axum-htmx/README.md

axum-htmx

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

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.

Header	Extractor	Value
HX-Boosted	HxBoosted	bool
HX-Current-URL	HxCurrentUrl	Option<axum::http::Uri>
HX-History-Restore-Request	HxHistoryRestoreRequest	bool
HX-Prompt	HxPrompt	Option<String>
HX-Request	HxRequest	bool
HX-Target	HxTarget	Option<String>
HX-Trigger-Name	HxTriggerName	Option<String>
HX-Trigger	HxTrigger	Option<String>

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.

Header	Responder	Value
HX-Location	HxLocation	axum::http::Uri
HX-Push-Url	HxPushUrl	axum::http::Uri
HX-Redirect	HxRedirect	axum::http::Uri
HX-Refresh	HxRefresh	bool
HX-Replace-Url	HxReplaceUrl	axum::http::Uri
HX-Reswap	HxReswap	axum_htmx::responders::SwapOption
HX-Retarget	HxRetarget	String
HX-Reselect	HxReselect	String
HX-Trigger	HxResponseTrigger	axum_htmx::serde::HxEvent
HX-Trigger-After-Settle	HxResponseTrigger	axum_htmx::serde::HxEvent
HX-Trigger-After-Swap	HxResponseTrigger	axum_htmx::serde::HxEvent

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.

Header	Responder
Vary: HX-Request	VaryHxRequest
Vary: HX-Target	VaryHxTarget
Vary: HX-Trigger	VaryHxTrigger
Vary: HX-Trigger-Name	VaryHxTriggerName

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

Flag	Default	Description	Dependencies
auto-vary	Disabled	A middleware to address htmx caching issue	futures, tokio, tower
guards	Disabled	Adds request guard layers.	tower, futures-core, pin-project-lite
serde	Disabled	Adds serde support for the HxEvent and LocationOptions	serde, serde_json

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.