SnapCLI.DataAnnotations 1.0.0-pre

SnapCLI.DataAnnotations

This extension for the SnapCLI🗗 library enables validation of command-line arguments using DataAnnotations🗗 validation attributes. It allows you to ensure that command-line input meets specified criteria before executing the command.

Prerequisite

Your CLI application must be built using the SnapCLI🗗 library and its API.

Usage

To enable validation, add the following code to your CLI application:

using SnapCLI;

[Startup]
public static void Startup()
{
    CLI.BeforeCommand += (args) => args.ParseResult.ValidateDataAnnotations();
}

With this code, any argument or option declared with the SnapCLI API and annotated with validation attributes will be validated before the command is executed.

If validation fails, a ValidationException🗗 will be thrown, detailing the failed option or argument. Note that the CLI application may implement a custom exception handler to process exceptions according to the application's needs.

Validation Attributes

The System.ComponentModel.DataAnnotations🗗 library provides a variety of validation attributes, such as [Range], [StringLength], and [FileExtensions], that can be used for argument validation. Note that the System.ComponentModel.DataAnnotations NuGet package must be installed in your project to utilize these attributes.

Additionally, the SnapCLI.DataAnnotations namespace provides several extra validation attributes useful for command-line arguments validation:

• [FileExists]
• [FileNotExists]
• [DirectoryExists]
• [DirectoryNotExists]

Example

The sample code below demonstrates the usage of various validation attributes, including custom validation via the [CustomValidation]🗗 attribute.

using SnapCLI;
using SnapCLI.DataAnnotations;
using System.ComponentModel.DataAnnotations;

[Startup]
public static void Startup()
{
    // enable validation
    CLI.BeforeCommand += (args) => args.ParseResult.ValidateDataAnnotations();
}

[Command(name: "quotes read", description: "Read and display the file.")]
public static async Task ReadQuotesFile(
    [Argument(name: "file", description: "File containing quotes")]
    [FileExtensions(Extensions = "txt,quotes")]
    [FileExists]
    [CustomValidation(typeof(FileCustomValidation), "FileNotEmpty")]
    FileInfo file,

    [Option(description: "Delay between lines, specified as milliseconds per character in a line.")]
    [Range(0, 1000)]
    int delay = 42,

    [Option(name: "fgcolor", description: "Foreground color of text displayed on the console.")]
    [AllowedValues(ConsoleColor.White, ConsoleColor.Red, ConsoleColor.Blue, ConsoleColor.Green)]
    ConsoleColor fgColor = ConsoleColor.White)
{
    Console.ForegroundColor = fgColor;
    foreach (string line in File.ReadLines(file.FullName))
    {
        Console.WriteLine(line);
        await Task.Delay(delay * line.Length);
    };
}

public static class FileCustomValidation
{
    public static ValidationResult FileNotEmpty(object? obj)
    {
        ArgumentNullException.ThrowIfNull(obj);
        if (obj is string s)
            obj = new FileInfo(s);
        if (obj is not FileInfo fileInfo)
            throw new NotSupportedException($"FileNotEmpty validation doesn't support {obj.GetType()}");
        if (!fileInfo.Exists)
            return new ValidationResult($"File {fileInfo.FullName} doesn't exist");
        if (fileInfo.Length == 0)
            return new ValidationResult($"File {fileInfo.FullName} is empty");
        return ValidationResult.Success!;
    }
}

NuGet Package

The library is available as a NuGet package:

• SnapCLI.DataAnnotations🗗

License

This project is licensed under the MIT License.