Allow users of picocli-shell-jline3 to use clear command and a nicer help command

picocli-shell-jline3/src/main/java/picocli/shell/jline3/PicocliCommands.java

@@ -1,7 +1,15 @@
 package picocli.shell.jline3;
 
+import java.io.IOException;
 import java.nio.file.Path;
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.Callable;
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
@@ -13,19 +21,18 @@
 import org.jline.reader.Completer;
 import org.jline.reader.LineReader;
 import org.jline.reader.ParsedLine;
+import org.jline.reader.impl.LineReaderImpl;
+import org.jline.reader.impl.completer.ArgumentCompleter;
+import org.jline.reader.impl.completer.NullCompleter;
 import org.jline.reader.impl.completer.SystemCompleter;
 import org.jline.utils.AttributedString;
+
 import picocli.CommandLine;
+import picocli.CommandLine.Command;
 import picocli.CommandLine.Help;
 import picocli.CommandLine.Model.CommandSpec;
 import picocli.CommandLine.Model.OptionSpec;
 
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
 /**
  * Compiles SystemCompleter for command completion and implements a method commandDescription() that provides command descriptions
  * for JLine TailTipWidgets to be displayed in terminal status bar.
@@ -35,6 +42,26 @@
  * @since 4.1.2
  */
 public class PicocliCommands implements CommandRegistry {
+
+    /**
+     * Command that clears the screen.
+     */
+    @Command(name = "cls", aliases = "clear", mixinStandardHelpOptions = true,
+            description = "Clears the screen", version = "1.0")
+    static class ClearScreen implements Callable<Void> {
+
+    	private final LineReaderImpl reader;
+
+        ClearScreen(LineReaderImpl reader) {
+			this.reader = reader;
+		}
+
+		public Void call() throws IOException {
+            reader.clearScreen();
+            return null;
+        }
+    }
+
     private final Supplier<Path> workDir;
     private final CommandLine cmd;
     private final Set<String> commands;
@@ -47,14 +74,25 @@ public PicocliCommands(Path workDir, CommandLine cmd) {
     public PicocliCommands(Supplier<Path> workDir, CommandLine cmd) {
         this.workDir = workDir;
         this.cmd = cmd;
-        commands = cmd.getCommandSpec().subcommands().keySet();
+        commands = new HashSet<>(cmd.getCommandSpec().subcommands().keySet());
         for (String c: commands) {
             for (String a: cmd.getSubcommands().get(c).getCommandSpec().aliases()) {
                 aliasCommand.put(a, c);
             }
         }
     }
 
+    public void includeClearScreenCommand(LineReader reader) {
+    	if (reader == null) return;
+    	ClearScreen clearScreen = new ClearScreen((LineReaderImpl) reader);
+    	cmd.addSubcommand(clearScreen);
+
+    	commands.add("clear");
+
+    	aliasCommand.put("clear", "clear");
+    	aliasCommand.put("cls", "clear");
+    }
+
     /**
      *
      * @param command
@@ -74,9 +112,9 @@ public SystemCompleter compileCompleters() {
         return out;
     }
 
-    private class PicocliCompleter implements Completer {
+    private class PicocliCompleter extends ArgumentCompleter implements Completer {
 
-        public PicocliCompleter() {}
+        public PicocliCompleter() { super(NullCompleter.INSTANCE); }
 
         @Override
         public void complete(LineReader reader, ParsedLine commandLine, List<Candidate> candidates) {

picocli-shell-jline3/src/test/java/picocli/shell/jline3/example/Example.java

@@ -42,18 +42,12 @@ public class Example {
                     ""},
             footer = {"", "Press Ctl-D to exit."},
             subcommands = {
-                    MyCommand.class, ClearScreen.class, CommandLine.HelpCommand.class})
+                    MyCommand.class, CommandLine.HelpCommand.class})
     static class CliCommands implements Runnable {
-        LineReaderImpl reader;
         PrintWriter out;
 
         CliCommands() {}
 
-        public void setReader(LineReader reader){
-            this.reader = (LineReaderImpl)reader;
-            out = reader.getTerminal().writer();
-        }
-
         public void run() {
             out.println(new CommandLine(this).getUsageMessage());
         }
@@ -128,21 +122,6 @@ public void subtract(@Option(names = {"-l", "--left"}, required = true) int left
         }
     }
 
-    /**
-     * Command that clears the screen.
-     */
-    @Command(name = "cls", aliases = "clear", mixinStandardHelpOptions = true,
-            description = "Clears the screen", version = "1.0")
-    static class ClearScreen implements Callable<Void> {
-
-        @ParentCommand CliCommands parent;
-
-        public Void call() throws IOException {
-            parent.reader.clearScreen();
-            return null;
-        }
-    }
-
     private static Path workDir() {
         return Paths.get(System.getProperty("user.dir"));
     }
@@ -164,6 +143,7 @@ public static void main(String[] args) {
             try (Terminal terminal = TerminalBuilder.builder().build()) {
                 SystemRegistry systemRegistry = new SystemRegistryImpl(parser, terminal, Example::workDir, null);
                 systemRegistry.setCommandRegistries(builtins, picocliCommands);
+                systemRegistry.register("help", picocliCommands);
 
                 LineReader reader = LineReaderBuilder.builder()
                         .terminal(terminal)
@@ -172,7 +152,7 @@ public static void main(String[] args) {
                         .variable(LineReader.LIST_MAX, 50)   // max tab completion candidates
                         .build();
                 builtins.setLineReader(reader);
-                commands.setReader(reader);
+                picocliCommands.includeClearScreenCommand(reader);
                 TailTipWidgets widgets = new TailTipWidgets(reader, systemRegistry::commandDescription, 5, TailTipWidgets.TipType.COMPLETER);
                 widgets.enable();
                 KeyMap<Binding> keyMap = reader.getKeyMaps().get("main");