From 2308f8afa4b71dad726d5a3534e7eb4b1469098a Mon Sep 17 00:00:00 2001
From: Rob Ede <robjtede@icloud.com>
Date: Mon, 27 Dec 2021 16:15:20 +0000
Subject: [PATCH] use const header values where possible

---
 actix-http/src/h2/dispatcher.rs                  |  8 +++++---
 actix-http/src/header/shared/content_encoding.rs |  4 ++--
 actix-http/src/ws/mod.rs                         |  5 +++--
 awc/src/client/h2proto.rs                        |  8 +++++---
 awc/src/ws.rs                                    | 13 ++++++++-----
 src/middleware/default_headers.rs                |  7 +++----
 6 files changed, 26 insertions(+), 19 deletions(-)

diff --git a/actix-http/src/h2/dispatcher.rs b/actix-http/src/h2/dispatcher.rs
index 7f0f15ee..a90eb346 100644
--- a/actix-http/src/h2/dispatcher.rs
+++ b/actix-http/src/h2/dispatcher.rs
@@ -288,9 +288,11 @@ fn prepare_response(
     let _ = match size {
         BodySize::None | BodySize::Stream => None,
 
-        BodySize::Sized(0) => res
-            .headers_mut()
-            .insert(CONTENT_LENGTH, HeaderValue::from_static("0")),
+        BodySize::Sized(0) => {
+            #[allow(clippy::declare_interior_mutable_const)]
+            const HV_ZERO: HeaderValue = HeaderValue::from_static("0");
+            res.headers_mut().insert(CONTENT_LENGTH, HV_ZERO)
+        }
 
         BodySize::Sized(len) => {
             let mut buf = itoa::Buffer::new();
diff --git a/actix-http/src/header/shared/content_encoding.rs b/actix-http/src/header/shared/content_encoding.rs
index a6e52138..68511a8e 100644
--- a/actix-http/src/header/shared/content_encoding.rs
+++ b/actix-http/src/header/shared/content_encoding.rs
@@ -45,13 +45,13 @@ pub enum ContentEncoding {
 impl ContentEncoding {
     /// Is the content compressed?
     #[inline]
-    pub fn is_compression(self) -> bool {
+    pub const fn is_compression(self) -> bool {
         matches!(self, ContentEncoding::Identity | ContentEncoding::Auto)
     }
 
     /// Convert content encoding to string.
     #[inline]
-    pub fn as_str(self) -> &'static str {
+    pub const fn as_str(self) -> &'static str {
         match self {
             ContentEncoding::Br => "br",
             ContentEncoding::Gzip => "gzip",
diff --git a/actix-http/src/ws/mod.rs b/actix-http/src/ws/mod.rs
index 6491da14..568d801a 100644
--- a/actix-http/src/ws/mod.rs
+++ b/actix-http/src/ws/mod.rs
@@ -99,8 +99,9 @@ impl From<HandshakeError> for Response<BoxBody> {
         match err {
             HandshakeError::GetMethodRequired => {
                 let mut res = Response::new(StatusCode::METHOD_NOT_ALLOWED);
-                res.headers_mut()
-                    .insert(header::ALLOW, HeaderValue::from_static("GET"));
+                #[allow(clippy::declare_interior_mutable_const)]
+                const HV_GET: HeaderValue = HeaderValue::from_static("GET");
+                res.headers_mut().insert(header::ALLOW, HV_GET);
                 res
             }
 
diff --git a/awc/src/client/h2proto.rs b/awc/src/client/h2proto.rs
index 9ced5776..709896dd 100644
--- a/awc/src/client/h2proto.rs
+++ b/awc/src/client/h2proto.rs
@@ -52,9 +52,11 @@ where
     let _ = match length {
         BodySize::None => None,
 
-        BodySize::Sized(0) => req
-            .headers_mut()
-            .insert(CONTENT_LENGTH, HeaderValue::from_static("0")),
+        BodySize::Sized(0) => {
+            #[allow(clippy::declare_interior_mutable_const)]
+            const HV_ZERO: HeaderValue = HeaderValue::from_static("0");
+            req.headers_mut().insert(CONTENT_LENGTH, HV_ZERO)
+        }
 
         BodySize::Sized(len) => {
             let mut buf = itoa::Buffer::new();
diff --git a/awc/src/ws.rs b/awc/src/ws.rs
index 96f8cf89..f3ee02d4 100644
--- a/awc/src/ws.rs
+++ b/awc/src/ws.rs
@@ -300,13 +300,16 @@ impl WebsocketsRequest {
         }
 
         self.head.set_connection_type(ConnectionType::Upgrade);
+
+        #[allow(clippy::declare_interior_mutable_const)]
+        const HV_WEBSOCKET: HeaderValue = HeaderValue::from_static("websocket");
+        self.head.headers.insert(header::UPGRADE, HV_WEBSOCKET);
+
+        #[allow(clippy::declare_interior_mutable_const)]
+        const HV_THIRTEEN: HeaderValue = HeaderValue::from_static("13");
         self.head
             .headers
-            .insert(header::UPGRADE, HeaderValue::from_static("websocket"));
-        self.head.headers.insert(
-            header::SEC_WEBSOCKET_VERSION,
-            HeaderValue::from_static("13"),
-        );
+            .insert(header::SEC_WEBSOCKET_VERSION, HV_THIRTEEN);
 
         if let Some(protocols) = self.protocols.take() {
             self.head.headers.insert(
diff --git a/src/middleware/default_headers.rs b/src/middleware/default_headers.rs
index 89210b15..003abd40 100644
--- a/src/middleware/default_headers.rs
+++ b/src/middleware/default_headers.rs
@@ -100,10 +100,9 @@ impl DefaultHeaders {
     ///
     /// Default is `application/octet-stream`.
     pub fn add_content_type(self) -> Self {
-        self.add((
-            CONTENT_TYPE,
-            HeaderValue::from_static("application/octet-stream"),
-        ))
+        #[allow(clippy::declare_interior_mutable_const)]
+        const HV_MIME: HeaderValue = HeaderValue::from_static("application/octet-stream");
+        self.add((CONTENT_TYPE, HV_MIME))
     }
 }