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

[Aaron Scott-Boddendijk]

I see that the release candidate didn't wait for this. JShell is completely
unusable without this fix for these users.

--
Aaron Scott-Boddendijk

On Sat, Feb 16, 2019 at 9:05 AM Robert Field <robert.field at oracle.com>
wrote:

> Thumbs up!
>
> This is important to fix.  Getting it in the JDK for full shake-out
> would be good.
>
> Per our discussion, let's try to find someone who can test multibyte
> encodings on Windows, with this in.
>
> -Robert
>
>
> On 2/13/19 6:45 AM, Jan Lahoda wrote:
> > 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
>