How to use Swift Argument Parser with async/await?

Conform to AsyncParsableCommand instead of ParsableCommand and implement an async run method. The library handles the async context automatically, as shown in the count-lines example in the README.

Swift Argument Parser vs manual CommandLine parsing?

ArgumentParser provides type safety, automatic help, and reduced boilerplate, while manual parsing is more flexible but error-prone and requires custom validation and documentation. For robust tools, ArgumentParser saves time and reduces bugs.

How to create nested subcommands in ArgumentParser?

Define multiple ParsableCommand types and use them as subcommands by declaring properties with @OptionGroup or similar approaches, as demonstrated in the math example with command hierarchies in the repository.

Can I customize the help text format?

Yes, through property wrapper parameters like help in @Option or @Argument, and by overriding methods like help or using custom validation. However, the core formatting is largely fixed, with limited control over layout.

What's the performance overhead of using ArgumentParser?

Minimal for most use cases, as it leverages Swift's compile-time features, but initial parsing and reflection might add slight overhead compared to manual parsing for trivial scripts with very few arguments.

How to handle custom validation and errors?

Implement the validate method in your command or throw errors in the run method. ArgumentParser provides built-in error messages for common issues, but complex validation requires manual implementation.

Open-Awesome

Swift Argument Parser

Apache-2.0Swift1.8.2

A Swift library for building command-line tools with type-safe argument parsing and automatic help generation.

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What is Swift Argument Parser?

Swift Argument Parser is a library for building command-line tools in Swift. It allows developers to define command-line interfaces declaratively using Swift types and property wrappers, automatically handling argument parsing, validation, and help text generation. It solves the problem of manually parsing command-line arguments and writing usage documentation.

Target Audience

Swift developers creating command-line tools, utilities, or scripts that require robust argument handling. This includes tool authors, system administrators, and developers building developer-facing CLI applications.

Value Proposition

Developers choose Swift Argument Parser for its type safety, reduced boilerplate, and seamless integration with Swift's language features. Its automatic help generation and error messaging save development time and improve user experience compared to manual parsing solutions.

Overview

Straightforward, type-safe argument parsing for Swift

Use Cases

Best For

Building Swift-based CLI tools with complex argument structures
Creating command-line utilities that require nested subcommands
Developing tools that need automatic help and usage documentation
Writing async/await enabled command-line applications in Swift
Ensuring type safety and validation for command-line arguments
Rapid prototyping of CLI interfaces with minimal boilerplate code

Not Ideal For

Projects requiring command-line interfaces in languages other than Swift
Tools needing advanced interactive features like real-time autocompletion or GUI integration
Simple scripts with fixed arguments where manual parsing is trivial and adding a dependency is overkill

Pros & Cons

Pros

Type-Safe Parsing

Uses Swift's property wrappers and type system to define arguments, ensuring compile-time safety and reducing runtime errors, as demonstrated in the example with @Option and @Argument decorators.

Automatic Help Generation

Generates detailed usage instructions and error messages automatically based on command structure, shown in the README's help output for the repeat example, saving development time.

Nested Commands Support

Enables complex command hierarchies with subcommands, similar to tools like git, as illustrated in the math example with multiple operations.

Async/Await Integration

Includes AsyncParsableCommand for seamless use with Swift's concurrency model, allowing async command implementations without extra boilerplate, as seen in the count-lines example.

Cons

Swift Ecosystem Lock-in

Exclusively tied to Swift, making it unsuitable for cross-platform tools in other languages or environments without Swift support, limiting its versatility.

Swift Version Constraints

Requires specific minimum Swift versions, as detailed in the supported versions table, which can hinder adoption in teams with older toolchains or strict compatibility needs.

Limited to Parsing Scope

Focuses solely on argument parsing and help generation; lacks built-in features for other CLI aspects like output formatting, interactive prompts, or advanced error handling beyond basic messages.

Frequently Asked Questions

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