<a href="https://bon-rs.com/guide/overview">    <img        src="https://bon-rs.com/bon-home.png"        alt="bon home"    /></a><div align="center">    <a href="https://github.com/elastio/bon"><img        alt="github"        src="https://img.shields.io/badge/github-elastio/bon-228b22?style=for-the-badge&labelColor=555555&logo=github"        height="25"    /></a>    <a href="https://crates.io/crates/bon"><img        alt="crates.io"        src="https://img.shields.io/crates/v/bon.svg?style=for-the-badge&color=e37602&logo=rust"        height="25"    /></a>    <a href="https://docs.rs/bon/latest/bon/"><img        alt="docs.rs"        src="https://img.shields.io/badge/docs.rs-bon-3b74d1?style=for-the-badge&labelColor=555555&logo=docs.rs"        height="25"    /></a>        <a href="https://docs.rs/bon/latest/bon/"><img        alt="docs.rs"        src="https://img.shields.io/badge/MSRV-1.59.0-b83fbf?style=for-the-badge&labelColor=555555&logo=docs.rs"        height="25"    /></a></div><br/><div align="center">    <table>        <tbody>            <tr>                <td><a href="https://bon-rs.com/guide/overview">📖 Guide Book</a></td>                <td>Narrative introduction</td>            </tr>            <tr>                <td><a href="https://bon-rs.com/reference/builder">🔍 API Reference</a></td>                <td>Attributes API index</td>            </tr>        </tbody>    </table></div><!-- #region overview --># Overview`bon` is a Rust crate for generating compile-time-checked builders for structs and functions. It also provides idiomatic partial application with optional and named parameters for functions and methods.If you wonder "Why would I use builders?", see the [motivational blog post](https://bon-rs.com/blog/how-to-do-named-function-arguments-in-rust).## Function BuilderYou can turn a function with positional parameters into a function with named parameters with `#[builder]`.```rustuse bon::builder;#[builder]fn greet(name: &str, level: Option<u32>) -> String {    let level = level.unwrap_or(0);    format!("Hello {name}! Your level is {level}")}let greeting = greet()    .name("Bon")    .level(24) // <- setting `level` is optional, we could omit it    .call();assert_eq!(greeting, "Hello Bon! Your level is 24");```Any syntax for functions is supported including `async`, fallible, generic functions, `impl Trait`, etc.Many things are customizable with additional attributes described in the [API reference](https://bon-rs.com/reference/builder), but let's see what else `bon` has to offer.## Struct BuilderUse `#[derive(Builder)]` to generate a builder for a struct.```rustuse bon::Builder;#[derive(Builder)]struct User {    name: String,    is_admin: bool,    level: Option<u32>,}let user = User::builder()    .name("Bon".to_owned())    // `level` is optional, we could omit it here    .level(24)    // call setters in any order    .is_admin(true)    .build();assert_eq!(user.name, "Bon");assert_eq!(user.level, Some(24));assert!(user.is_admin);```## Method BuilderAssociated methods require `#[bon]` on top of the impl block additionally.### Method `new`The method named `new` generates `builder()/build()` methods.```rustuse bon::bon;struct User {    id: u32,    name: String,}#[bon]impl User {    #[builder]    fn new(id: u32, name: String) -> Self {        Self { id, name }    }}let user = User::builder()    .id(1)    .name("Bon".to_owned())    .build();assert_eq!(user.id, 1);assert_eq!(user.name, "Bon");````#[derive(Builder)]` on a struct generates builder API that is fully compatible with placing `#[builder]` on the `new()` method with a signature similar to the struct's fields (more details on the [Compatibility](https://bon-rs.com/guide/basics/compatibility#switching-between-derive-builder-and-builder-on-the-new-method) page).### Other MethodsAll other methods generate `{method_name}()/call()` methods.```rustuse bon::bon;struct Greeter {    name: String,}#[bon]impl Greeter {    #[builder]    fn greet(&self, target: &str, prefix: Option<&str>) -> String {        let prefix = prefix.unwrap_or("INFO");        let name = &self.name;        format!("[{prefix}] {name} says hello to {target}")    }}let greeter = Greeter { name: "Bon".to_owned() };let greeting = greeter    .greet()    .target("the world")    // `prefix` is optional, omitting it is fine    .call();assert_eq!(greeting, "[INFO] Bon says hello to the world");```Methods with or without `self` are both supported.## No Panics PossibleBuilders generated by `bon`'s macros use the typestate pattern to ensure all required parameters are filled, and the same setters aren't called repeatedly to prevent unintentional overwrites. If something is wrong, a compile error will be created.| ⭐ Don't forget to give our repo a [star on Github ⭐](https://github.com/elastio/bon)! || --------------------------------------------------------------------------------------- |## What's Next?What you've seen above is the first page of the 📖 Guide Book. If you want to learn more, jump to the [Basics](https://bon-rs.com/guide/basics) section. And remember: knowledge is power 🐱!Feel free to jump to code and use the `#[builder]` and `#[derive(Builder)]` once you've seen enough docs to get started.The [🔍 API Reference](https://bon-rs.com/reference/builder) will help you navigate the attributes once you feel comfortable with the basics of `bon`. Both `#[derive(Builder)]` on structs and `#[builder]` on functions/methods have almost identical attributes API, so the documentation for them is common.## InstallationAdd `bon` to your `Cargo.toml`.<!-- If you change this, make sure to update `scripts/sync-version.sh` -->```toml[dependencies]bon = "3.9"```You can opt out of `std` and `alloc` cargo features with `default-features = false` for `no_std` environments.See [alternatives](https://bon-rs.com/guide/alternatives) for comparison.## Getting HelpIf you can't figure something out, consult the docs and maybe use the `🔍 Search` bar on our [docs website](https://bon-rs.com). You may also create an issue or a discussion on the [Github repository](https://github.com/elastio/bon) for help or write us a message on [Discord](https://bon-rs.com/discord).## Socials<table><tbody>    <tr>        <td><a href="https://bon-rs.com/discord">Discord</a></td>        <td>Here you can leave feedback, ask questions, report bugs, etc.</td>    </tr></tbody></table>## AcknowledgmentsThis project was heavily inspired by such awesome crates as [`buildstructor`](https://docs.rs/buildstructor), [`typed-builder`](https://docs.rs/typed-builder) and [`derive_builder`](https://docs.rs/derive_builder). This crate was designed with many lessons learned from them.## Supporters<div align="center">Big thanks to `bon`'s current financial supporters ❤️**Julius Lungys**\<sup><code>$1/month</code></sup></div>## Past Supporters<div align="center">Big thanks to `bon`'s past financial supporters ❤️[![](https://github.com/user-attachments/assets/b0acb844-4b91-461c-95ae-90a601296500)](https://kindness.ai)\[**Kindness**](https://kindness.ai)**Ethan Skowronski**</div>## License<sup>Licensed under either of <a href="https://github.com/elastio/bon/blob/master/LICENSE-APACHE">Apache License, Version2.0</a> or <a href="https://github.com/elastio/bon/blob/master/LICENSE-MIT">MIT license</a> at your option.</sup><br><sub>Unless you explicitly state otherwise, any contribution intentionally submittedfor inclusion in the work by you, as defined in the Apache-2.0 license, shall bedual licensed as above, without any additional terms or conditions.</sub><!-- #endregion overview -->