Keyboard doesn't work in REPL

Lily · May 26, 2024, 2:08am

Keystrokes work only sporadically in the scala REPL (a key works sometimes, other times not). Windows 11. Scala 3.4.2. Java Version 8 update 411. I am new to scala.

spamegg1 · May 26, 2024, 6:34am

Welcome to the Scala community.
Is your keyboard working OK? Can you try a different keyboard?
Is your command line working OK? Can you try a different Terminal? Powershell maybe? (I don’t know much about Windows)
You should update your Java version to at least 11.

Quafadas · May 26, 2024, 7:06am

Are you launching via Scala-cli? Or Scala directly?

I would recommend trying scala-cli… Scala-cli will shortly become the Scala command …

Lily · May 26, 2024, 12:12pm

scala-cli works! Problem solved.

Many sincere thanks for your quick and helpful reply

spamegg1 · May 26, 2024, 12:19pm

It might be because Scala-cli uses a newer JVM. I think it requires 17, and downloads it if it’s not present.

If you start running into other issues outside the REPL, then try newer JVM versions.

Lily · May 26, 2024, 3:59pm

Thanks!

som-snytt · May 26, 2024, 5:32pm

For the record, Scala 3.4.2 has JLine 3.25.1 since this commit and Scala 2.13.14 since this commit.

“I don’t have a Windows 11 box to test on,” but I see there is a current ticket that is Windows-specific and says “missing keystrokes” in the title. There is no diagnosis or precise reproduction, but maybe some combination of factors causes a problem.

github.com/jline/jline3

Missing keystrokes when using System.console().readLine()

opened 01:23PM - 13 Mar 24 UTC

rehand

Hello, I've the problem that when using System.console().readLine() is used at …least twice in a row, starting with the second input/line always the first character is lost resp. read from the shell. I've created a patch for Repl.java of the demo project to reproduce the issue. When I'm doing two readLines and always type "test", the output is as follows: ``` JLine terminal: windows-vtp groovy-repl> testkey Input the first event: test Input the second event (here the first character is lost): est "testest" groovy-repl> t ``` Originally I thought it's an issue of picocli, so I created a [similar bug](https://github.com/remkop/picocli/issues/2222) there but it seems to be an issue of jline3. The issue affects only Windows, on Linux it works without problems. Also when using WSL2 works, so maybe it's an issue in combination with powershell and cmd. [readline.patch](https://github.com/jline/jline3/files/14588168/readline.patch)

Since the solution here was to use scala-cli, I guess this problem used scala at a command line prompt and not from the sbt prompt. In any case, the other item to verify is that the correct jline.jar and related jna.jar are getting used.

There was a previous issue with JDK 8 support in JLine that is not relevant here, but just goes to show that you can’t take anything for granted. Probably “don’t use JDK 8 any more” is good advice for those just starting out. I don’t know if there is any reason not to “use JDK 21 by default”.

spamegg1 · May 26, 2024, 6:35pm

Liques · June 16, 2024, 8:26pm

I had the same issue using Windows 11. The problem was related to the JDK version because I installed the latest one available now (version 22), now I downgraded it to the version 21 and it worked fine.

Blind88 · August 7, 2024, 3:28pm

Ahh this is probably my issue. I’m using 22 as well, but I’m going to try Scala-cli first. Also, I’m going through the introduction to Scala pages and it says you can use “Scala3” but I’m getting the “not recognized as cmdlet”. This is all in Powershell on Windows 10.

E: Scala-cli works nicely.