Add unicode handling capability

[lenianiva]

Previously, if the client program outputs unicode, the unicode output would be garbled when it is piped through NBReader. For more detail, see #105. Writing doesn't seem to have any trouble as demonstrated by examples/cat.rs.

Right now the unicode encoder is always on. In pexpect, an encoding option is available to toggle between the two, which I'm not sure where to put here.

[lenianiva]

The current behaviour is to withhold a half-completed unicode char from the output buffer. If the client program outputs EOF when the unicode char buffer is incomplete, the char is swallowed. However one problem is that if the client program outputs an invalid unicode char and then valid unicode chars, the output buffer will be stalled and no more chars will be piped into the buffer.

[matthiasbeyer]

Thanks for your patches and also for your bug report! :heart: Highly appreciated!

The CI failure should be fixed after #107 is merged, don't worry about that.

I am not sure what the way forward is yet. I like the first option you proposed in #105 most:

Change the type of PipedChar(u8) to PipedChar(char): If the program sends over half of a unicode char and then stop it would hang the reader

But that might break some downstream users for non-UTF8 outputting programs, as I understand it!? @petreeftime maybe you have some ideas what's the best way to go here? Maybe make the whole thing configurable (a flag that can be passed to the library for each call)?

[lenianiva]

Thanks for your patches and also for your bug report! ❤️ Highly appreciated!

The CI failure should be fixed after #107 is merged, don't worry about that.

I am not sure what the way forward is yet. I like the first option you proposed in #105 most:

Change the type of PipedChar(u8) to PipedChar(char): If the program sends over half of a unicode char and then stop it would hang the reader

But that might break some downstream users for non-UTF8 outputting programs, as I understand it!? @petreeftime maybe you have some ideas what's the best way to go here? Maybe make the whole thing configurable (a flag that can be passed to the library for each call)?

I don't think the first option is the best one. The solution in this PR is kind of a compromise between the first two options. This is because the underlying datatype piped by the client program is always u8 and not some char type, and any assembly of u8 into chars is only really needed when downstream needs to check the existence of certain chars to e.g. break line or search a regex.

TLDR: Unicode encoding necessarily runs the risk of stalling the buffer, and this happens either in the read thread or the write thread.

You're correct that this may break non-UTF8 outputting programs, but if the program restricts its output to the ASCII range there shouldn't be any compatibility issue. I left a flag in the code to represent some external option which toggles between unicode and non-unicode encoding.

Do you think it would be sensible to add it as a crate-level feature? Or embed the option in every instance of NBReader and hence spawn (this is the solution from pexpect)?

[matthiasbeyer]

If anything I'd have it as an option on the data type, not a crate-level feature or compiletime option, because of the simple fact that someone might have UTF-8 outputting programs and non-UTF-8 outputting programs in one project. In general I think compiletime features should never be used for "either-or" functionality :laughing:

So a flag on the type would be totally fine with me, with UTF-8 compatible reading as the default.

I'd like to see what @petreeftime thinks as well though.

[lenianiva]

If anything I'd have it as an option on the data type, not a crate-level feature or compiletime option, because of the simple fact that someone might have UTF-8 outputting programs and non-UTF-8 outputting programs in one project. In general I think compiletime features should never be used for "either-or" functionality 😆

So a flag on the type would be totally fine with me, with UTF-8 compatible reading as the default.

I'd like to see what @petreeftime thinks as well though.

If you have any idea for where to add such a flag I can do it in this PR.

By the way why is Pull Request Checks failing? Is it because I didn't sign my commits?

[matthiasbeyer]

By the way why is Pull Request Checks failing? Is it because I didn't sign my commits?

Its because you didn't signoff your commits (the -s flag in git-commit). You can fix this by doing something like git rebase $(git merge-base origin/master HEAD) -x "git commit --amend --no-edit -s" (there might be a more elegant way... :shrug:)

[matthiasbeyer]

We merged #107 that should make your compile issues go away, please do rebase to latest master.

[lenianiva]

We merged #107 that should make your compile issues go away, please do rebase to latest master.

Rebased. I added a field for NBReader which contains the encoding. The encoding cannot be set via a setter because by the time the setter is called the receiving thread may have already received one or two chars, so the encoding has to be known by the time NBReader::new is called. Whether you would like this function argument to NBReader::new to be rippled to everything else that uses NBReader::new is your call.

I think the problem about the client program stalling the buffer should not be an issue that needs handling. If the client program outputs a invalid unicode char followed by valid unicode then it is not outputting unicode anyways so UTF8 mode is inadequate.

[lenianiva]

Overall this looks good.

I think having the encoding be an argument on new, but also providing two convenience helpers NBReader::ascii() and NBReader::utf8(), which call new with the respective argument would be nice and not that much of a hassle.

@petreeftime pinging you again, hope you can have a look as well.

Have you decided that this is the way to go? I need this crate in production

[lenianiva]

I've merged master into this branch and propagated encoding into the new Options structure. By default it still uses ASCII encoding everywhere. However I'm getting this error:

---- session::tests::test_bash stdout ----
thread 'session::tests::test_bash' panicked at 'assertion failed: `(left == right)`
  left: `"/tmp\r\n"`,
 right: `"\u{1b}[?2004l\r\r\n/tmp\r\n\u{1b}[?2004h"`', src/session.rs:543:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

it seems like bash is generating some extra outputs? This also occurs on the master branch.