Support sending events without an event: field for the event name

The event field is optional in the specification, and adds overhead,
which some applications do not want. Allow omitting it.

To simplify use, accept the name as `impl Into<Option<&str>>`, which
allows existing code that passes `"name"` to continue working. Since
this can potentially cause an inference failure in code that previously
compiled, bump the major version, but *most* code should continue
working with just a recompile.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "async-sse"
-version = "4.1.0"
+version = "5.0.0"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/http-rs/async-sse"
 documentation = "https://docs.rs/async-sse"

src/encoder.rs

@@ -100,10 +100,16 @@ impl Sender {
     }
 
     /// Send a new message over SSE.
-    pub async fn send(&self, name: &str, data: &str, id: Option<&str>) -> io::Result<()> {
+    pub async fn send(
+        &self,
+        name: impl Into<Option<&str>>,
+        data: &str,
+        id: Option<&str>,
+    ) -> io::Result<()> {
         // Write the event name
-        let msg = format!("event:{}\n", name);
-        self.inner_send(msg).await?;
+        if let Some(name) = name.into() {
+            self.inner_send(format!("event:{}\n", name)).await?;
+        }
 
         // Write the id
         if let Some(id) = id {

tests/encode.rs

@@ -37,6 +37,28 @@ async fn encode_message() -> http_types::Result<()> {
     Ok(())
 }
 
+#[async_std::test]
+async fn encode_message_some() -> http_types::Result<()> {
+    let (sender, encoder) = encode();
+    task::spawn(async move { sender.send(Some("cat"), "chashu", None).await });
+
+    let mut reader = decode(BufReader::new(encoder));
+    let event = reader.next().await.unwrap()?;
+    assert_message(&event, "cat", "chashu", None);
+    Ok(())
+}
+
+#[async_std::test]
+async fn encode_message_data_only() -> http_types::Result<()> {
+    let (sender, encoder) = encode();
+    task::spawn(async move { sender.send(None, "chashu", None).await });
+
+    let mut reader = decode(BufReader::new(encoder));
+    let event = reader.next().await.unwrap()?;
+    assert_message(&event, "message", "chashu", None);
+    Ok(())
+}
+
 #[async_std::test]
 async fn encode_message_with_id() -> http_types::Result<()> {
     let (sender, encoder) = encode();
@@ -48,6 +70,17 @@ async fn encode_message_with_id() -> http_types::Result<()> {
     Ok(())
 }
 
+#[async_std::test]
+async fn encode_message_data_only_with_id() -> http_types::Result<()> {
+    let (sender, encoder) = encode();
+    task::spawn(async move { sender.send(None, "chashu", Some("0")).await });
+
+    let mut reader = decode(BufReader::new(encoder));
+    let event = reader.next().await.unwrap()?;
+    assert_message(&event, "message", "chashu", Some("0"));
+    Ok(())
+}
+
 #[async_std::test]
 async fn encode_retry() -> http_types::Result<()> {
     let (sender, encoder) = encode();