sse-stream

Breaking API changes

• Encoding: TryFrom<Sse> for Bytes replaces From<Sse> for Bytes. Replace Bytes::from(event) or event.into() with event.encode()? or Bytes::try_from(event)?.
• Keep-alive events: KeepAlive::event returns Result<KeepAlive, EncodeError>. Use KeepAlive::new().event(event)?.
• Body errors: SseBody::Error is now BodyError, not the input error E. Match BodyError::Stream for boxed upstream errors and BodyError::Encode for encoding errors; upstream error sources are preserved.
• Input error bounds: SseBody requires E: Into<Box<dyn std::error::Error + Send + Sync>>.
• Error matching: Removed InvalidLine, DuplicatedEventLine, DuplicatedIdLine, DuplicatedRetry, and IntParse. Error, EncodeError, and BodyError are non-exhaustive; add wildcard arms.
• Decoder constructor: Removed from_byte_stream, deprecated since 0.2.4. Use SseByteStream::new or the retained SseStream::from_bytes_stream.
• Decoder auto traits: SseStream<B> now also requires B::Data: Send or Sync to implement the corresponding trait, since it retains input buffers. Standard Bytes buffers are unaffected.
• Body construction: Struct literals are no longer supported. Use SseBody::new(stream) or SseBody::new_keep_alive(stream, config).
• Keep-alive access: SseBody::keep_alive is private. Use has_keep_alive() to inspect it and with_keep_alive() to configure it. Directly clearing the configuration is no longer supported.

Behavior changes

• Terminal errors: Decoders and SseBody emit an error once, then end. Keep-alives stop too. To resume decoding, create a decoder for a new input stream.
• Unknown fields: Ignored by default instead of rejected; colonless fields have empty values. The opt-in strict-fields feature rejects unknown names with the always-public Error::UnknownField unit variant, emitted once before termination. Cargo feature unification applies this policy to all users of the same resolved crate.
• Repeated metadata: event, id, and retry use the last valid value.
• Retry parsing: Only ASCII digits fitting in u64 are accepted. Empty, signed, padded, or overflowing values are ignored without replacing a valid value.
• Ignored text: Comments are ignored regardless of encoding or tracing settings. Unknown fields are also ignored regardless of encoding unless strict-fields is enabled; strict mode rejects unknown names without validating their UTF-8.
• Metadata validation: Encoding rejects CR/LF in event types and CR/LF/NULL in ids, including direct field assignments. No bytes are returned on failure.
• Multiline data: Every line receives a data: prefix. Empty and trailing lines are preserved; CRLF and bare CR are normalized to LF.
• Keep-alive comments: Every line receives a comment prefix, preventing field injection.
• Retry duration: retry_duration saturates at u64::MAX milliseconds instead of wrapping.

Clarified existing behavior

• Sse represents raw blocks, including metadata-only blocks. Fields are not inherited; connection and reconnection state belongs to the caller.
• Recognized field values require valid UTF-8; ids containing NULL are ignored.
• Incomplete final blocks are discarded at EOF.

Structure and performance

• Both decoders implement FusedStream and release parser buffers on error or EOF.
• Added default memchr and simdutf8 features for line scanning and long-field UTF-8 validation, with standard-library fallbacks when disabled.
• HTTP body decoding delegates to the byte-stream decoder, sharing polling and error lifecycle handling. Parser states, data buffering, scanning, encoding, errors, and keep-alive scheduling have dedicated modules.
• New lines have separate comment, data, and empty-boundary paths. Empty lines dispatch directly; complete data lines followed by LF/LF finish the event in the same iteration. Fragmented data values append directly to the data buffer.
• After a data event or buffered line completes, each parser scratch buffer retains at most 64 KiB. This bounds retained scratch capacity, not the size of an in-progress event or the caller's input/output buffers.
• Added feature-matrix CI and targeted coverage for terminal errors, field rules, multiline encoding, wake-ups, and keep-alive resets.
• Published crate contents exclude benchmark experiment archives and tooling files. Benchmarks and regression tests remain included.