Allow printing of the full stacktrace after an error

Fixes #70

spring-shell2-core/src/main/java/org/springframework/shell2/result/ThrowableResultHandler.java

@@ -17,8 +17,12 @@
 package org.springframework.shell2.result;
 
 import org.jline.utils.AttributedString;
+import org.jline.utils.AttributedStringBuilder;
 import org.jline.utils.AttributedStyle;
 
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Lazy;
+import org.springframework.shell2.CommandRegistry;
 import org.springframework.shell2.ResultHandler;
 import org.springframework.stereotype.Component;
 
@@ -30,9 +34,36 @@ import org.springframework.stereotype.Component;
 @Component
 public class ThrowableResultHandler extends TerminalAwareResultHandler implements ResultHandler<Throwable> {
 
+	/**
+	 * The name of the command that may be used to print details about the last error.
+	 */
+	public static final String DETAILS_COMMAND_NAME = "stacktrace";
+
+	private Throwable lastError;
+
+	@Autowired @Lazy
+	private CommandRegistry commandRegistry;
+
 	@Override
 	public void handleResult(Throwable result) {
+		lastError = result;
 		terminal.writer().println(new AttributedString(result.toString(),
 				AttributedStyle.DEFAULT.foreground(AttributedStyle.RED)).toAnsi());
+		if (commandRegistry.listCommands().containsKey(DETAILS_COMMAND_NAME)) {
+			terminal.writer().println(
+				new AttributedStringBuilder()
+					.append("Details of the error have been omitted. You can use the ", AttributedStyle.DEFAULT.foreground(AttributedStyle.RED))
+					.append(DETAILS_COMMAND_NAME, AttributedStyle.DEFAULT.foreground(AttributedStyle.RED).bold())
+					.append(" command to print the full stacktrace.", AttributedStyle.DEFAULT.foreground(AttributedStyle.RED))
+					.toAnsi()
+			);
+		}
+	}
+
+	/**
+	 * Return the last error that was dealt with by this result handler.
+	 */
+	public Throwable getLastError() {
+		return lastError;
 	}
 }

spring-shell2-standard-commands/src/main/java/org/springframework/shell2/standard/commands/Stacktrace.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2017 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
+ *
+ *      http://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.shell2.standard.commands;
+
+import org.jline.terminal.Terminal;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.shell2.result.ThrowableResultHandler;
+import org.springframework.shell2.standard.ShellComponent;
+import org.springframework.shell2.standard.ShellMethod;
+
+/**
+ * A command to display the full stacktrace when an error occurs.
+ */
+@ShellComponent
+public class Stacktrace {
+
+	@Autowired
+	private Terminal terminal;
+
+	@Autowired
+	private ThrowableResultHandler throwableResultHandler;
+
+
+	@ShellMethod(value = ThrowableResultHandler.DETAILS_COMMAND_NAME, help = "Display the full stacktrace of the last error")
+	public void stacktrace() {
+		if (throwableResultHandler.getLastError() != null) {
+			throwableResultHandler.getLastError().printStackTrace(terminal.writer());
+		}
+	}
+}