RFR: 8352693: Use a simpler console reader instead of JLine for System.console()

[Alan Bateman]

On Wed, 26 Mar 2025 07:54:48 GMT, Jan Lahoda <jlahoda at openjdk.org> wrote:

> The `java.io.Console` has several backends: a simple on in `java.base`, a more convenient one in `jdk.internal.le` (with line-reading based on JLine) and one for JShell.
> 
> The backend based on JLine is proving to be a somewhat problematic - JLine is very powerful, possibly too powerful and complex for the simple task of editing a line with no completion, no history, no variables, no commands, etc. As a consequence, there are inevitable sharp edges in this backend.
> 
> The idea in this PR is to replace the use of JLine in the `jdk.internal.le` backend with a simple escape code interpreter, that only handles a handful of keys/codes (left/right arrow, home, end, delete, backspace, enter), and ignores the rest. The goal is to have something simple with less surprising behavior.

Can you coordinate with Naoto on this? There is a CSR in progress to switch Console back to using the java.base implementation by default.

src/java.base/share/classes/module-info.java line 172:

> 170:         java.rmi,
> 171:         jdk.charsets,
> 172:         jdk.internal.le,

What code in JLine is using shared secrets? I wonder what we need to change to avoid this.

src/java.base/share/classes/module-info.java line 304:

> 302:     exports sun.nio.cs to
> 303:         jdk.charsets,
> 304:         jdk.internal.le;

Same thing here.

src/jdk.internal.le/share/classes/jdk/internal/console/SimpleConsoleReader.java line 51:

> 49:     }
> 50: 
> 51:     private static void doReadImpl(Reader reader, Writer out, boolean password, int firstLineOffset, IntSupplier terminalWidthSupplier, CleanableBuffer result) throws IOException {

These overly long lines make it really hard to see the changes going forward so I think trim back some of these to make it easy to look at diffs in the future.

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PR Comment: https://git.openjdk.org/jdk/pull/24242#issuecomment-2753642709
PR Review Comment: https://git.openjdk.org/jdk/pull/24242#discussion_r2013662676
PR Review Comment: https://git.openjdk.org/jdk/pull/24242#discussion_r2013664086
PR Review Comment: https://git.openjdk.org/jdk/pull/24242#discussion_r2013660028