Add support for custom completion providers

- Add attribute in Command annotation to specify custom completion provider
- Move command completion APIs under command package
- Remove ValueProvider as it is a duplicate of CompletionProvider
- Remove unused OptionValues annotation

Author: fmbenhassine

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

@@ -32,8 +32,8 @@
 @ConditionalOnMissingBean(annotation = EnableCommand.class)
 @ImportAutoConfiguration({ ApplicationRunnerAutoConfiguration.class, CommandRegistryAutoConfiguration.class,
 		ComponentFlowAutoConfiguration.class, JLineShellAutoConfiguration.class, ShellRunnerAutoConfiguration.class,
-		StandardAPIAutoConfiguration.class, StandardCommandsAutoConfiguration.class, TerminalUIAutoConfiguration.class,
-		ThemingAutoConfiguration.class, UserConfigAutoConfiguration.class })
+		StandardCommandsAutoConfiguration.class, TerminalUIAutoConfiguration.class, ThemingAutoConfiguration.class,
+		UserConfigAutoConfiguration.class })
 public class SpringShellAutoConfiguration {
 
 }

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

@@ -17,6 +17,7 @@
 
 import java.io.PrintWriter;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
 
@@ -28,6 +29,7 @@
 import org.springframework.shell.core.command.availability.Availability;
 import org.springframework.shell.core.command.availability.AvailabilityProvider;
 import org.springframework.shell.core.command.exit.ExitStatusExceptionMapper;
+import org.springframework.shell.core.command.completion.CompletionProvider;
 
 /**
  * Base class helping to build shell commands.
@@ -52,6 +54,8 @@ public abstract class AbstractCommand implements Command {
 
 	@Nullable private ExitStatusExceptionMapper exitStatusExceptionMapper;
 
+	private CompletionProvider completionProvider = context -> Collections.emptyList();
+
 	private List<String> aliases = new ArrayList<>();
 
 	public AbstractCommand(String name, String description) {
@@ -121,6 +125,15 @@ public void setExitStatusExceptionMapper(ExitStatusExceptionMapper exitStatusExc
 		this.exitStatusExceptionMapper = exitStatusExceptionMapper;
 	}
 
+	@Override
+	public CompletionProvider getCompletionProvider() {
+		return completionProvider;
+	}
+
+	public void setCompletionProvider(CompletionProvider completionProvider) {
+		this.completionProvider = completionProvider;
+	}
+
 	@Override
 	public ExitStatus execute(CommandContext commandContext) throws Exception {
 		Availability availability = getAvailabilityProvider().get();

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

@@ -28,6 +28,7 @@
 import org.springframework.shell.core.command.adapter.FunctionCommandAdapter;
 import org.springframework.shell.core.command.availability.AvailabilityProvider;
 import org.springframework.shell.core.command.exit.ExitStatusExceptionMapper;
+import org.springframework.shell.core.command.completion.CompletionProvider;
 import org.springframework.util.Assert;
 
 /**
@@ -94,6 +95,14 @@ default AvailabilityProvider getAvailabilityProvider() {
 		return AvailabilityProvider.alwaysAvailable();
 	}
 
+	/**
+	 * Get the completion provider of the command.
+	 * @return the completion provider of the command
+	 */
+	default CompletionProvider getCompletionProvider() {
+		return context -> Collections.emptyList();
+	}
+
 	/**
 	 * Execute the command within the given context.
 	 * @param commandContext the context of the command
@@ -130,6 +139,8 @@ final class Builder {
 
 		private AvailabilityProvider availabilityProvider = AvailabilityProvider.alwaysAvailable();
 
+		private CompletionProvider completionProvider = context -> Collections.emptyList();
+
 		@Nullable ExitStatusExceptionMapper exitStatusExceptionMapper;
 
 		private List<String> aliases = new ArrayList<>();
@@ -169,6 +180,11 @@ public Builder exitStatusExceptionMapper(ExitStatusExceptionMapper exitStatusExc
 			return this;
 		}
 
+		public Builder completionProvider(CompletionProvider completionProvider) {
+			this.completionProvider = completionProvider;
+			return this;
+		}
+
 		public Builder aliases(String... aliases) {
 			this.aliases = Arrays.asList(aliases);
 			return this;
@@ -181,6 +197,7 @@ public AbstractCommand execute(Consumer<CommandContext> commandExecutor) {
 					commandExecutor);
 			command.setAliases(aliases);
 			command.setAvailabilityProvider(availabilityProvider);
+			command.setCompletionProvider(completionProvider);
 			if (exitStatusExceptionMapper != null) {
 				command.setExitStatusExceptionMapper(exitStatusExceptionMapper);
 			}
@@ -195,6 +212,7 @@ public AbstractCommand execute(Function<CommandContext, String> commandExecutor)
 					commandExecutor);
 			command.setAliases(aliases);
 			command.setAvailabilityProvider(availabilityProvider);
+			command.setCompletionProvider(completionProvider);
 			if (exitStatusExceptionMapper != null) {
 				command.setExitStatusExceptionMapper(exitStatusExceptionMapper);
 			}

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

@@ -99,4 +99,10 @@
 	 */
 	String exitStatusExceptionMapper() default "";
 
+	/**
+	 * Define completion provider bean name.
+	 * @return the completion provider bean name
+	 */
+	String completionProvider() default "";
+
 }

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

@@ -17,6 +17,7 @@
 
 import java.lang.reflect.Method;
 import java.util.Arrays;
+import java.util.Collections;
 
 import jakarta.validation.Validator;
 
@@ -36,6 +37,7 @@
 import org.springframework.shell.core.command.adapter.MethodInvokerCommandAdapter;
 import org.springframework.shell.core.command.availability.AvailabilityProvider;
 import org.springframework.shell.core.command.exit.ExitStatusExceptionMapper;
+import org.springframework.shell.core.command.completion.CompletionProvider;
 import org.springframework.shell.core.utils.Utils;
 import org.springframework.util.Assert;
 
@@ -76,6 +78,7 @@ public Command getObject() {
 		String[] aliases = command.alias();
 		String availabilityProvider = command.availabilityProvider();
 		String exitStatusExceptionMapper = command.exitStatusExceptionMapper();
+		String completionProviderBeanName = command.completionProvider();
 		log.debug("Creating command bean for method '" + this.method + "' with name '" + name + "'");
 		Class<?> declaringClass = this.method.getDeclaringClass();
 		Object targetObject;
@@ -127,10 +130,23 @@ Ensure that the declaring class is annotated with a Spring stereotype annotation
 		catch (BeansException e) {
 			log.debug("No Validator bean found, using default validator.");
 		}
+		CompletionProvider completionProvider = CompletionContext -> Collections.emptyList();
+		if (!completionProviderBeanName.isEmpty()) {
+			try {
+				completionProvider = this.applicationContext.getBean(completionProviderBeanName,
+						CompletionProvider.class);
+			}
+			catch (BeansException e) {
+				log.debug("No CompletionProvider bean found with name '" + completionProviderBeanName
+						+ "', using default completion provider.");
+			}
+		}
+
 		MethodInvokerCommandAdapter methodInvokerCommandAdapter = new MethodInvokerCommandAdapter(name, description,
 				group, help, hidden, this.method, targetObject, configurableConversionService, validator);
 		methodInvokerCommandAdapter.setAliases(Arrays.stream(aliases).toList());
 		methodInvokerCommandAdapter.setAvailabilityProvider(availabilityProviderBean);
+		methodInvokerCommandAdapter.setCompletionProvider(completionProvider);
 		if (exitStatusExceptionMapperBean != null) {
 			methodInvokerCommandAdapter.setExitStatusExceptionMapper(exitStatusExceptionMapperBean);
 		}

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

@@ -14,32 +14,30 @@
  * limitations under the License.
  */
 
-package org.springframework.shell.core;
+package org.springframework.shell.core.command.completion;
 
 import java.util.List;
 import java.util.stream.Collectors;
 
 import org.springframework.shell.core.command.CommandRegistry;
-import org.springframework.shell.core.completion.CompletionContext;
-import org.springframework.shell.core.completion.CompletionProposal;
 
 /**
- * A {@link ValueProvider} that can be used to auto-complete names of shell commands.
+ * A {@link CompletionProvider} that can be used to auto-complete names of shell commands.
  *
  * @author Eric Bottard
  * @author Janne Valkealahti
  * @author Mahmoud Ben Hassine
  */
-public class CommandValueProvider implements ValueProvider {
+public class CommandNameCompletionProvider implements CompletionProvider {
 
 	private final CommandRegistry commandRegistry;
 
-	public CommandValueProvider(CommandRegistry commandRegistry) {
+	public CommandNameCompletionProvider(CommandRegistry commandRegistry) {
 		this.commandRegistry = commandRegistry;
 	}
 
 	@Override
-	public List<CompletionProposal> complete(CompletionContext completionContext) {
+	public List<CompletionProposal> apply(CompletionContext completionContext) {
 		return commandRegistry.getCommands()
 			.stream()
 			.map(command -> new CompletionProposal(command.getName()))

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

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package org.springframework.shell.core.completion;
+package org.springframework.shell.core.command.completion;
 
 import org.jspecify.annotations.Nullable;
 import org.springframework.shell.core.command.CommandOption;