From 2bfd51372e0f62981226ccc86e4ad46e586a788b Mon Sep 17 00:00:00 2001
From: Jonas Platte <jplatte@users.noreply.github.com>
Date: Wed, 17 Nov 2021 20:53:07 +0100
Subject: [PATCH] Use named constants for static header values (#535)

Improves performance by moving some computation to compile time.
---
 axum/Cargo.toml          |  2 +-
 axum/src/json.rs         |  9 +++++----
 axum/src/response/mod.rs | 39 +++++++++++++++++++--------------------
 3 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/axum/Cargo.toml b/axum/Cargo.toml
index 011ef0b3..890c0ed8 100644
--- a/axum/Cargo.toml
+++ b/axum/Cargo.toml
@@ -25,7 +25,7 @@ async-trait = "0.1.43"
 bitflags = "1.0"
 bytes = "1.0"
 futures-util = { version = "0.3", default-features = false, features = ["alloc"] }
-http = "0.2"
+http = "0.2.5"
 http-body = "0.4.4"
 hyper = { version = "0.14.14", features = ["server", "tcp", "stream"] }
 matchit = "0.4.4"
diff --git a/axum/src/json.rs b/axum/src/json.rs
index 75b9a589..e3534301 100644
--- a/axum/src/json.rs
+++ b/axum/src/json.rs
@@ -176,6 +176,9 @@ where
     type BodyError = Infallible;
 
     fn into_response(self) -> Response<Self::Body> {
+        #[allow(clippy::declare_interior_mutable_const)]
+        const APPLICATION_JSON: HeaderValue = HeaderValue::from_static("application/json");
+
         let bytes = match serde_json::to_vec(&self.0) {
             Ok(res) => res,
             Err(err) => {
@@ -188,10 +191,8 @@ where
         };
 
         let mut res = Response::new(Full::from(bytes));
-        res.headers_mut().insert(
-            header::CONTENT_TYPE,
-            HeaderValue::from_static("application/json"),
-        );
+        res.headers_mut()
+            .insert(header::CONTENT_TYPE, APPLICATION_JSON);
         res
     }
 }
diff --git a/axum/src/response/mod.rs b/axum/src/response/mod.rs
index b87139ff..b51a77aa 100644
--- a/axum/src/response/mod.rs
+++ b/axum/src/response/mod.rs
@@ -331,23 +331,26 @@ impl IntoResponse for std::borrow::Cow<'static, str> {
     type BodyError = Infallible;
 
     fn into_response(self) -> Response<Self::Body> {
+        #[allow(clippy::declare_interior_mutable_const)]
+        const TEXT_PLAIN: HeaderValue = HeaderValue::from_static("text/plain");
+
         let mut res = Response::new(Full::from(self));
-        res.headers_mut()
-            .insert(header::CONTENT_TYPE, HeaderValue::from_static("text/plain"));
+        res.headers_mut().insert(header::CONTENT_TYPE, TEXT_PLAIN);
         res
     }
 }
 
+#[allow(clippy::declare_interior_mutable_const)]
+const APPLICATION_OCTET_STREAM: HeaderValue = HeaderValue::from_static("application/octet-stream");
+
 impl IntoResponse for Bytes {
     type Body = Full<Bytes>;
     type BodyError = Infallible;
 
     fn into_response(self) -> Response<Self::Body> {
         let mut res = Response::new(Full::from(self));
-        res.headers_mut().insert(
-            header::CONTENT_TYPE,
-            HeaderValue::from_static("application/octet-stream"),
-        );
+        res.headers_mut()
+            .insert(header::CONTENT_TYPE, APPLICATION_OCTET_STREAM);
         res
     }
 }
@@ -358,10 +361,8 @@ impl IntoResponse for &'static [u8] {
 
     fn into_response(self) -> Response<Self::Body> {
         let mut res = Response::new(Full::from(self));
-        res.headers_mut().insert(
-            header::CONTENT_TYPE,
-            HeaderValue::from_static("application/octet-stream"),
-        );
+        res.headers_mut()
+            .insert(header::CONTENT_TYPE, APPLICATION_OCTET_STREAM);
         res
     }
 }
@@ -372,10 +373,8 @@ impl IntoResponse for Vec<u8> {
 
     fn into_response(self) -> Response<Self::Body> {
         let mut res = Response::new(Full::from(self));
-        res.headers_mut().insert(
-            header::CONTENT_TYPE,
-            HeaderValue::from_static("application/octet-stream"),
-        );
+        res.headers_mut()
+            .insert(header::CONTENT_TYPE, APPLICATION_OCTET_STREAM);
         res
     }
 }
@@ -386,10 +385,8 @@ impl IntoResponse for std::borrow::Cow<'static, [u8]> {
 
     fn into_response(self) -> Response<Self::Body> {
         let mut res = Response::new(Full::from(self));
-        res.headers_mut().insert(
-            header::CONTENT_TYPE,
-            HeaderValue::from_static("application/octet-stream"),
-        );
+        res.headers_mut()
+            .insert(header::CONTENT_TYPE, APPLICATION_OCTET_STREAM);
         res
     }
 }
@@ -471,9 +468,11 @@ where
     type BodyError = Infallible;
 
     fn into_response(self) -> Response<Self::Body> {
+        #[allow(clippy::declare_interior_mutable_const)]
+        const TEXT_HTML: HeaderValue = HeaderValue::from_static("text/html");
+
         let mut res = Response::new(self.0.into());
-        res.headers_mut()
-            .insert(header::CONTENT_TYPE, HeaderValue::from_static("text/html"));
+        res.headers_mut().insert(header::CONTENT_TYPE, TEXT_HTML);
         res
     }
 }