axum-htmx

axum-htmx is a small extension library providing extractors, responders, and request guards for htmx headers within axum.

Table of Contents

• axum-htmx
  • Table of Contents
  • Getting Started
  • Extractors
  • Responders
    • Vary Responders
  • Auto Caching Management
  • Request Guards
  • Examples
    • Example: Extractors
    • Example: Responders
    • Example: Router Guard
  • Feature Flags
  • Contributing
    • Testing
  • License

Getting Started

Run cargo add axum-htmx to add the library to your project.

Extractors

All of the htmx request headers have a supported extractor. Extractors are infallible, meaning they will always succeed and never return an error. In the case where a header is not present, the extractor will return None or false dependant on the expected return type.

Responders

All of the htmx response headers have a supported responder. A responder is a basic type that implements IntoResponseParts, allowing you to simply and safely apply the HX-* headers to any of your responses.

Vary Responders

Also, there are corresponding cache-related headers, which you may want to add to GET responses, depending on the htmx headers.

For example, if your server renders the full HTML when the HX-Request header is missing or false, and it renders a fragment of that HTML when HX-Request: true, you need to add Vary: HX-Request. That causes the cache to be keyed based on a composite of the response URL and the HX-Request request header - rather than being based just on the response URL.

Refer to caching htmx docs section for details.

Look at the Auto Caching Management section for automatic Vary headers management.

Auto Caching Management

Requires feature auto-vary.

Manual use of Vary Reponders adds fragility to the code, because of the need to manually control correspondence between used extractors and the responders.

We provide a middleware to address this issue by automatically adding Vary headers when corresponding extractors are used. For example, on extracting HxRequest, the middleware automatically adds Vary: hx-request header to the response.

Look at the usage example.

Request Guards

Requires feature guards.

In addition to the extractors, there is also a route-wide layer request guard for the HX-Request header. This will redirect any requests without the header to "/" by default.

It should be noted that this is NOT a replacement for an auth guard. A user can trivially set the HX-Request header themselves. This is merely a convenience for preventing users from receiving partial responses without context. If you need to secure an endpoint you should be using a proper auth system.

Examples

Example: Extractors

In this example, we'll look for the HX-Boosted header, which is set when applying the hx-boost attribute to an element. In our case, we'll use it to determine what kind of response we send.

When is this useful? When using a templating engine, like minijinja, it is common to extend different templates from a _base.html template. However, htmx works by sending partial responses, so extending our _base.html would result in lots of extra data being sent over the wire.

If we wanted to swap between pages, we would need to support both full template responses and partial responses (as the page can be accessed directly or through a boosted anchor), so we look for the HX-Boosted header and extend from a _partial.html template instead.

use axum::response::IntoResponse;
use axum_htmx::HxBoosted;

async fn get_index(HxBoosted(boosted): HxBoosted) -> impl IntoResponse {
    if boosted {
        // Send a template extending from _partial.html
    } else {
        // Send a template extending from _base.html
    }
}

Example: Responders

We can trigger any event being listened to by the DOM using an htmx trigger header.

use axum_htmx::HxResponseTrigger;

// When we load our page, we will trigger any event listeners for "my-event.
async fn index() -> (HxResponseTrigger, &'static str) {
    // Note: As HxResponseTrigger only implements `IntoResponseParts`, we must
    // return our trigger first here.
    (
        HxResponseTrigger::normal(["my-event", "second-event"]),
        "Hello, world!",
    )
}

htmx also allows arbitrary data to be sent along with the event, which we can use via the serde feature flag and the HxEvent type.

use serde_json::json;

// Note that we are using `HxResponseTrigger` from the `axum_htmx::serde` module
// instead of the root module.
use axum_htmx::{HxEvent, HxResponseTrigger};

async fn index() -> (HxResponseTrigger, &'static str) {
    let event = HxEvent::new_with_data(
        "my-event",
        // May be any object that implements `serde::Serialize`
        json!({"level": "info", "message": {
            "title": "Hello, world!",
            "body": "This is a test message.",
        }}),
    )
    .unwrap();

    // Note: As HxResponseTrigger only implements `IntoResponseParts`, we must
    // return our trigger first here.
    (HxResponseTrigger::normal([event]), "Hello, world!")
}

Example: Router Guard

use axum::Router;
use axum_htmx::HxRequestGuardLayer;

fn router_one() -> Router {
    Router::new()
        // Redirects to "/" if the HX-Request header is not present
        .layer(HxRequestGuardLayer::default())
}

fn router_two() -> Router {
    Router::new()
        .layer(HxRequestGuardLayer::new("/redirect-to-this-route"))
}

Feature Flags

Contributing

Contributions are always welcome! If you have an idea for a feature or find a bug, let me know. PR's are appreciated, but if it's not a small change, please open an issue first so we're all on the same page!

Testing

cargo +nightly test --all-features

License

axum-htmx is dual-licensed under either

• MIT License
• Apache License, Version 2.0

at your option.