Streams2 Readable API confusion

[kanongil]

In general I like the new Readable API, but I think there is an issue with the use of the 'readable' event.

Currently consumers are encouraged to read() data synchronously when the event is signaled, however this means that any other listeners will have a different state depending on whether they are called before or after the one with the read(). Ie. if a listener is scheduled after the one doing read(), it will likely no longer be in a readable state.

I'm not sure what the correct solution is. A quick fix is to limit the 'readable' event to only one listener, but I'm not sure this is appropriate.

Another related issue, is how 'readable' interacts with pipe() and unpipe(), which is different depending on the order. Ie.

r.pipe(w);
r.on('readable', fn);

is not the same as

r.on('readable', fn);
r.pipe(w);

None of these work, as I would expect. I would expect that 'readable' is only called once there are no more pipes on the stream, and it hasn't yet ended, and has more data.

[indutny]

Are you, in general, trying to read from stream simultaneously with another reader?

[kanongil]

@indutny No, I'm not.

[isaacs]

The 'readable' event is a part of how pipe() works, so what you're asking for isn't really possible.

If you read() from a stream that is flowing through a pipe chain, then you'll probably mess stuff up. This is the same as any other unix stream in that way. You CAN pipe to multiple writers, so if you really need to be able to consume the bytes without screwing up the flow, you can do var myCopy = new stream.PassThrough(); src.pipe(myCopy); myCopy.on('readable', etc)