Make command not found configurable

- New CommandNotFoundResultHandler which handles
  CommandNotFound to be able to customize error shown.
- New CommandNotFoundMessageProvider which is a plain
  function given a "context" and returns a string.
  Context contains common info to provide better
  error messages.
- Default provider gives same message but
  removes long stacktrace(which previously originated
  from a common ThrowableResultHandler.
- Relates #778

spring-shell-core/src/main/java/org/springframework/shell/CommandNotFound.java

@@ -1,6 +1,5 @@
 /*
- * Copyright 2017 the original author or authors.
- *
+ * Copyright 2017-2023
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
@@ -18,17 +17,28 @@ package org.springframework.shell;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
 import java.util.stream.Collectors;
 
+import org.springframework.shell.command.CommandRegistration;
+
 /**
  * A result to be handled by the {@link ResultHandler} when no command could be mapped to user input
  */
 public class CommandNotFound extends RuntimeException {
 
 	private final List<String> words;
+	private final Map<String, CommandRegistration> registrations;
+	private final String text;
 
 	public CommandNotFound(List<String> words) {
+		this(words, null, null);
+	}
+
+	public CommandNotFound(List<String> words, Map<String, CommandRegistration> registrations, String text) {
 		this.words = words;
+		this.registrations = registrations;
+		this.text = text;
 	}
 
 	@Override
@@ -44,4 +54,22 @@ public class CommandNotFound extends RuntimeException {
 	public List<String> getWords(){
 		return new ArrayList<>(words);
 	}
+
+	/**
+	 * Gets command registrations known when this error was created.
+	 *
+	 * @return known command registrations
+	 */
+	public Map<String, CommandRegistration> getRegistrations() {
+		return registrations;
+	}
+
+	/**
+	 * Gets a raw text input.
+	 *
+	 * @return raw text input
+	 */
+	public String getText() {
+		return text;
+	}
 }

spring-shell-core/src/main/java/org/springframework/shell/Shell.java

@@ -18,6 +18,7 @@ package org.springframework.shell;
 import java.lang.reflect.UndeclaredThrowableException;
 import java.nio.channels.ClosedByInterruptException;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -201,13 +202,14 @@ public class Shell {
 		String line = words.stream().collect(Collectors.joining(" ")).trim();
 		String command = findLongestCommand(line, false);
 
+		Map<String, CommandRegistration> registrations = commandRegistry.getRegistrations();
 		if (command == null) {
-			return new CommandNotFound(words);
+			return new CommandNotFound(words, new HashMap<>(registrations), input.rawText());
 		}
 
 		log.debug("Evaluate input with line=[{}], command=[{}]", line, command);
 
-		Optional<CommandRegistration> commandRegistration = commandRegistry.getRegistrations().values().stream()
+		Optional<CommandRegistration> commandRegistration = registrations.values().stream()
 			.filter(r -> {
 				if (r.getCommand().equals(command)) {
 					return true;
@@ -222,7 +224,7 @@ public class Shell {
 			.findFirst();
 
 		if (commandRegistration.isEmpty()) {
-			return new CommandNotFound(words);
+			return new CommandNotFound(words, new HashMap<>(registrations), input.rawText());
 		}
 
 		if (this.exitCodeMappings != null) {

spring-shell-core/src/main/java/org/springframework/shell/result/CommandNotFoundMessageProvider.java

@@ -0,0 +1,92 @@
+/*
+ * Copyright 2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.shell.result;
+
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+
+import org.springframework.shell.command.CommandRegistration;
+import org.springframework.shell.result.CommandNotFoundMessageProvider.ProviderContext;
+
+/**
+ * Provider for a message used within {@link CommandNotFoundResultHandler}.
+ *
+ * @author Janne Valkealahti
+ */
+@FunctionalInterface
+public interface CommandNotFoundMessageProvider extends Function<ProviderContext, String> {
+
+	static ProviderContext contextOf(Throwable error, List<String> commands, Map<String, CommandRegistration> registrations, String text) {
+		return new ProviderContext() {
+
+			@Override
+			public Throwable error() {
+				return error;
+			}
+
+			@Override
+			public List<String> commands() {
+				return commands;
+			}
+
+			@Override
+			public Map<String, CommandRegistration> registrations() {
+				return registrations;
+			}
+
+			@Override
+			public String text() {
+				return text;
+			}
+		};
+	}
+
+	/**
+	 * Context for {@link CommandNotFoundResultHandler}.
+	 */
+	interface ProviderContext {
+
+		/**
+		 * Gets an actual error.
+		 *
+		 * @return actual error
+		 */
+		Throwable error();
+
+		/**
+		 * Gets a list of commands parsed.
+		 *
+		 * @return list of commands parsed
+		 */
+		List<String> commands();
+
+		/**
+		 * Gets a command registrations.
+		 *
+		 * @return a command registrations
+		 */
+		Map<String, CommandRegistration> registrations();
+
+		/**
+		 * Gets a raw input text.
+		 *
+		 * @return a raw input text
+		 */
+		String text();
+	}
+
+}

spring-shell-core/src/main/java/org/springframework/shell/result/CommandNotFoundResultHandler.java

@@ -0,0 +1,52 @@
+package org.springframework.shell.result;
+
+import org.jline.terminal.Terminal;
+import org.jline.utils.AttributedString;
+import org.jline.utils.AttributedStyle;
+
+import org.springframework.beans.factory.ObjectProvider;
+import org.springframework.shell.CommandNotFound;
+import org.springframework.shell.ResultHandler;
+import org.springframework.shell.result.CommandNotFoundMessageProvider.ProviderContext;
+import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
+
+/**
+ * {@link ResultHandler} for {@link CommandNotFound} using
+ * {@link CommandNotFoundMessageProvider} to provide an error message.
+ * Default internal provider simply provides message from a {@link CommandNotFound}
+ * with a red color. Provider can be defined by providing a custom
+ * {@link CommandNotFoundMessageProvider} bean.
+ *
+ * @author Janne Valkealahti
+ */
+public final class CommandNotFoundResultHandler extends TerminalAwareResultHandler<CommandNotFound> {
+
+	private CommandNotFoundMessageProvider provider;
+
+	public CommandNotFoundResultHandler(Terminal terminal, ObjectProvider<CommandNotFoundMessageProvider> provider) {
+		super(terminal);
+		Assert.notNull(provider, "provider cannot be null");
+		this.provider = provider.getIfAvailable(() -> new DefaultProvider());
+	}
+
+	@Override
+	protected void doHandleResult(CommandNotFound result) {
+		ProviderContext context = CommandNotFoundMessageProvider.contextOf(result, result.getWords(),
+				result.getRegistrations(), result.getText());
+		String message = provider.apply(context);
+		if (StringUtils.hasText(message)) {
+			terminal.writer().println(message);
+		}
+	}
+
+	private static class DefaultProvider implements CommandNotFoundMessageProvider {
+
+		@Override
+		public String apply(ProviderContext context) {
+			String message = new AttributedString(context.error().getMessage(),
+					AttributedStyle.DEFAULT.foreground(AttributedStyle.RED)).toAnsi();
+			return message;
+		}
+	}
+}

spring-shell-core/src/main/java/org/springframework/shell/result/ResultHandlerConfig.java

@@ -70,4 +70,10 @@ public class ResultHandlerConfig {
 			ShellContext shellContext, ObjectProvider<InteractiveShellRunner> interactiveApplicationRunner) {
 		return new ThrowableResultHandler(terminal, commandCatalog, shellContext, interactiveApplicationRunner);
 	}
+
+	@Bean
+	public CommandNotFoundResultHandler commandNotFoundResultHandler(Terminal terminal,
+		ObjectProvider<CommandNotFoundMessageProvider> provider) {
+		return new CommandNotFoundResultHandler(terminal, provider);
+	}
 }