perf(neglible): completely veto Arc from AppState

Cargo.toml

@@ -43,6 +43,8 @@ multiple_crate_versions = { level = "allow" } # otherwise there's too much
 
 correctness = { level = "deny", priority = -1 }
 nursery = { level = "deny", priority = -1 }
+option_if_let_else = { level = "allow" } # I personally sometimes prefer what this prevents
+
 pedantic = { level = "deny", priority = -1 }
 perf = { level = "deny", priority = -1 }
 style = { level = "deny", priority = -1 }

src/server/mod.rs

@@ -4,6 +4,7 @@ use actix_web::{App, HttpServer, web};
 
 pub mod caches;
 pub mod services;
+pub mod static_app_data;
 
 pub struct AppState {
     pub args: crate::args::Args,
@@ -11,6 +12,9 @@ pub struct AppState {
     pub cache: caches::AppCache<'static>,
 }
 
+/// Type alias to be used just as `data: AppData,` extractor in [`actix_web`] request handlers.
+pub type AppData = static_app_data::StaticAppDataExtractor<&'static AppState>;
+
 /// Leaks memory for the sake of not atomic'ing all over.
 #[expect(clippy::missing_errors_doc)]
 pub async fn start_app(args: crate::args::Args, config: crate::conf::Config) -> io::Result<()> {
@@ -18,10 +22,7 @@ pub async fn start_app(args: crate::args::Args, config: crate::conf::Config) ->
 
     let config = Box::leak(Box::new(config));
 
-    let cache = caches::AppCache::new(
+    let cache = caches::AppCache::new(&config.unix.magic_paths, &config.unix.groups);
-        &config.unix.magic_paths,
-        &config.unix.groups,
-    );
 
     let app: &AppState = Box::leak(Box::new(AppState {
         args,
@@ -36,7 +37,7 @@ pub async fn start_app(args: crate::args::Args, config: crate::conf::Config) ->
 
     HttpServer::new(move || {
         App::new()
-            .app_data(web::Data::new(app))
+            .app_data(app)
             .service(services::images::make_scope(ws::IMAGES))
             .default_service(web::to(services::not_found::not_found))
     })

src/server/services/images.rs

@@ -15,7 +15,7 @@ use actix_web::{
 
 use crate::{
     consts::{self, web_scopes as ws},
-    server,
+    server::{self, AppData},
 };
 
 #[must_use]
@@ -27,7 +27,7 @@ pub fn make_scope(path: &str) -> actix_web::Scope {
 
 #[get("/")]
 async fn get_default_image(
-    _data: web::Data<&server::AppState>,
+    data: AppData,
     _username: web::Path<String>,
 ) -> HttpResponse {
     HttpResponse::Ok()
@@ -41,7 +41,7 @@ async fn get_default_image(
 
 #[get("/{username}")]
 async fn get_image(
-    data: web::Data<&server::AppState>,
+    data: AppData,
     username: web::Path<String>,
 ) -> web::Either<Redirect, HttpResponse> {
     let cached_pfp = data.cache.get_pfp(username.to_string()).await;

src/server/static_app_data.rs

@@ -0,0 +1,38 @@
+use std::{future::Ready, ops::Deref};
+
+use actix_web::{error::InternalError, http::StatusCode};
+
+/// App data extractor without any [`Arc`] inbetween, perefct if the app data is a simple
+/// `&'static` reference that can be copied, no atomic anywhere.
+pub struct StaticAppDataExtractor<T> {
+    pub data: T,
+}
+
+impl<T> Deref for StaticAppDataExtractor<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.data
+    }
+}
+
+impl<T: Copy + 'static> actix_web::FromRequest for StaticAppDataExtractor<T> {
+    type Error = InternalError<&'static str>;
+    type Future = Ready<Result<Self, Self::Error>>;
+
+    fn from_request(
+        req: &actix_web::HttpRequest,
+        _payload: &mut actix_web::dev::Payload,
+    ) -> Self::Future {
+        let val = match req.app_data::<T>() {
+            Some(&data) => Ok(Self { data }),
+            None => Err(InternalError::new(
+                "Requested application data is not configured correctly. \
+                View/enable debug logs for more details.",
+                StatusCode::INTERNAL_SERVER_ERROR,
+            )),
+        };
+
+        std::future::ready(val)
+    }
+}