rocket_dyn_templates/metadata.rs
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use std::fmt;
use std::borrow::Cow;
use rocket::{Request, Rocket, Ignite, Sentinel};
use rocket::http::{Status, ContentType};
use rocket::request::{self, FromRequest};
use rocket::serde::Serialize;
use crate::{Template, context::ContextManager};
/// Request guard for dynamically querying template metadata.
///
/// # Usage
///
/// The `Metadata` type implements Rocket's [`FromRequest`] trait, so it can be
/// used as a request guard in any request handler.
///
/// ```rust
/// # #[macro_use] extern crate rocket;
/// # #[macro_use] extern crate rocket_dyn_templates;
/// use rocket_dyn_templates::{Template, Metadata, context};
///
/// #[get("/")]
/// fn homepage(metadata: Metadata) -> Template {
/// // Conditionally render a template if it's available.
/// # let context = ();
/// if metadata.contains_template("some-template") {
/// Template::render("some-template", &context)
/// } else {
/// Template::render("fallback", &context)
/// }
/// }
///
/// fn main() {
/// rocket::build()
/// .attach(Template::fairing())
/// // ...
/// # ;
/// }
/// ```
pub struct Metadata<'a>(&'a ContextManager);
impl Metadata<'_> {
/// Returns `true` if the template with the given `name` is currently
/// loaded. Otherwise, returns `false`.
///
/// # Example
///
/// ```rust
/// # #[macro_use] extern crate rocket;
/// # extern crate rocket_dyn_templates;
/// #
/// use rocket_dyn_templates::Metadata;
///
/// #[get("/")]
/// fn handler(metadata: Metadata) {
/// // Returns `true` if the template with name `"name"` was loaded.
/// let loaded = metadata.contains_template("name");
/// }
/// ```
pub fn contains_template(&self, name: &str) -> bool {
self.0.context().templates.contains_key(name)
}
/// Returns `true` if template reloading is enabled.
///
/// # Example
///
/// ```rust
/// # #[macro_use] extern crate rocket;
/// # extern crate rocket_dyn_templates;
/// #
/// use rocket_dyn_templates::Metadata;
///
/// #[get("/")]
/// fn handler(metadata: Metadata) {
/// // Returns `true` if template reloading is enabled.
/// let reloading = metadata.reloading();
/// }
/// ```
pub fn reloading(&self) -> bool {
self.0.is_reloading()
}
/// Directly render the template named `name` with the context `context`
/// into a `String`. Also returns the template's detected `ContentType`. See
/// [`Template::render()`] for more details on rendering.
///
/// # Examples
///
/// ```rust
/// # #[macro_use] extern crate rocket;
/// use rocket::http::ContentType;
/// use rocket_dyn_templates::{Metadata, Template, context};
///
/// #[get("/")]
/// fn send_email(metadata: Metadata) -> Option<()> {
/// let (mime, string) = metadata.render("email", context! {
/// field: "Hello, world!"
/// })?;
///
/// # /*
/// send_email(mime, string).await?;
/// # */
/// Some(())
/// }
///
/// #[get("/")]
/// fn raw_render(metadata: Metadata) -> Option<(ContentType, String)> {
/// metadata.render("index", context! { field: "Hello, world!" })
/// }
///
/// // Prefer the following, however, which is nearly identical but pithier:
///
/// #[get("/")]
/// fn render() -> Template {
/// Template::render("index", context! { field: "Hello, world!" })
/// }
/// ```
pub fn render<S, C>(&self, name: S, context: C) -> Option<(ContentType, String)>
where S: Into<Cow<'static, str>>, C: Serialize
{
Template::render(name.into(), context).finalize(&self.0.context()).ok()
}
}
impl fmt::Debug for Metadata<'_> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_map()
.entries(&self.0.context().templates)
.finish()
}
}
impl Sentinel for Metadata<'_> {
fn abort(rocket: &Rocket<Ignite>) -> bool {
if rocket.state::<ContextManager>().is_none() {
error!(
"uninitialized template context: missing `Template::fairing()`.\n\
To use templates, you must attach `Template::fairing()`."
);
return true;
}
false
}
}
/// Retrieves the template metadata. If a template fairing hasn't been attached,
/// an error is printed and an empty `Err` with status `InternalServerError`
/// (`500`) is returned.
#[rocket::async_trait]
impl<'r> FromRequest<'r> for Metadata<'r> {
type Error = ();
async fn from_request(request: &'r Request<'_>) -> request::Outcome<Self, ()> {
request.rocket().state::<ContextManager>()
.map(|cm| request::Outcome::Success(Metadata(cm)))
.unwrap_or_else(|| {
error!(
"uninitialized template context: missing `Template::fairing()`.\n\
To use templates, you must attach `Template::fairing()`."
);
request::Outcome::Error((Status::InternalServerError, ()))
})
}
}