Re: [streams] Clarify how/whether Stream/TransformStream may read/write "messages" (#249)

(Sorry for the delay in the response.)

> to clarify if the stream API may be used to send/receive atomic messages, in addition to byte-arrays. 

Ah! That is indeed explicitly supported: https://streams.spec.whatwg.org/#chunk

> Response C-T is application/json. The server is streaming a list of "entities" as a JSON array to the client application. Then, could I install a custom or predefined Transform function so that each chunk as delivered by the Stream API will represent a valid JSON element (or any array of elements).

Yep, this is exactly the envisioned way for streams to work. You might get a raw byte stream representing the HTTP response body from fetch(), but then you could pipe it through a transform stream that transforms it into streams of JavaScript objects, one per each JSON object or similar. In code:

```js
var byteStream = fetch("https://example.com/newline-delimited-json").body;
var transform = new NewlineDelimitedJSONTransform();
var jsObjectStream = byteStream.pipeThrough(transform);
```

(An example of something similar to `NewlineDelimitedJSONTransform`, albeit for Node.js streams instead of the streams described in this spec, is https://github.com/maxogden/ndjson)

> 1.1 states that we should respect any wire-level message framing, as in the case of WebSocket.

Yeah, this is definitely the intent. The implementer of a (for-now hypothetical) WebSocketStream would use the framing information to determine what data to enqueue in the stream, or whether to enqueue an error or close the stream.

---
Reply to this email directly or view it on GitHub:
https://github.com/whatwg/streams/issues/249#issuecomment-66810921