Panic when sending a message

[Nikolai Zimmermann]

I am trying to send DuckerZ as einarmwischer in #fischklatscher but get a panic.

my code:

let cmd = commands::privmsg(channel, &msg);
dbg!(cmd);
writer.encode(cmd).await?;

dbg! returns:

[src/bot.rs:42] cmd = Privmsg {
    channel: "fischklatscher",
    msg: "DuckerZ",
}

log snippet:

[tbc::bot] TRACE Sending message to fischklatscher
[src/bot.rs:42] cmd = Privmsg {
    channel: "fischklatscher",
    msg: "DuckerZ",
}
[twitchchat::decoder] TRACE < :einarmwischer.tmi.twitch.tv 353 einarmwischer = #fischklatscher :einarmwischer\r\n
[twitchchat::runner::async_runner] TRACE < :einarmwischer.tmi.twitch.tv 353 einarmwischer = #fischklatscher :einarmwischer\r\n
[twitchchat::runner::async_runner] TRACE draining messages
[twitchchat::decoder] TRACE < :einarmwischer.tmi.twitch.tv 366 einarmwischer #fischklatscher :End of /NAMES list\r\n
[twitchchat::runner::async_runner] TRACE < :einarmwischer.tmi.twitch.tv 366 einarmwischer #fischklatscher :End of /NAMES list\r\n
[twitchchat::runner::async_runner] TRACE draining messages
[twitchchat::runner::rate_limit] TRACE > PRIVMSG #fischklatscher :DuckerZ\r\n

Panic occurs at:

twitchchat/src/runner/async_runner.rs

Lines 323 to 324 in 0a58541

 let msg = crate::irc::IrcMessage::parse(crate::MaybeOwned::Borrowed(msg)) 
     .expect("encoder should produce valid IRC messages"); 

[Nikolai Zimmermann]

I tried reproducing the panic but the code in this gist did not panic

[museun]

That is odd, the stuff in commands (e.g. privmsg()) should always produce messages that the internal stuff can parse.

for example:

let msg = "DuckerZ";
let channel = "fischklatscher";
let cmd = commands::privmsg(channel, &msg);

let mut v = vec![];
cmd.encode(&mut v).unwrap();

let msg = std::str::from_utf8(&v).unwrap();
eprintln!("{}", msg.escape_debug());
// PRIVMSG #fischklatscher :DuckerZ\r\n

let msg = IrcMessage::parse(msg.into()).unwrap();
eprintln!("{:#?}", msg);
// IrcMessage {
//     raw: "PRIVMSG #fischklatscher :DuckerZ\r\n",
//     tags: None,
//     prefix: None,
//     command: "PRIVMSG",
//     args: Some(
//         "#fischklatscher",
//     ),
//     data: Some(
//         "DuckerZ",
//     ),
// }

Are you sure thats where the panic was?

[Nikolai Zimmermann]

This is the log line I get

thread 'async-std/runtime' panicked at 'encoder should produce valid IRC messages: EmptyMessage', /home/chrono/.cargo/registry/src/github.com-1ecc6299db9ec823/twitchchat-0.12.2/src/runner/async_runner.rs:323:27

[museun]

Currently IrcMessage::parse can only fail in one way: if the string is empty

twitchchat/src/irc/message.rs

Lines 31 to 34 in 0a58541

 let data = data.trim(); 
 if data.is_empty() { 
     return Err(super::MessageError::EmptyMessage); 
 } 

And privmsg() et.al ensure the string isn't empty (it always includes a \r\n). (The trim is the above example is working on a subslice so the \r\n doesn't get trimmed.).

Were you manually writing and not using the Encodable interface?

[Nikolai Zimmermann]

As I wrote above I am using AsyncWriter::encode and passing Privmsg. I get the writer from AsyncRunner::writer.

[museun]

Also, as a note, in your gist the 'encode' will not block on the send -- so you need to wait for a bit before ending the test. You may or may not actually do a write because the test ends before the enqueue/rate_limit machinery can do its stuff.

I've tried both with empty messages and empty channels and I cannot get it to fail on the parse.

With the AsyncRunner -- next_message() actually de-queues any possble/pending rate-limited messages and does the writing. The part that is failing is where it reads from the raw user input and determines whether a message should be considered for rate limiting or not. Each channel has its own rate limit (including things like 'slow-mode').

[Nikolai Zimmermann]

I see.

I know what I may have done wrong. Since you mentioned manually writing I checked my code again and also took a look at the AsyncEncoder::encode and noticed that flush gets called. I had a flush after sending every message.
Removing said call and the panic does not occur anymore.

[museun]

Oh! That is a bug, a flush on an MpscWriter doesn't actually check to see if any data was buffered.

twitchchat/src/writer/mpsc_writer.rs

Lines 58 to 76 in 0a58541

     fn flush(&mut self) -> io::Result<()> { 
         use crate::channel::TrySendError; 
  
         let buf = std::mem::take(&mut self.buf); 
         match self.channel.try_send(buf.into_boxed_slice()) { 
             Ok(..) => Ok(()), 
             Err(TrySendError::Closed(..)) => { 
                 let err = io::Error::new(io::ErrorKind::UnexpectedEof, "writer was closed"); 
                 Err(err) 
             } 
             // this should never happen, but place the 'data' back into self and 
             // have it try again 
             Err(TrySendError::Full(data)) => { 
                 self.buf = data.into(); 
                 Ok(()) 
             } 
         } 
     } 
 } 

[museun]

I fixed it in b9f362a

I'll publish a release later today, theres a few more things I want to change.

[museun]

I released the fix in 7f3f9ff