classnames-const-rs

A Rust macro library for compile-time CSS class name concatenation and processing.

Features

🚀 Zero runtime overhead - Everything happens at compile time
🧹 Automatic whitespace handling - Removes extra spaces and normalizes whitespace
🔗 Multiple class concatenation - Combine any number of class names
📝 Type-safe - Compile-time string processing with full type safety
🎯 Simple API - Easy to use macro interface

Installation

Add this to your Cargo.toml:

[dependencies]
classnames-const-rs = "0.1.0"

Usage

Basic Usage

use classnames_const_rs::*;

const BUTTON_CLASS: &str = classnames_concat!("btn", "btn-primary");
assert_eq!(BUTTON_CLASS, "btn btn-primary");

Handling Messy Whitespace

The macro automatically handles extra whitespace:

use classnames_const_rs::*;

const MESSY_CLASSES: &str = classnames_concat!("  header ", " main  ", "footer  ");
assert_eq!(MESSY_CLASSES, "header main footer");

Empty Strings

Empty strings are handled gracefully:

use classnames_const_rs::*;

const SPARSE_CLASS: &str = classnames_concat!("", "active", "", "highlight");
assert_eq!(SPARSE_CLASS, "active highlight");

Complex Example

use classnames_const_rs::*;

const BASE_CLASSES: &str = "container mx-auto";
const RESPONSIVE_CLASSES: &str = "md:w-1/2 lg:w-1/3";
const STATE_CLASSES: &str = "hover:bg-blue-500 focus:outline-none";

const COMPONENT_CLASSES: &str = classnames_concat!(
    BASE_CLASSES,
    RESPONSIVE_CLASSES,
    STATE_CLASSES,
    "p-4 rounded-lg"
);

// Result: "container mx-auto md:w-1/2 lg:w-1/3 hover:bg-blue-500 focus:outline-none p-4 rounded-lg"

API Reference

`classnames_concat!`

Concatenates multiple class name strings with automatic whitespace handling.

Syntax:

classnames_concat!(class1, class2, ..., classN)

Features:

Removes leading and trailing whitespace
Collapses multiple consecutive spaces into single spaces
Handles empty strings gracefully
Works with any number of arguments

`trim_format!`

Internal macro for whitespace normalization. Generally not needed for direct use.

Use Cases

This library is perfect for:

🎨 CSS-in-Rust applications where you need to build class strings
🌐 Web frameworks that generate HTML with dynamic classes
📱 UI libraries that combine multiple styling concerns
🔧 Build-time optimizations where class strings are known at compile time

Performance

Since all processing happens at compile time, there is zero runtime overhead. The resulting strings are embedded directly into your binary as static string literals.

Contributing

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

License

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

Acknowledgments

Built on top of the excellent constcat crate for compile-time string concatenation
Inspired by the JavaScript classnames library

classnames-const-rs 0.1.0