From 1fe04cf51e6f907d91db1abd91e4808958f79d0d Mon Sep 17 00:00:00 2001
From: Rob Ede <robjtede@icloud.com>
Date: Sun, 16 Jan 2022 02:35:10 +0000
Subject: [PATCH] allow camel case response headers

closes #1979
---
 actix-http/CHANGES.md            |  4 ++
 actix-http/Cargo.toml            |  1 +
 actix-http/src/h1/encoder.rs     |  6 +++
 actix-http/src/responses/head.rs | 68 +++++++++++++++++++++++++++++++-
 4 files changed, 78 insertions(+), 1 deletion(-)

diff --git a/actix-http/CHANGES.md b/actix-http/CHANGES.md
index a58846405..d03a45969 100644
--- a/actix-http/CHANGES.md
+++ b/actix-http/CHANGES.md
@@ -1,10 +1,14 @@
 # Changes
 
 ## Unreleased - 2021-xx-xx
+### Added
+- Response headers can be sent as camel case using `res.head_mut().set_camel_case_headers(true)`. [#2587]
+
 ### Changed
 - Brotli (de)compression support is now provided by the `brotli` crate. [#2538]
 
 [#2538]: https://github.com/actix/actix-web/pull/2538
+[#2587]: https://github.com/actix/actix-web/pull/2587
 
 
 ## 3.0.0-beta.18 - 2022-01-04
diff --git a/actix-http/Cargo.toml b/actix-http/Cargo.toml
index df9e11419..163fce931 100644
--- a/actix-http/Cargo.toml
+++ b/actix-http/Cargo.toml
@@ -88,6 +88,7 @@ async-stream = "0.3"
 criterion = { version = "0.3", features = ["html_reports"] }
 env_logger = "0.9"
 futures-util = { version = "0.3.7", default-features = false, features = ["alloc"] }
+memchr = "2.4"
 rcgen = "0.8"
 regex = "1.3"
 rustls-pemfile = "0.2"
diff --git a/actix-http/src/h1/encoder.rs b/actix-http/src/h1/encoder.rs
index f2a862278..8b1e3b623 100644
--- a/actix-http/src/h1/encoder.rs
+++ b/actix-http/src/h1/encoder.rs
@@ -258,6 +258,12 @@ impl MessageType for Response<()> {
         None
     }
 
+    fn camel_case(&self) -> bool {
+        self.head()
+            .flags
+            .contains(crate::message::Flags::CAMEL_CASE)
+    }
+
     fn encode_status(&mut self, dst: &mut BytesMut) -> io::Result<()> {
         let head = self.head();
         let reason = head.reason().as_bytes();
diff --git a/actix-http/src/responses/head.rs b/actix-http/src/responses/head.rs
index 78d9536e5..d11ba8fde 100644
--- a/actix-http/src/responses/head.rs
+++ b/actix-http/src/responses/head.rs
@@ -20,7 +20,7 @@ pub struct ResponseHead {
     pub headers: HeaderMap,
     pub reason: Option<&'static str>,
     pub(crate) extensions: RefCell<Extensions>,
-    flags: Flags,
+    pub(crate) flags: Flags,
 }
 
 impl ResponseHead {
@@ -49,6 +49,18 @@ impl ResponseHead {
         &mut self.headers
     }
 
+    /// Sets the flag that controls wether to send headers formatted as Camel-Case.
+    ///
+    /// Only applicable to HTTP/1.x responses; HTTP/2 header names are always lowercase.
+    #[inline]
+    pub fn set_camel_case_headers(&mut self, camel_case: bool) {
+        if camel_case {
+            self.flags.insert(Flags::CAMEL_CASE);
+        } else {
+            self.flags.remove(Flags::CAMEL_CASE);
+        }
+    }
+
     /// Message extensions
     #[inline]
     pub fn extensions(&self) -> Ref<'_, Extensions> {
@@ -206,3 +218,57 @@ impl BoxedResponsePool {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::{
+        io::{Read as _, Write as _},
+        net,
+    };
+
+    use memchr::memmem;
+
+    use crate::{
+        header::{HeaderName, HeaderValue},
+        Error, HttpService, Request, Response,
+    };
+
+    #[actix_rt::test]
+    async fn camel_case_headers() {
+        let mut srv = actix_http_test::test_server(|| {
+            HttpService::new(|req: Request| async move {
+                let mut res = Response::ok();
+
+                if req.path().contains("camel") {
+                    res.head_mut().set_camel_case_headers(true);
+                }
+
+                res.headers_mut().insert(
+                    HeaderName::from_static("foo-bar"),
+                    HeaderValue::from_static("baz"),
+                );
+                Ok::<_, Error>(res)
+            })
+            .tcp()
+        })
+        .await;
+
+        let mut stream = net::TcpStream::connect(srv.addr()).unwrap();
+        let _ = stream.write_all(b"GET /camel HTTP/1.1\r\nConnection: Close\r\n\r\n");
+        let mut data = vec![0; 1024];
+        let _ = stream.read(&mut data);
+        assert_eq!(&data[..17], b"HTTP/1.1 200 OK\r\n");
+        assert!(memmem::find(&data, b"Foo-Bar").is_some());
+        assert!(!memmem::find(&data, b"foo-bar").is_some());
+
+        let mut stream = net::TcpStream::connect(srv.addr()).unwrap();
+        let _ = stream.write_all(b"GET /lower HTTP/1.1\r\nConnection: Close\r\n\r\n");
+        let mut data = vec![0; 1024];
+        let _ = stream.read(&mut data);
+        assert_eq!(&data[..17], b"HTTP/1.1 200 OK\r\n");
+        assert!(!memmem::find(&data, b"Foo-Bar").is_some());
+        assert!(memmem::find(&data, b"foo-bar").is_some());
+
+        srv.stop().await;
+    }
+}