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#![deny(missing_docs)]
#![forbid(unsafe_code)]
//! # Leptos Meta
//!
//! Leptos Meta allows you to modify content in a document’s `<head>` from within components
//! using the [`Leptos`](https://github.com/leptos-rs/leptos) web framework.
//!
//! Document metadata is updated automatically when running in the browser. For server-side
//! rendering, after the component tree is rendered to HTML, [`MetaContext::dehydrate`] can generate
//! HTML that should be injected into the `<head>` of the HTML document being rendered.
//!
//! ```
//! use leptos::*;
//! use leptos_meta::*;
//!
//! #[component]
//! fn MyApp() -> impl IntoView {
//! // Provides a [`MetaContext`], if there is not already one provided.
//! provide_meta_context();
//!
//! let (name, set_name) = create_signal("Alice".to_string());
//!
//! view! {
//! <Title
//! // reactively sets document.title when `name` changes
//! text=move || name.get()
//! // applies the `formatter` function to the `text` value
//! formatter=|text| format!("“{text}” is your name")
//! />
//! <main>
//! <input
//! prop:value=move || name.get()
//! on:input=move |ev| set_name.set(event_target_value(&ev))
//! />
//! </main>
//! }
//! }
//! ```
//! # Feature Flags
//! - `csr` Client-side rendering: Generate DOM nodes in the browser
//! - `ssr` Server-side rendering: Generate an HTML string (typically on the server)
//! - `hydrate` Hydration: use this to add interactivity to an SSRed Leptos app
//! - `stable` By default, Leptos requires `nightly` Rust, which is what allows the ergonomics
//! of calling signals as functions. Enable this feature to support `stable` Rust.
//!
//! **Important Note:** You must enable one of `csr`, `hydrate`, or `ssr` to tell Leptos
//! which mode your app is operating in.
use cfg_if::cfg_if;
use indexmap::IndexMap;
use leptos::{
leptos_dom::{debug_warn, html::AnyElement},
*,
};
use std::{
cell::{Cell, RefCell},
fmt::Debug,
rc::Rc,
};
#[cfg(any(feature = "csr", feature = "hydrate"))]
use wasm_bindgen::{JsCast, UnwrapThrowExt};
mod body;
mod html;
mod link;
mod meta_tags;
mod script;
mod style;
mod stylesheet;
mod title;
pub use body::*;
pub use html::*;
pub use link::*;
pub use meta_tags::*;
pub use script::*;
pub use style::*;
pub use stylesheet::*;
pub use title::*;
/// Contains the current state of meta tags. To access it, you can use [`use_head`].
///
/// This should generally by provided somewhere in the root of your application using
/// [`provide_meta_context`].
#[derive(Clone, Default, Debug)]
pub struct MetaContext {
/// Metadata associated with the `<html>` element
pub html: HtmlContext,
/// Metadata associated with the `<title>` element.
pub title: TitleContext,
/// Metadata associated with the `<body>` element
pub body: BodyContext,
/// Other metadata tags.
pub tags: MetaTagsContext,
}
/// Manages all of the element created by components.
#[derive(Clone, Default)]
pub struct MetaTagsContext {
next_id: Rc<Cell<MetaTagId>>,
#[allow(clippy::type_complexity)]
els: Rc<
RefCell<
IndexMap<
Oco<'static, str>,
(HtmlElement<AnyElement>, Option<web_sys::Element>),
>,
>,
>,
}
impl core::fmt::Debug for MetaTagsContext {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
f.debug_struct("MetaTagsContext").finish()
}
}
impl MetaTagsContext {
/// Converts metadata tags into an HTML string.
#[cfg(any(feature = "ssr", docs))]
pub fn as_string(&self) -> String {
self.els
.borrow()
.iter()
.map(|(_, (builder_el, _))| {
builder_el.clone().into_view().render_to_string()
})
.collect()
}
#[doc(hidden)]
pub fn register(
&self,
id: Oco<'static, str>,
builder_el: HtmlElement<AnyElement>,
) {
cfg_if! {
if #[cfg(any(feature = "csr", feature = "hydrate"))] {
use leptos::document;
let element_to_hydrate = document()
.get_element_by_id(&id);
let el = element_to_hydrate.unwrap_or_else({
let builder_el = builder_el.clone();
move || {
let head = document().head().unwrap_throw();
head
.append_child(&builder_el)
.unwrap_throw();
(*builder_el).clone().unchecked_into()
}
});
on_cleanup({
let el = el.clone();
let els = self.els.clone();
let id = id.clone();
move || {
let head = document().head().unwrap_throw();
_ = head.remove_child(&el);
els.borrow_mut().swap_remove(&id);
}
});
self
.els
.borrow_mut()
.insert(id, (builder_el.into_any(), Some(el)));
} else {
self.els.borrow_mut().insert(id, (builder_el, None));
}
}
}
}
#[derive(Copy, Clone, Debug, Default, PartialEq, Eq, Hash)]
struct MetaTagId(usize);
impl MetaTagsContext {
fn get_next_id(&self) -> MetaTagId {
let current_id = self.next_id.get();
let next_id = MetaTagId(current_id.0 + 1);
self.next_id.set(next_id);
next_id
}
}
/// Provides a [`MetaContext`], if there is not already one provided. This ensures that you can provide it
/// at the highest possible level, without overwriting a [`MetaContext`] that has already been provided
/// (for example, by a server-rendering integration.)
pub fn provide_meta_context() {
if use_context::<MetaContext>().is_none() {
provide_context(MetaContext::new());
}
}
/// Returns the current [`MetaContext`].
///
/// If there is no [`MetaContext`] in this or any parent scope, this will
/// create a new [`MetaContext`] and provide it to the current scope.
///
/// Note that this may cause confusing behavior, e.g., if multiple nested routes independently
/// call `use_head()` but a single [`MetaContext`] has not been provided at the application root.
/// The best practice is always to call [`provide_meta_context`] early in the application.
pub fn use_head() -> MetaContext {
#[cfg(debug_assertions)]
feature_warning();
match use_context::<MetaContext>() {
None => {
debug_warn!(
"use_head() is being called without a MetaContext being \
provided. We'll automatically create and provide one, but if \
this is being called in a child route it may cause bugs. To \
be safe, you should provide_meta_context() somewhere in the \
root of the app."
);
let meta = MetaContext::new();
provide_context(meta.clone());
meta
}
Some(ctx) => ctx,
}
}
impl MetaContext {
/// Creates an empty [`MetaContext`].
pub fn new() -> Self {
Default::default()
}
#[cfg(feature = "ssr")]
/// Converts the existing metadata tags into HTML that can be injected into the document head.
///
/// This should be called *after* the app’s component tree has been rendered into HTML, so that
/// components can set meta tags.
///
/// ```
/// use leptos::*;
/// use leptos_meta::*;
///
/// # #[cfg(not(any(feature = "csr", feature = "hydrate")))] {
/// # let runtime = create_runtime();
/// provide_meta_context();
///
/// let app = view! {
/// <main>
/// <Title text="my title"/>
/// <Stylesheet href="/style.css"/>
/// <p>"Some text"</p>
/// </main>
/// };
///
/// // `app` contains only the body content w/ hydration stuff, not the meta tags
/// assert!(
/// !app.into_view().render_to_string().contains("my title")
/// );
/// // `MetaContext::dehydrate()` gives you HTML that should be in the `<head>`
/// assert!(use_head().dehydrate().contains("<title>my title</title>"));
/// # runtime.dispose();
/// # }
/// ```
pub fn dehydrate(&self) -> String {
use leptos::leptos_dom::HydrationCtx;
let prev_key = HydrationCtx::peek();
let mut tags = String::new();
// Title
if let Some(title) = self.title.as_string() {
tags.push_str("<title>");
tags.push_str(&title);
tags.push_str("</title>");
}
tags.push_str(&self.tags.as_string());
if let Some(prev_key) = prev_key {
HydrationCtx::continue_from(prev_key);
}
tags
}
}
/// Extracts the metadata that should be used to close the `<head>` tag
/// and open the `<body>` tag. This is a helper function used in implementing
/// server-side HTML rendering across crates.
#[cfg(feature = "ssr")]
pub fn generate_head_metadata() -> String {
let (head, body) = generate_head_metadata_separated();
format!("{head}</head>{body}")
}
/// Extracts the metadata that should be inserted at the beginning of the `<head>` tag
/// and on the opening `<body>` tag. This is a helper function used in implementing
/// server-side HTML rendering across crates.
#[cfg(feature = "ssr")]
pub fn generate_head_metadata_separated() -> (String, String) {
let meta = use_context::<MetaContext>();
let head = meta
.as_ref()
.map(|meta| meta.dehydrate())
.unwrap_or_default();
let body_meta = meta
.as_ref()
.and_then(|meta| meta.body.as_string())
.unwrap_or_default();
(head, format!("<body{body_meta}>"))
}
#[cfg(debug_assertions)]
pub(crate) fn feature_warning() {
if !cfg!(any(feature = "csr", feature = "hydrate", feature = "ssr")) {
leptos::logging::debug_warn!("WARNING: `leptos_meta` does nothing unless you enable one of its features (`csr`, `hydrate`, or `ssr`). See the docs at https://docs.rs/leptos_meta/latest/leptos_meta/ for more information.");
}
}