External print

[gwenn]

See #229

cargo run --example external_print

To do:

• Windows platform (only one printer supported, and when the printer is dropped we still wait)
• Check interaction with history search, completion, ...

[gwenn]

https://github.com/ghc/ghc/blob/master/libraries/base/cbits/inputReady.c#L325

nightmare. A Console Handle will appear to be ready
...

[flxo]

I tried this branch and discovered the following: When using the printer from different threads, the blocking readline call somehow interferes with the std::io::Write implementation produced by create_external_printer.

On unix or windows ?

Sorry forgot to add this. I tested on a x86 Linux and Mac.

[gwenn]

I will try to have a look this week-end.

[gwenn]

@flxo Ok, we should not use a BufReader here. Because buffered lines are not "selectable" anymore...

[gwenn]

@flxo Your issue should have been fixed by 0a5f0a4 on unix platform.

[flxo]

@gwenn Thanks for the update. I tried your patches and the issue is gone.

In my software I have a (hacky) std::io::Write impl around the rustyline::ExternalPrinter which allows me to use std::io::stdout and the rustyline interface dependant on the use case (iteractive or not).
Would it be possible to provide std::io::Write directly?

[gwenn]

@gwenn Thanks for the update. I tried your patches and the issue is gone.

In my software I have a (hacky) std::io::Write impl around the rustyline::ExternalPrinter which allows me to use std::io::stdout and the rustyline interface dependant on the use case (iteractive or not).
Would it be possible to provide std::io::Write directly?

You should be able to implement an ExternalPrinter that writes to stdout, no ? Like here

[flxo]

@gwenn My idea is to do something like

impl<T> std::io::Write for T where T: ExternalPrinter {
   ...
}

The prints are some via the writeln! family and with the impl of std::io::Write I can decided whether to use std::io::Stdout for non interactive usage (there's no rustyline::Editor around) and the thing returned from create_external_printer

let out = if interactive {
  Box::new(rl.create_external_printer()?) as Box<dyn std::io::Write>
} else {
  Box::new(std::io::stdout()) as Box<dyn std::io::Write>
}

writeln!(out, "test");

[gwenn]

The ExternalPrinter is now message oriented (\n is not meaningful anymore).
And Write is bytes/stream oriented.
So I would prefer that you implements Write on your own ExternalPrinter wrapper.

[bartlomieju]

Is there any chance this PR could be landed? We use rustyline for REPL in Deno and this feature would greatly improve the experience for streaming output (denoland/deno#8049), currently the output is interleaved with prompt line.

EDIT: Actually not a huge priority, we're gonna experiment with different crate for this purpose https://docs.rs/reedline

[gwenn]

Is there any chance this PR could be landed?

Current implementation is incomplete on windows.

EDIT: Actually not a huge priority, we're gonna experiment with different crate for this purpose https://docs.rs/reedline

#579

[vi]

Current implementation is incomplete on windows.

Can UNIX-only implementation land first then?

Shall an updated, but limited scope pull request (with ExternalPrinter cfg-gated) be submitted?

[gwenn]

Could you please give it another try (windows implementation should be fine now) ?
Thanks.