Fix option type parsing

- In `CommandRegistration` add `ResolvableType` for `OptionSpec` giving
  more spesific handling of a type.
- In `CommandParser` handle source and target types so that we
  have generics with `List`, `Set` and arrays working better.
- In `HandlerMethodArgumentResolver` add better handling for
  `ConversionService` for generic types.
- In `StandardMethodTargetRegistrar` add better types via `ResolvableType`
  now that `CommandRegistration` support it.
- In `OptionConversionCommands` remove converter from `String` to `Set` as
  now things should work as is if generic in a `Set` has a converter.
- Backport #694 #699
- Fixes #700

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

@@ -24,8 +24,10 @@ import jakarta.validation.Validator;
 import org.jline.terminal.Terminal;
 
 import org.springframework.core.MethodParameter;
+import org.springframework.core.ResolvableType;
 import org.springframework.core.annotation.Order;
 import org.springframework.core.convert.ConversionService;
+import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.handler.invocation.HandlerMethodArgumentResolver;
 import org.springframework.messaging.support.MessageBuilder;
@@ -253,7 +255,13 @@ public interface CommandExecution {
 
 		@Override
 		public Object resolveArgument(MethodParameter parameter, Message<?> message) throws Exception {
-			return conversionService.convert(paramValues.get(parameter.getParameterName()), parameter.getParameterType());
+			Object source = paramValues.get(parameter.getParameterName());
+			if (source == null) {
+				return null;
+			}
+			TypeDescriptor sourceType = new TypeDescriptor(ResolvableType.forClass(source.getClass()), null, null);
+			TypeDescriptor targetType = new TypeDescriptor(parameter);
+			return conversionService.convert(source, sourceType, targetType);
 		}
 
 	}

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

@@ -175,13 +175,27 @@ public interface CommandRegistration {
 		OptionSpec shortNames(Character... names);
 
 		/**
-		 * Define a type for an option.
+		 * Define a type for an option. This method is a shortcut for
+		 * {@link #type(ResolvableType)} which is a preferred way to
+		 * define type with generics. Will override one from
+		 * {@link #type(ResolvableType)}.
 		 *
 		 * @param type the type
 		 * @return option spec for chaining
+		 * @see #type(ResolvableType)
 		 */
 		OptionSpec type(Type type);
 
+		/**
+		 * Define a {@link ResolvableType} for an option. This method is
+		 * a preferred way to define type with generics. Will override one
+		 * from {@link #type(Type)}.
+		 *
+		 * @param type the resolvable type
+		 * @return option spec for chaining
+		 */
+		OptionSpec type(ResolvableType type);
+
 		/**
 		 * Define a {@code description} for an option.
 		 *
@@ -817,6 +831,12 @@ public interface CommandRegistration {
 			return this;
 		}
 
+		@Override
+		public OptionSpec type(ResolvableType type) {
+			this.type = type;
+			return this;
+		}
+
 		@Override
 		public OptionSpec description(String description) {
 			this.description = description;

spring-shell-core/src/main/java/org/springframework/shell/command/parser/Parser.java

@@ -27,6 +27,7 @@ import java.util.stream.Stream;
 
 import org.springframework.core.ResolvableType;
 import org.springframework.core.convert.ConversionService;
+import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.shell.command.CommandOption;
 import org.springframework.shell.command.CommandRegistration;
@@ -204,7 +205,8 @@ public interface Parser {
 						optionResults.add(OptionResult.of(o, null));
 					}
 					else {
-						Object value = convertOptionType(o, asdf);
+						Object toConvertValue = asdf.size() == 1 ? asdf.get(0) : asdf;
+						Object value = convertOptionType(o, toConvertValue);
 						optionResults.add(OptionResult.of(o, value));
 					}
 
@@ -362,8 +364,11 @@ public interface Parser {
 				return true;
 			}
 			if (conversionService != null && option.getType() != null && value != null) {
-				if (conversionService.canConvert(value.getClass(), option.getType().getRawClass())) {
-					value = conversionService.convert(value, option.getType().getRawClass());
+				Object source = value;
+				TypeDescriptor sourceType = new TypeDescriptor(ResolvableType.forClass(source.getClass()), null, null);
+				TypeDescriptor targetType = new TypeDescriptor(option.getType(), null, null);
+				if (conversionService.canConvert(sourceType, targetType)) {
+					value = conversionService.convert(source, sourceType, targetType);
 				}
 			}
 			return value;