maud-extensions

Small, local superpowers for Maud.

Install

cargo add maud-extensions

If you want the experimental component system too:

cargo add maud-extensions --features components

If you want the crate to read as mx::... at call sites without renaming the published crate:

cargo add maud-extensions --rename mx

or in Cargo.toml:

[dependencies]
mx = { package = "maud-extensions", version = "0.6.0" }

Core Story

Write plain html! and emit local CSS and JS where they belong:

use maud::html;
use maud_extensions::{css, js};

fn status_card(message: &str) -> maud::Markup {
    html! {
        article class="status-card" {
            h2 { "System status" }
            p class="message" { (message) }

            (css! {
                me {
                    border: 1px solid #ddd;
                    border-radius: 10px;
                    padding: 12px;
                }
                me.ready {
                    border-color: #16a34a;
                }
            })

            (js!(once, {
                me().class_add("ready");
            }))
        }
    }
}

This is still the intended center of gravity:

• no wrapper component macro
• no hidden CSS/JS injection
• no stringly helper names
• plain Maud remains the main language

Experimental Components

The component system is opt-in behind the components feature.

Preferred authoring pattern:

use maud::{Markup, Render};
use maud_extensions::{self as mx, Component, Slot};

#[derive(Component)]
struct Card {
    title: String,
    header: Slot<Markup>,
    #[mx(default)]
    body: Slot<Markup>,
    footer: Slot<Markup>,
    #[mx(each = action)]
    actions: Slot<Vec<Markup>>,
}

#[mx::component]
impl Card {
    css! {
        me {
            padding: 1rem;
            border: 1px solid #ddd;
        }

        me .actions {
            display: flex;
            gap: 0.5rem;
        }
    }

    js!(once, {
        me().class_add("ready");
    });

    render! {
        article.card {
            header class="header" { (self.header) }
            h2 { (self.title) }
            div.body { (self.body) }
            footer class="footer" { (self.footer) }
            div.actions { (self.actions) }
        }
    }
}

impl Render for Card {
    fn render(&self) -> Markup {
        mx::ComponentRender::__mx_render(self)
    }
}

fn view() -> Markup {
    Card::new()
        .title("Profile")
        .header(maud::html! { span { "Welcome" } })
        .child(maud::html! { p { "Body" } })
        .footer(maud::html! { button { "Save" } })
        .action(maud::html! { button { "Edit" } })
        .render()
}

What this gives you:

• Bon-backed typed builders
• Slot<Markup> and Slot<Vec<Markup>> as the slot declaration path
• #[mx(default)] for the single default slot
• #[mx::component] impl blocks with colocated:
  • render! { ... }
  • css! { ... }
  • js!(once, { ... })
• builder .render() automatically includes impl-local CSS and JS in the rendered root

Current constraints:

• use Slot<T> instead of #[mx(slot)]
• if there are multiple slot fields, mark exactly one #[mx(default)]
• repeated slots use Slot<Vec<T>> plus #[mx(each = item_name)]
• #[mx::component] impls currently allow:
  • exactly one render!
  • at most one css!
  • at most one js!

Mental model:

• #[derive(Component)] owns fields, slots, and the Bon-backed builder
• #[mx::component] owns the render root and colocated CSS/JS blocks
• builder .render() goes through the hidden ComponentRender hook produced by the impl macro

This keeps the builder and the impl-local render/assets story explicit without requiring manual (Self::css()) / (Self::js()) emission in the render body.

If you want a more minimal component style, you can still stop at plain html! + css! + js!. The component system is intentionally a second layer, not the only way to use the crate.

Named Helpers

When reuse helps, define local helper functions with Rust identifiers:

use maud::html;
use maud_extensions::{css, js};

css!(card_css, {
    me { gap: px!(12); }
});

js!(card_js, once, {
    me().class_add("ready");
});

fn card() -> maud::Markup {
    html! {
        article.card {
            (card_css())
            (card_js())
            "Hello"
        }
    }
}

Supported css! forms:

• css! { ... }
• css!(name, { ... })

Supported js! forms:

• js! { ... }
• js!(once, { ... })
• js!(name, { ... })
• js!(name, once, { ... })

CSS Helper Macros

Inside css! token mode you can use:

• raw!(r#"..."#)
• media!(prelude, { ... })
• container!(prelude, { ... })
• supports!(prelude, { ... })
• layer!(prelude, { ... })
• keyframes!(prelude, { ... })
• unit helpers:
  • rem!(...)
  • em!(...)
  • px!(...)
  • pct!(...)
  • vw!(...)
  • vh!(...)
  • ms!(...)
  • s!(...)

Example:

use maud_extensions::css;

fn responsive_styles() -> maud::Markup {
    css! {
        media!("(min-width: 48rem)", {
            me { padding: rem!(2); }
        })
        supports!("(display: grid)", {
            me { gap: px!(12); }
        })
    }
}

Limits

• css! and js! are placement-sensitive local emitters
• js!(once, ...) relies on a data-mx-js-ran marker on the parent element
• CSS token mode only sees Rust-tokenizable input; use raw!(...) for arbitrary CSS fragments
• JavaScript is validated with SWC before emission
• CSS is checked for lightweight syntax and raw-text safety before emission