Add space between SSE field and value for compatibility (#2149)

Co-authored-by: David Pedersen <david.pdrsn@gmail.com>

axum/CHANGELOG.md

@@ -64,6 +64,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **change:** axum's MSRV is now 1.63 ([#2021])
 - **added:** Implement `Handler` for `T: IntoResponse` ([#2140])
 - **added:** Implement `IntoResponse` for `(R,) where R: IntoResponse` ([#2143])
+- **changed:** For SSE, add space between field and value for compatibility ([#2149])
 
 [#2021]: https://github.com/tokio-rs/axum/pull/2021
 [#2014]: https://github.com/tokio-rs/axum/pull/2014
@@ -82,6 +83,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 [#2096]: https://github.com/tokio-rs/axum/pull/2096
 [#2140]: https://github.com/tokio-rs/axum/pull/2140
 [#2143]: https://github.com/tokio-rs/axum/pull/2143
+[#2149]: https://github.com/tokio-rs/axum/pull/2149
 
 # 0.6.17 (25. April, 2023)
 

axum/src/response/sse.rs

@@ -171,9 +171,9 @@ pub struct Event {
 }
 
 impl Event {
- /// Set the event's data data field(s) (`data:<content>`)
+ /// Set the event's data data field(s) (`data: <content>`)
  ///
- /// Newlines in `data` will automatically be broken across `data:` fields.
+ /// Newlines in `data` will automatically be broken across `data: ` fields.
  ///
  /// This corresponds to [`MessageEvent`'s data field].
  ///
@@ -202,7 +202,7 @@ impl Event {
  self
  }
 
- /// Set the event's data field to a value serialized as unformatted JSON (`data:<content>`).
+ /// Set the event's data field to a value serialized as unformatted JSON (`data: <content>`).
  ///
  /// This corresponds to [`MessageEvent`'s data field].
  ///
@@ -220,7 +220,7 @@ impl Event {
  panic!("Called `EventBuilder::json_data` multiple times");
  }
 
- self.buffer.extend_from_slice(b"data:");
+ self.buffer.extend_from_slice(b"data: ");
  serde_json::to_writer((&mut self.buffer).writer(), &data).map_err(axum_core::Error::new)?;
  self.buffer.put_u8(b'\n');
 
@@ -358,10 +358,7 @@ impl Event {
  );
  self.buffer.extend_from_slice(name.as_bytes());
  self.buffer.put_u8(b':');
- // Prevent values that start with spaces having that space stripped
- if value.starts_with(b" ") {
- self.buffer.put_u8(b' ');
- }
+ self.buffer.put_u8(b' ');
  self.buffer.extend_from_slice(value);
  self.buffer.put_u8(b'\n');
  }
@@ -532,7 +529,7 @@ mod tests {
  #[test]
  fn leading_space_is_not_stripped() {
  let no_leading_space = Event::default().data("\tfoobar");
- assert_eq!(&*no_leading_space.finalize(), b"data:\tfoobar\n\n");
+ assert_eq!(&*no_leading_space.finalize(), b"data: \tfoobar\n\n");
 
  let leading_space = Event::default().data(" foobar");
  assert_eq!(&*leading_space.finalize(), b"data: foobar\n\n");