8308591: JLine as the default Console provider

Reviewed-by: alanb

src/java.base/share/classes/java/io/Console.java

@@ -344,16 +344,33 @@ public sealed class Console implements Flushable permits ProxyingConsole {
         throw newUnsupportedOperationException();
     }
 
+    /**
+     * {@return {@code true} if the {@code Console} instance is a terminal}
+     * <p>
+     * This method returns {@code true} if the console device, associated with the current
+     * Java virtual machine, is a terminal, typically an interactive command line
+     * connected to a keyboard and display.
+     *
+     * @implNote The default implementation returns the value equivalent to calling
+     * {@code isatty(stdin/stdout)} on POSIX platforms, or whether standard in/out file
+     * descriptors are character devices or not on Windows.
+     *
+     * @since 22
+     */
+    public boolean isTerminal() {
+        return istty;
+    }
+
     private static UnsupportedOperationException newUnsupportedOperationException() {
         return new UnsupportedOperationException(
                 "Console class itself does not provide implementation");
     }
 
     private static native String encoding();
+    private static final boolean istty = istty();
     static final Charset CHARSET;
     static {
         Charset cs = null;
-        boolean istty = istty();
 
         if (istty) {
             String csname = encoding();

src/java.base/share/classes/java/io/ProxyingConsole.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -34,17 +34,13 @@ import jdk.internal.io.JdkConsole;
  */
 final class ProxyingConsole extends Console {
     private final JdkConsole delegate;
-    private final Object readLock;
+    private final Object readLock = new Object();
-    private final Object writeLock;
+    private final Object writeLock = new Object();
-    private final Reader reader;
+    private volatile Reader reader;
-    private final PrintWriter printWriter;
+    private volatile PrintWriter printWriter;
 
     ProxyingConsole(JdkConsole delegate) {
         this.delegate = delegate;
-        readLock = new Object();
-        writeLock = new Object();
-        reader = new WrappingReader(delegate.reader(), readLock);
-        printWriter = new WrappingWriter(delegate.writer(), writeLock);
     }
 
     /**
@@ -52,6 +48,16 @@ final class ProxyingConsole extends Console {
      */
     @Override
     public PrintWriter writer() {
+        PrintWriter printWriter = this.printWriter;
+        if (printWriter == null) {
+            synchronized (this) {
+                printWriter = this.printWriter;
+                if (printWriter == null) {
+                    printWriter = new WrappingWriter(delegate.writer(), writeLock);
+                    this.printWriter = printWriter;
+                }
+            }
+        }
         return printWriter;
     }
 
@@ -60,6 +66,16 @@ final class ProxyingConsole extends Console {
      */
     @Override
     public Reader reader() {
+        Reader reader = this.reader;
+        if (reader == null) {
+            synchronized (this) {
+                reader = this.reader;
+                if (reader == null) {
+                    reader = new WrappingReader(delegate.reader(), readLock);
+                    this.reader = reader;
+                }
+            }
+        }
         return reader;
     }
 

src/java.base/share/classes/jdk/internal/io/JdkConsoleProvider.java

@@ -33,7 +33,7 @@ public interface JdkConsoleProvider {
     /**
      * The module name of the JdkConsole default provider.
      */
-    String DEFAULT_PROVIDER_MODULE_NAME = "java.base";
+    String DEFAULT_PROVIDER_MODULE_NAME = "jdk.internal.le";
 
     /**
      * {@return the Console instance, or {@code null} if not available}

src/jdk.internal.le/share/classes/jdk/internal/org/jline/JdkConsoleProviderImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -91,6 +91,7 @@ public class JdkConsoleProviderImpl implements JdkConsoleProvider {
         @Override
         public String readLine(String fmt, Object ... args) {
             try {
+                initJLineIfNeeded();
                 return jline.readLine(fmt.formatted(args));
             } catch (EndOfFileException eofe) {
                 return null;
@@ -105,6 +106,7 @@ public class JdkConsoleProviderImpl implements JdkConsoleProvider {
         @Override
         public char[] readPassword(String fmt, Object ... args) {
             try {
+                initJLineIfNeeded();
                 return jline.readLine(fmt.formatted(args), '\0').toCharArray();
             } catch (EndOfFileException eofe) {
                 return null;
@@ -126,12 +128,24 @@ public class JdkConsoleProviderImpl implements JdkConsoleProvider {
             return terminal.encoding();
         }
 
-        private final LineReader jline;
         private final Terminal terminal;
+        private volatile LineReader jline;
 
         public JdkConsoleImpl(Terminal terminal) {
             this.terminal = terminal;
-            this.jline = LineReaderBuilder.builder().terminal(terminal).build();
+        }
+
+        private void initJLineIfNeeded() {
+            LineReader jline = this.jline;
+            if (jline == null) {
+                synchronized (this) {
+                    jline = this.jline;
+                    if (jline == null) {
+                        jline = LineReaderBuilder.builder().terminal(terminal).build();
+                        this.jline = jline;
+                    }
+                }
+            }
         }
     }
 }

test/jdk/java/io/Console/ModuleSelectionTest.java

@@ -27,7 +27,7 @@
  * @summary Tests System.console() returns correct Console (or null) from the expected
  *          module.
  * @modules java.base/java.io:+open
- * @run main/othervm ModuleSelectionTest java.base
+ * @run main/othervm ModuleSelectionTest jdk.internal.le
  * @run main/othervm -Djdk.console=jdk.internal.le ModuleSelectionTest jdk.internal.le
  * @run main/othervm -Djdk.console=java.base ModuleSelectionTest java.base
  * @run main/othervm --limit-modules java.base ModuleSelectionTest java.base