Rework completion interfaces

- Use same interface type in a generic interactive completions
  in a method level and option value level.
- Change CompletionResolver to have same function signature
  as with options and use CompletionContext to keep
  relevant information.
- Fixes #449

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

@@ -1,3 +1,18 @@
+/*
+ * 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;
@@ -11,7 +26,7 @@ import org.springframework.shell.command.ArgumentHeaderMethodArgumentResolver;
 import org.springframework.shell.command.CommandContextMethodArgumentResolver;
 import org.springframework.shell.command.CommandExecution.CommandExecutionHandlerMethodArgumentResolvers;
 import org.springframework.shell.completion.CompletionResolver;
-import org.springframework.shell.completion.DefaultCompletionResolver;
+import org.springframework.shell.completion.RegistrationOptionsCompletionResolver;
 import org.springframework.shell.config.ShellConversionServiceSupplier;
 import org.springframework.shell.standard.ShellOptionMethodArgumentResolver;
 
@@ -20,7 +35,7 @@ public class ParameterResolverAutoConfiguration {
 
 	@Bean
 	public CompletionResolver defaultCompletionResolver() {
-		return new DefaultCompletionResolver();
+		return new RegistrationOptionsCompletionResolver();
 	}
 
 	@Bean

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

@@ -105,7 +105,17 @@ public class CompletionContext {
 				position, commandRegistration, commandOption);
 	}
 
+	/**
+	 * Return a copy of this context with given command option.
+	 */
 	public CompletionContext commandOption(CommandOption commandOption) {
 		return new CompletionContext(words, wordIndex, position, commandRegistration, commandOption);
 	}
+
+	/**
+	 * Return a copy of this context with given command registration.
+	 */
+	public CompletionContext commandRegistration(CommandRegistration commandRegistration) {
+		return new CompletionContext(words, wordIndex, position, commandRegistration, commandOption);
+	}
 }

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

@@ -277,11 +277,12 @@ public class Shell {
 
 		String best = findLongestCommand(prefix);
 		if (best != null) {
-			CompletionContext argsContext = context.drop(best.split(" ").length);
+			context = context.drop(best.split(" ").length);
 			CommandRegistration registration = commandRegistry.getRegistrations().get(best);
+			CompletionContext argsContext = context.commandRegistration(registration);
 
 			for (CompletionResolver resolver : completionResolvers) {
-				List<CompletionProposal> resolved = resolver.resolve(registration, argsContext);
+				List<CompletionProposal> resolved = resolver.apply(argsContext);
 				candidates.addAll(resolved);
 			}
 

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

@@ -15,12 +15,8 @@
  */
 package org.springframework.shell.command;
 
-import java.util.List;
-import java.util.function.Function;
-
 import org.springframework.core.ResolvableType;
-import org.springframework.shell.CompletionContext;
-import org.springframework.shell.CompletionProposal;
+import org.springframework.shell.completion.CompletionResolver;
 
 /**
  * Interface representing an option in a command.
@@ -104,7 +100,7 @@ public interface CommandOption {
 	 *
 	 * @return the completion function
 	 */
-	Function<CompletionContext, List<CompletionProposal>> getCompletion();
+	CompletionResolver getCompletion();
 
 	/**
 	 * Gets an instance of a default {@link CommandOption}.
@@ -150,7 +146,7 @@ public interface CommandOption {
 	 */
 	public static CommandOption of(String[] longNames, Character[] shortNames, String description,
 			ResolvableType type, boolean required, String defaultValue, Integer position, Integer arityMin,
-			Integer arityMax, String label, Function<CompletionContext, List<CompletionProposal>> completion) {
+			Integer arityMax, String label, CompletionResolver completion) {
 		return new DefaultCommandOption(longNames, shortNames, description, type, required, defaultValue, position,
 				arityMin, arityMax, label, completion);
 	}
@@ -170,12 +166,12 @@ public interface CommandOption {
 		private int arityMin;
 		private int arityMax;
 		private String label;
-		private Function<CompletionContext, List<CompletionProposal>> completion;
+		private CompletionResolver completion;
 
 		public DefaultCommandOption(String[] longNames, Character[] shortNames, String description,
 				ResolvableType type, boolean required, String defaultValue, Integer position,
 				Integer arityMin, Integer arityMax, String label,
-				Function<CompletionContext, List<CompletionProposal>> completion) {
+				CompletionResolver completion) {
 			this.longNames = longNames != null ? longNames : new String[0];
 			this.shortNames = shortNames != null ? shortNames : new Character[0];
 			this.description = description;
@@ -240,7 +236,7 @@ public interface CommandOption {
 		}
 
 		@Override
-		public Function<CompletionContext, List<CompletionProposal>> getCompletion() {
+		public CompletionResolver getCompletion() {
 			return completion;
 		}
 	}

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

@@ -29,8 +29,7 @@ import java.util.stream.Stream;
 import org.springframework.core.ResolvableType;
 import org.springframework.lang.Nullable;
 import org.springframework.shell.Availability;
-import org.springframework.shell.CompletionContext;
-import org.springframework.shell.CompletionProposal;
+import org.springframework.shell.completion.CompletionResolver;
 import org.springframework.shell.context.InteractionMode;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
@@ -216,7 +215,7 @@ public interface CommandRegistration {
 		 * @param completion the completion function
 		 * @return option spec for chaining
 		 */
-		OptionSpec completion(Function<CompletionContext, List<CompletionProposal>> completion);
+		OptionSpec completion(CompletionResolver completion);
 
 		/**
 		 * Return a builder for chaining.
@@ -538,7 +537,7 @@ public interface CommandRegistration {
 		private Integer arityMin;
 		private Integer arityMax;
 		private String label;
-		private Function<CompletionContext, List<CompletionProposal>> completion;
+		private CompletionResolver completion;
 
 		DefaultOptionSpec(BaseBuilder builder) {
 			this.builder = builder;
@@ -638,7 +637,7 @@ public interface CommandRegistration {
 		}
 
 		@Override
-		public OptionSpec completion(Function<CompletionContext, List<CompletionProposal>> completion) {
+		public OptionSpec completion(CompletionResolver completion) {
 			this.completion = completion;
 			return this;
 		}
@@ -688,7 +687,7 @@ public interface CommandRegistration {
 			return label;
 		}
 
-		public Function<CompletionContext, List<CompletionProposal>> getCompletion() {
+		public CompletionResolver getCompletion() {
 			return completion;
 		}
 	}

spring-shell-core/src/main/java/org/springframework/shell/completion/CompletionResolver.java

@@ -16,24 +16,16 @@
 package org.springframework.shell.completion;
 
 import java.util.List;
+import java.util.function.Function;
 
 import org.springframework.shell.CompletionContext;
 import org.springframework.shell.CompletionProposal;
-import org.springframework.shell.command.CommandRegistration;
 
 /**
  * Interface resolving completion proposals.
  *
  * @author Janne Valkealahti
  */
-public interface CompletionResolver {
-
-	/**
-	 * Resolve completions.
-	 *
-	 * @param registration the command registration
-	 * @param context the completion context
-	 * @return list of resolved completions
-	 */
-	List<CompletionProposal> resolve(CommandRegistration registration, CompletionContext context);
+@FunctionalInterface
+public interface CompletionResolver extends Function<CompletionContext, List<CompletionProposal>> {
 }

spring-shell-core/src/main/java/org/springframework/shell/completion/RegistrationOptionsCompletionResolver.java

@@ -16,28 +16,31 @@
 package org.springframework.shell.completion;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.stream.Stream;
 
 import org.springframework.shell.CompletionContext;
 import org.springframework.shell.CompletionProposal;
-import org.springframework.shell.command.CommandRegistration;
 
 /**
  * Default implementation of a {@link CompletionResolver}.
  *
  * @author Janne Valkealahti
  */
-public class DefaultCompletionResolver implements CompletionResolver {
+public class RegistrationOptionsCompletionResolver implements CompletionResolver {
 
 	@Override
-	public List<CompletionProposal> resolve(CommandRegistration registration, CompletionContext context) {
+	public List<CompletionProposal> apply(CompletionContext context) {
+		if (context.getCommandRegistration() == null) {
+			return Collections.emptyList();
+		}
 		List<CompletionProposal> candidates = new ArrayList<>();
-		registration.getOptions().stream()
+		context.getCommandRegistration().getOptions().stream()
 			.flatMap(o -> Stream.of(o.getLongNames()))
 			.map(ln -> new CompletionProposal("--" + ln))
 			.forEach(candidates::add);
-		registration.getOptions().stream()
+		context.getCommandRegistration().getOptions().stream()
 			.flatMap(o -> Stream.of(o.getShortNames()))
 			.map(ln -> new CompletionProposal("-" + ln))
 			.forEach(candidates::add);

spring-shell-core/src/test/java/org/springframework/shell/ShellTests.java

@@ -30,7 +30,7 @@ import org.mockito.junit.jupiter.MockitoExtension;
 
 import org.springframework.shell.command.CommandCatalog;
 import org.springframework.shell.command.CommandRegistration;
-import org.springframework.shell.completion.CompletionResolver;
+import org.springframework.shell.completion.RegistrationOptionsCompletionResolver;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.fail;
@@ -56,9 +56,6 @@ public class ShellTests {
 	@Mock
 	CommandCatalog commandRegistry;
 
-	@Mock
-	private CompletionResolver completionResolver;
-
 	@InjectMocks
 	private Shell shell;
 
@@ -66,7 +63,7 @@ public class ShellTests {
 
 	@BeforeEach
 	public void setUp() {
-		shell.setCompletionResolvers(Arrays.asList(completionResolver));
+		shell.setCompletionResolvers(Arrays.asList(new RegistrationOptionsCompletionResolver()));
 	}
 
 	@Test
@@ -272,7 +269,6 @@ public class ShellTests {
 
 	@Test
 	public void completionArgWithMethod() throws Exception {
-		when(completionResolver.resolve(any(), any())).thenReturn(Arrays.asList(new CompletionProposal("--arg1")));
 		CommandRegistration registration1 = CommandRegistration.builder()
 			.command("hello world")
 			.withTarget()
@@ -294,7 +290,6 @@ public class ShellTests {
 
 	@Test
 	public void completionArgWithFunction() throws Exception {
-		when(completionResolver.resolve(any(), any())).thenReturn(Arrays.asList(new CompletionProposal("--arg1")));
 		CommandRegistration registration1 = CommandRegistration.builder()
 			.command("hello world")
 			.withTarget()

spring-shell-standard/src/main/java/org/springframework/shell/standard/StandardMethodTargetRegistrar.java

@@ -23,7 +23,6 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import java.util.function.Function;
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
@@ -37,7 +36,6 @@ import org.springframework.core.MethodParameter;
 import org.springframework.core.annotation.AnnotationUtils;
 import org.springframework.messaging.handler.invocation.InvocableHandlerMethod;
 import org.springframework.shell.Availability;
-import org.springframework.shell.CompletionContext;
 import org.springframework.shell.CompletionProposal;
 import org.springframework.shell.MethodTargetRegistrar;
 import org.springframework.shell.Utils;
@@ -45,6 +43,7 @@ import org.springframework.shell.command.CommandCatalog;
 import org.springframework.shell.command.CommandRegistration;
 import org.springframework.shell.command.CommandRegistration.Builder;
 import org.springframework.shell.command.CommandRegistration.OptionSpec;
+import org.springframework.shell.completion.CompletionResolver;
 import org.springframework.shell.standard.ShellOption.NoValueProvider;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
@@ -149,12 +148,12 @@ public class StandardMethodTargetRegistrar implements MethodTargetRegistrar, App
 								optionSpec.required();
 							}
 							if (!ClassUtils.isAssignable(NoValueProvider.class, so.valueProvider())) {
-								Function<CompletionContext, List<CompletionProposal>> completionFunction = ctx -> {
+								CompletionResolver completionResolver = ctx -> {
 									ValueProvider valueProviderBean = this.applicationContext.getBean(so.valueProvider());
 									List<CompletionProposal> complete = valueProviderBean.complete(ctx);
 									return complete;
 								};
-								optionSpec.completion(completionFunction);
+								optionSpec.completion(completionResolver);
 							}
 						}
 					}