kakoune: [BUG] JSON UI only shows stdin when connecting to an existing session

Version of Kakoune

v2021.11.08

Reproducer

Create a script that will print text without exiting:

# make_commands.sh
while :
do
    echo '{"jsonrpc":"2.0","method":"keys","params":["e"]}'
    sleep 1
done

Then, create a named kak session

kak -ui "json" -s "test"

Then, try to connect with a second client that has a non-tty stdin:

sh ./make_commands.sh | kak -ui "json" -c "test"

Outcome

the second client shows a FIFO buffer where the contents of stdin are displayed as text rather than interpreted as commands.

Expectations

If you pipe input into a normal kak instance, it will display the text from stdin in a fifo buffer.

sh ./make_commands.sh | kak 

(The status line shows *stdin* 1:1 [scratch][fifo] 1 sel - client0@[1608978].)

If you pipe text to stdin of a kak instance created with -ui json, it will know to treat the input as JSON RPC commands and open the normal scratch buffer.

sh ./make_commands.sh | kak -ui "json"

{ "jsonrpc": "2.0", "method": "draw_status", "params": [[], [{ "face": { "fg": "default", "bg": "default", "underline": "default", "attributes": [] }, "contents": "*scratch* 1:1 " }, { "face": { "fg": "black", "bg": "yellow", "underline": "default", "attributes": [] }, "contents": "[scratch]" }, { "face": { "fg": "default", "bg": "default", "underline": "default", "attributes": [] }, "contents": " " }, { "face": { "fg": "blue", "bg": "default", "underline": "default", "attributes": [] }, "contents": "1 sel" }, { "face": { "fg": "default", "bg": "default", "underline": "default", "attributes": [] }, "contents": " - client0@[1610796]" }], { "fg": "cyan", "bg": "default", "underline": "default", "attributes": [] }] }

But, if you pipe into the stdin of a JSON UI client that is connecting to an existing session, it goes back to the original behaviour where the input is interpreted as text, not commands, and is displayed (the status line is [fifo]).

sh ./make_commands.sh | kak -ui "json" -c "test"

{ "jsonrpc": "2.0", "method": "draw_status", "params": [[], [{ "face": { "fg": "default", "bg": "default", "underline": "default", "attributes": [] }, "contents": "*stdin-1* 1:1 " }, { "face": { "fg": "black", "bg": "yellow", "underline": "default", "attributes": [] }, "contents": "[scratch][fifo]" }, { "face": { "fg": "default", "bg": "default", "underline": "default", "attributes": [] }, "contents": " " }, { "face": { "fg": "blue", "bg": "default", "underline": "default", "attributes": [] }, "contents": "1 sel" }, { "face": { "fg": "default", "bg": "default", "underline": "default", "attributes": [] }, "contents": " - client1@[test]" }], { "fg": "cyan", "bg": "default", "underline": "default", "attributes": [] }] }

This makes multiple clients useless for JSON UI because you cannot interact with them by sending commands. Instead, it should interpret stdin as RPC commands and not display them to the user

Additional information

I am using Ubuntu 20.04.2 LTS.

I first encountered this error running kak from a Rust program with

Command::new("kak")
    .args(&["-ui", "json"])
    .args(&["-c", "test"])
    .stdout(Stdio::piped())
    .stdin(Stdio::piped())
    .spawn()
    .unwrap()

but I was able to reproduce it in the terminal (Alacritty) as well.

This error seems to be a regression. A very old version of kak (probably from a couple years ago – I don’t remember the version number) did not have this issue but a late 2020 or early 2021 version introduced it.