Add support for exit codes

- New configurations to CommandRegistration
- Re-using exit code concepts from boot
- Handling exit codes only in non-interactive mode
- Adding e2e commands and tests for better coverage
- Fixes #431

spring-shell-autoconfigure/src/main/java/org/springframework/shell/boot/ExitCodeAutoConfiguration.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright 2022 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.boot;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Function;
+
+import org.springframework.boot.ExitCodeExceptionMapper;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.shell.command.CommandExecution;
+import org.springframework.shell.exit.ExitCodeMappings;
+
+/**
+ * {@link EnableAutoConfiguration Auto-configuration} for exit codes.
+ *
+ * @author Janne Valkealahti
+ */
+@Configuration(proxyBeanMethods = false)
+public class ExitCodeAutoConfiguration {
+
+	@Bean
+	@ConditionalOnMissingBean
+	public ShellExitCodeExceptionMapper shellExitCodeExceptionMapper() {
+		return new ShellExitCodeExceptionMapper();
+	}
+
+	@Bean
+	@ConditionalOnMissingBean
+	public ShellExitCodeMappingsExceptionMapper shellExitCodeMappingsExceptionMapper() {
+		return new ShellExitCodeMappingsExceptionMapper();
+	}
+
+	static class ShellExitCodeExceptionMapper implements ExitCodeExceptionMapper {
+
+		@Override
+		public int getExitCode(Throwable exception) {
+			if (exception.getCause() instanceof CommandExecution.CommandParserExceptionsException) {
+				return 2;
+			}
+			return 1;
+		}
+	}
+
+	static class ShellExitCodeMappingsExceptionMapper implements ExitCodeExceptionMapper, ExitCodeMappings {
+
+		private final List<Function<Throwable, Integer>> functions = new ArrayList<>();
+
+		@Override
+		public void reset(List<Function<Throwable, Integer>> functions) {
+			this.functions.clear();
+			if (functions != null) {
+				this.functions.addAll(functions);
+			}
+		}
+
+		@Override
+		public int getExitCode(Throwable exception) {
+			int exitCode = 0;
+			for (Function<Throwable, Integer> function : functions) {
+				Integer code = function.apply(exception.getCause());
+				if (code != null) {
+					if (code > 0 && code > exitCode || code < 0 && code < exitCode) {
+						exitCode = code;
+					}
+				}
+			}
+			return exitCode;
+		}
+	}
+}

spring-shell-autoconfigure/src/main/java/org/springframework/shell/boot/SpringShellAutoConfiguration.java

@@ -34,6 +34,8 @@ import org.springframework.shell.ResultHandler;
 import org.springframework.shell.ResultHandlerService;
 import org.springframework.shell.Shell;
 import org.springframework.shell.command.CommandCatalog;
+import org.springframework.shell.context.ShellContext;
+import org.springframework.shell.exit.ExitCodeMappings;
 import org.springframework.shell.result.GenericResultHandlerService;
 import org.springframework.shell.result.ResultHandlerConfig;
 
@@ -65,8 +67,9 @@ public class SpringShellAutoConfiguration {
 
 	@Bean
 	public Shell shell(ResultHandlerService resultHandlerService, CommandCatalog commandRegistry, Terminal terminal,
-			@Qualifier("shellConversionService") ConversionService shellConversionService) {
-		Shell shell = new Shell(resultHandlerService, commandRegistry, terminal);
+			@Qualifier("shellConversionService") ConversionService shellConversionService, ShellContext shellContext,
+			ExitCodeMappings exitCodeMappings) {
+		Shell shell = new Shell(resultHandlerService, commandRegistry, terminal, shellContext, exitCodeMappings);
 		shell.setConversionService(shellConversionService);
 		return shell;
 	}

spring-shell-autoconfigure/src/main/resources/META-INF/spring.factories

@@ -1,4 +1,5 @@
 org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
+org.springframework.shell.boot.ExitCodeAutoConfiguration,\
 org.springframework.shell.boot.ShellContextAutoConfiguration,\
 org.springframework.shell.boot.SpringShellAutoConfiguration,\
 org.springframework.shell.boot.ShellRunnerAutoConfiguration,\