Fix handling of required options

Author: fmbenhassine

spring-shell-core/src/main/java/org/springframework/shell/core/command/adapter/MethodInvokerCommandAdapter.java

@@ -135,21 +135,33 @@ private List<Object> prepareArguments(CommandContext commandContext) {
 				log.debug("Processing option for parameter: " + parameters[i].getName());
 				char shortName = optionAnnotation.shortName();
 				String longName = optionAnnotation.longName();
+				boolean required = optionAnnotation.required();
 				CommandOption commandOption = commandContext
 					.getOptionByName(longName.isEmpty() ? String.valueOf(shortName) : longName);
-				if (commandOption == null) {
-					// Option not provided, use default value
-					String defaultValue = optionAnnotation.defaultValue();
-					Class<?> parameterType = parameterTypes[i];
-					Object value = this.conversionService.convert(defaultValue, parameterType);
-					args.add(value);
-				}
-				else {
+				if (commandOption != null) {
 					String rawValue = commandOption.value();
 					Class<?> parameterType = parameterTypes[i];
 					Object value = this.conversionService.convert(rawValue, parameterType);
 					args.add(value);
 				}
+				else {
+					if (required) {
+						throw new IllegalArgumentException(
+								"Required option '--" + (longName.isEmpty() ? shortName : longName) + "' is missing.");
+					}
+					else {
+						// try to use default value
+						String defaultValue = optionAnnotation.defaultValue();
+						if (defaultValue.isEmpty()) {
+							log.warn("No value provided for optional option '--"
+									+ (longName.isEmpty() ? shortName : longName)
+									+ "' and no default value specified.");
+						}
+						Class<?> parameterType = parameterTypes[i];
+						Object value = this.conversionService.convert(defaultValue, parameterType);
+						args.add(value);
+					}
+				}
 				continue;
 			}
 			// Handle Argument injection

spring-shell-samples/spring-shell-sample-petclinic/src/main/java/org/springframework/shell/samples/petclinic/commands/PetCommands.java

@@ -52,7 +52,8 @@ public void listPets(CommandContext commandContext) {
 
 	@Command(name = { "pets", "info" }, description = "Show detail about a given pet", group = "Pets",
 			help = "Show the details about a given pet")
-	public void showPet(@Option(longName = "petId", description = "The pet ID") int id, CommandContext commandContext) {
+	public void showPet(@Option(longName = "petId", description = "The pet ID", required = true) int id,
+			CommandContext commandContext) {
 		try {
 			Pet pet = this.jdbcClient.sql("SELECT * FROM PETS where id = " + id)
 				.query(new DataClassRowMapper<>(Pet.class))