RFR: JDK-8218287: jshell tool: input behavior unstable after 12-ea+24 on Windows

[Jan Lahoda]

Hi,

When JShell was upgraded to use JLine 3.9.0, the input from which the 
Terminal is reading had to be wrapped, so that JShell can detect Ctrl-C 
while the user's code is running. The mechanism for this is that the 
StopDetectingInputStream is actively reading the input to find out if 
Ctrl-C was pressed. (And other characters are stored aside and returned 
from the StopDetectingInputStream when JLine is reading from it.)

Unfortunately, it turns out this wrapping is not done as expected on 
Windows (when using the Windows terminal). The issue is that the source 
of input in the AbstractWindowsTerminal is a Reader, which is directly 
used to read the input by JLine, and is also converted to an 
InputStream, which is typically not used. And this InputStream is 
wrapped by the StopDetectingInputStream. So when the 
StopDetectingInputStream is trying to detect Ctrl-C, it may "steal" an 
input character, which is then missing in the Reader used by JLine, and 
hence is lost (the StopDetectingInputStream has it stored aside, but it 
is never read from it).

The proposed patch is to not use the Reader that is the source of input 
directly, but rather create a new one based on the wrapped InputStream.

Webrev: http://cr.openjdk.java.net/~jlahoda/8218287/webrev.00/
JBS: https://bugs.openjdk.java.net/browse/JDK-8218287

How does this look?

Thanks,
     Jan