
	cmd := &cobra.Command{
		Use:   "myapp",
		Short: "An example application",
		Run: func(cmd *cobra.Command, args []string) {
			value := myFlag.GetInt()
			fmt.Println("Flag value:", value)
		},
	}

	myFlag.Register(cmd)
	cobraflags.CobraOnInitialize("MYAPP", cmd)

	if err := cmd.Execute(); err != nil {
		fmt.Println(err)
	}
}

Environment Variable Binding

Flags are automatically bound to environment variables using the provided prefix. For example, a flag named example-flag with the prefix MYAPP will be bound to the environment variable MYAPP_EXAMPLE_FLAG.

Custom Viper Keys

By default, flags use their name as the Viper configuration key. You can customize this by setting the ViperKey field:

myFlag := &cobraflags.StringFlag{
    Name:     "config-file",
    ViperKey: "app.config.file", // Custom Viper key
    Usage:    "Path to configuration file",
    Value:    "config.yaml",
}

This allows you to:

• Use different configuration keys than flag names
• Support nested configuration structures
• Maintain backward compatibility when renaming flags

If ViperKey is empty, the flag will fall back to using its Name for Viper binding.

Validation

You can add custom validation logic for flags using the ValidateFunc field:

myFlag.ValidateFunc = func(value int) error {
	if value < 0 {
		return fmt.Errorf("value must be non-negative")
	}
	return nil
}

You can also use the Validator field to provide a custom validator that implements the cobraflags.Validator interface:

myFlag.Validator = cobraflags.ValidatorFunc[int](func(value int) error {
	if value < 0 {
		return fmt.Errorf("value must be non-negative")
	}
	return nil
})

Note: cobraflags.ValidatorFunc is used for demonstration purposes only, use your own validators.

Documentation

For detailed documentation, refer to the source code and comments in the package.

License

This project is licensed under the MIT License. See the LICENSE file for details.