Implement interactive completion

- This is a re-implementation of a interactive completion
  with breaking changes as it moves away from a direct use
  of a MethodParameter in favour of a CommandRegistration
  and its option definitions.
- Fixes #449

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

@@ -20,6 +20,9 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.stream.Collectors;
 
+import org.springframework.shell.command.CommandOption;
+import org.springframework.shell.command.CommandRegistration;
+
 /**
  * Represents the buffer context in which completion was triggered.
  *
@@ -33,16 +36,22 @@ public class CompletionContext {
 
 	private final int position;
 
+	private final CommandOption commandOption;
+
+	private final CommandRegistration commandRegistration;
+
 	/**
 	 *
 	 * @param words words in the buffer, excluding words for the command name
 	 * @param wordIndex the index of the word the cursor is in
 	 * @param position the position inside the current word where the cursor is
 	 */
-	public CompletionContext(List<String> words, int wordIndex, int position) {
+	public CompletionContext(List<String> words, int wordIndex, int position, CommandRegistration commandRegistration,  CommandOption commandOption) {
 		this.words = words;
 		this.wordIndex = wordIndex;
 		this.position = position;
+		this.commandRegistration = commandRegistration;
+		this.commandOption = commandOption;
 	}
 
 	public List<String> getWords() {
@@ -57,6 +66,14 @@ public class CompletionContext {
 		return position;
 	}
 
+	public CommandOption getCommandOption() {
+		return commandOption;
+	}
+
+	public CommandRegistration getCommandRegistration() {
+		return commandRegistration;
+	}
+
 	public String upToCursor() {
 		String start = words.subList(0, wordIndex).stream().collect(Collectors.joining(" "));
 		if (wordIndex < words.size()) {
@@ -84,6 +101,11 @@ public class CompletionContext {
 	 * Return a copy of this context, as if the first {@literal nbWords} were not present
 	 */
 	public CompletionContext drop(int nbWords) {
-		return new CompletionContext(new ArrayList<String>(words.subList(nbWords, words.size())), wordIndex-nbWords, position);
+		return new CompletionContext(new ArrayList<String>(words.subList(nbWords, words.size())), wordIndex - nbWords,
+				position, commandRegistration, commandOption);
+	}
+
+	public CompletionContext commandOption(CommandOption commandOption) {
+		return new CompletionContext(words, wordIndex, position, commandRegistration, commandOption);
 	}
 }

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

@@ -22,6 +22,7 @@ import java.util.List;
 import java.util.Optional;
 import java.util.function.Function;
 import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import javax.validation.Validator;
 import javax.validation.ValidatorFactory;
@@ -38,6 +39,7 @@ import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.shell.command.CommandAlias;
 import org.springframework.shell.command.CommandCatalog;
 import org.springframework.shell.command.CommandExecution;
+import org.springframework.shell.command.CommandOption;
 import org.springframework.shell.command.CommandExecution.CommandExecutionException;
 import org.springframework.shell.command.CommandExecution.CommandExecutionHandlerMethodArgumentResolvers;
 import org.springframework.shell.command.CommandRegistration;
@@ -45,6 +47,7 @@ import org.springframework.shell.completion.CompletionResolver;
 import org.springframework.shell.context.InteractionMode;
 import org.springframework.shell.context.ShellContext;
 import org.springframework.shell.exit.ExitCodeMappings;
+import org.springframework.util.StringUtils;
 
 /**
  * Main class implementing a shell loop.
@@ -275,17 +278,83 @@ public class Shell {
 		String best = findLongestCommand(prefix);
 		if (best != null) {
 			CompletionContext argsContext = context.drop(best.split(" ").length);
-			// Try to complete arguments
 			CommandRegistration registration = commandRegistry.getRegistrations().get(best);
 
 			for (CompletionResolver resolver : completionResolvers) {
 				List<CompletionProposal> resolved = resolver.resolve(registration, argsContext);
 				candidates.addAll(resolved);
 			}
+
+			// Try to complete arguments
+			List<CommandOption> matchedArgOptions = new ArrayList<>();
+			if (argsContext.getWords().size() > 0) {
+				matchedArgOptions.addAll(matchOptions(registration.getOptions(), argsContext.getWords().get(0)));
+			}
+
+			List<CompletionProposal> argProposals =	matchedArgOptions.stream()
+				.flatMap(o -> {
+					Function<CompletionContext, List<CompletionProposal>> completion = o.getCompletion();
+					if (completion != null) {
+						List<CompletionProposal> apply = completion.apply(argsContext.commandOption(o));
+						return apply.stream();
+					}
+					return Stream.empty();
+				})
+				.collect(Collectors.toList());
+
+			candidates.addAll(argProposals);
 		}
 		return candidates;
 	}
 
+	private List<CommandOption> matchOptions(List<CommandOption> options, String arg) {
+		List<CommandOption> matched = new ArrayList<>();
+		String trimmed = StringUtils.trimLeadingCharacter(arg, '-');
+		int count = arg.length() - trimmed.length();
+		if (count == 1) {
+			if (trimmed.length() == 1) {
+				Character trimmedChar = trimmed.charAt(0);
+				options.stream()
+					.filter(o -> {
+						for (Character sn : o.getShortNames()) {
+							if (trimmedChar.equals(sn)) {
+								return true;
+							}
+						}
+						return false;
+					})
+				.findFirst()
+				.ifPresent(o -> matched.add(o));
+			}
+			else if (trimmed.length() > 1) {
+				trimmed.chars().mapToObj(i -> (char)i)
+					.forEach(c -> {
+						options.stream().forEach(o -> {
+							for (Character sn : o.getShortNames()) {
+								if (c.equals(sn)) {
+									matched.add(o);
+								}
+							}
+						});
+					});
+			}
+		}
+		else if (count == 2) {
+			options.stream()
+				.filter(o -> {
+					for (String ln : o.getLongNames()) {
+						if (trimmed.equals(ln)) {
+							return true;
+						}
+					}
+					return false;
+				})
+				.findFirst()
+				.ifPresent(o -> matched.add(o));
+		}
+		return matched;
+	}
+
 	private List<CompletionProposal> commandsStartingWith(String prefix) {
 		// Workaround for https://github.com/spring-projects/spring-shell/issues/150
 		// (sadly, this ties this class to JLine somehow)

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

@@ -15,7 +15,12 @@
  */
 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;
 
 /**
  * Interface representing an option in a command.
@@ -94,6 +99,13 @@ public interface CommandOption {
 	 */
 	String getLabel();
 
+	/**
+	 * Gets a completion function.
+	 *
+	 * @return the completion function
+	 */
+	Function<CompletionContext, List<CompletionProposal>> getCompletion();
+
 	/**
 	 * Gets an instance of a default {@link CommandOption}.
 	 *
@@ -103,7 +115,7 @@ public interface CommandOption {
 	 * @return default command option
 	 */
 	public static CommandOption of(String[] longNames, Character[] shortNames, String description) {
-		return of(longNames, shortNames, description, null, false, null, null, null, null, null);
+		return of(longNames, shortNames, description, null, false, null, null, null, null, null, null);
 	}
 
 	/**
@@ -117,7 +129,7 @@ public interface CommandOption {
 	 */
 	public static CommandOption of(String[] longNames, Character[] shortNames, String description,
 			ResolvableType type) {
-		return of(longNames, shortNames, description, type, false, null, null, null, null, null);
+		return of(longNames, shortNames, description, type, false, null, null, null, null, null, null);
 	}
 
 	/**
@@ -133,13 +145,14 @@ public interface CommandOption {
 	 * @param arityMin the min arity
 	 * @param arityMax the max arity
 	 * @param label the label
+	 * @param completion the completion
 	 * @return default command option
 	 */
 	public static CommandOption of(String[] longNames, Character[] shortNames, String description,
 			ResolvableType type, boolean required, String defaultValue, Integer position, Integer arityMin,
-			Integer arityMax, String label) {
+			Integer arityMax, String label, Function<CompletionContext, List<CompletionProposal>> completion) {
 		return new DefaultCommandOption(longNames, shortNames, description, type, required, defaultValue, position,
-				arityMin, arityMax, label);
+				arityMin, arityMax, label, completion);
 	}
 
 	/**
@@ -157,10 +170,12 @@ public interface CommandOption {
 		private int arityMin;
 		private int arityMax;
 		private String label;
+		private Function<CompletionContext, List<CompletionProposal>> completion;
 
 		public DefaultCommandOption(String[] longNames, Character[] shortNames, String description,
 				ResolvableType type, boolean required, String defaultValue, Integer position,
-				Integer arityMin, Integer arityMax, String label) {
+				Integer arityMin, Integer arityMax, String label,
+				Function<CompletionContext, List<CompletionProposal>> completion) {
 			this.longNames = longNames != null ? longNames : new String[0];
 			this.shortNames = shortNames != null ? shortNames : new Character[0];
 			this.description = description;
@@ -171,6 +186,7 @@ public interface CommandOption {
 			this.arityMin = arityMin != null ? arityMin : -1;
 			this.arityMax = arityMax != null ? arityMax : -1;
 			this.label = label;
+			this.completion = completion;
 		}
 
 		@Override
@@ -222,5 +238,10 @@ public interface CommandOption {
 		public String getLabel() {
 			return label;
 		}
+
+		@Override
+		public Function<CompletionContext, List<CompletionProposal>> getCompletion() {
+			return completion;
+		}
 	}
 }

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

@@ -29,6 +29,8 @@ 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.context.InteractionMode;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
@@ -208,6 +210,14 @@ public interface CommandRegistration {
 		 */
 		OptionSpec label(String label);
 
+		/**
+		 * Define a {@code completion function} for an option.
+		 *
+		 * @param completion the completion function
+		 * @return option spec for chaining
+		 */
+		OptionSpec completion(Function<CompletionContext, List<CompletionProposal>> completion);
+
 		/**
 		 * Return a builder for chaining.
 		 *
@@ -528,6 +538,7 @@ public interface CommandRegistration {
 		private Integer arityMin;
 		private Integer arityMax;
 		private String label;
+		private Function<CompletionContext, List<CompletionProposal>> completion;
 
 		DefaultOptionSpec(BaseBuilder builder) {
 			this.builder = builder;
@@ -626,6 +637,12 @@ public interface CommandRegistration {
 			return this;
 		}
 
+		@Override
+		public OptionSpec completion(Function<CompletionContext, List<CompletionProposal>> completion) {
+			this.completion = completion;
+			return this;
+		}
+
 		@Override
 		public Builder and() {
 			return builder;
@@ -670,6 +687,10 @@ public interface CommandRegistration {
 		public String getLabel() {
 			return label;
 		}
+
+		public Function<CompletionContext, List<CompletionProposal>> getCompletion() {
+			return completion;
+		}
 	}
 
 	static class DefaultTargetSpec implements TargetSpec {
@@ -840,7 +861,7 @@ public interface CommandRegistration {
 			return optionSpecs.stream()
 				.map(o -> CommandOption.of(o.getLongNames(), o.getShortNames(), o.getDescription(), o.getType(),
 						o.isRequired(), o.getDefaultValue(), o.getPosition(), o.getArityMin(), o.getArityMax(),
-						o.getLabel()))
+						o.getLabel(), o.getCompletion()))
 				.collect(Collectors.toList());
 		}
 

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

@@ -224,37 +224,37 @@ public class ShellTests {
 		when(commandRegistry.getRegistrations()).thenReturn(registrations);
 
 		// Invoke at very start
-		List<String> proposals = shell.complete(new CompletionContext(Arrays.asList(""), 0, "".length()))
+		List<String> proposals = shell.complete(new CompletionContext(Arrays.asList(""), 0, "".length(), null, null))
 				.stream().map(CompletionProposal::value).collect(Collectors.toList());
 		assertThat(proposals).containsExactlyInAnyOrder("another command", "hello world");
 
 		// Invoke in middle of first word
-		proposals = shell.complete(new CompletionContext(Arrays.asList("hel"), 0, "hel".length()))
+		proposals = shell.complete(new CompletionContext(Arrays.asList("hel"), 0, "hel".length(), null, null))
 				.stream().map(CompletionProposal::value).collect(Collectors.toList());
 		assertThat(proposals).containsExactly("hello world");
 
 		// Invoke at end of first word (no space after yet)
-		proposals = shell.complete(new CompletionContext(Arrays.asList("hello"), 0, "hello".length()))
+		proposals = shell.complete(new CompletionContext(Arrays.asList("hello"), 0, "hello".length(), null, null))
 				.stream().map(CompletionProposal::value).collect(Collectors.toList());
 		assertThat(proposals).containsExactly("hello world");
 
 		// Invoke after first word / start of second word
-		proposals = shell.complete(new CompletionContext(Arrays.asList("hello", ""), 1, "".length()))
+		proposals = shell.complete(new CompletionContext(Arrays.asList("hello", ""), 1, "".length(), null, null))
 				.stream().map(CompletionProposal::value).collect(Collectors.toList());
 		assertThat(proposals).containsExactly("world");
 
 		// Invoke in middle of second word
-		proposals = shell.complete(new CompletionContext(Arrays.asList("hello", "wo"), 1, "wo".length()))
+		proposals = shell.complete(new CompletionContext(Arrays.asList("hello", "wo"), 1, "wo".length(), null, null))
 				.stream().map(CompletionProposal::value).collect(Collectors.toList());
 		assertThat(proposals).containsExactly("world");
 
 		// Invoke at end of whole command (no space after yet)
-		proposals = shell.complete(new CompletionContext(Arrays.asList("hello", "world"), 1, "world".length()))
+		proposals = shell.complete(new CompletionContext(Arrays.asList("hello", "world"), 1, "world".length(), null, null))
 				.stream().map(CompletionProposal::value).collect(Collectors.toList());
 		assertThat(proposals).containsExactly("world");
 
 		// Invoke in middle of second word
-		proposals = shell.complete(new CompletionContext(Arrays.asList("hello", "world", ""), 2, "".length()))
+		proposals = shell.complete(new CompletionContext(Arrays.asList("hello", "world", ""), 2, "".length(), null, null))
 				.stream().map(CompletionProposal::value).collect(Collectors.toList());
 		assertThat(proposals).isEmpty();
 	}
@@ -287,7 +287,7 @@ public class ShellTests {
 		registrations.put("hello world", registration1);
 		when(commandRegistry.getRegistrations()).thenReturn(registrations);
 
-		List<String> proposals = shell.complete(new CompletionContext(Arrays.asList("hello", "world", ""), 2, "".length()))
+		List<String> proposals = shell.complete(new CompletionContext(Arrays.asList("hello", "world", ""), 2, "".length(), null, null))
 				.stream().map(CompletionProposal::value).collect(Collectors.toList());
 		assertThat(proposals).containsExactlyInAnyOrder("--arg1");
 	}
@@ -311,7 +311,7 @@ public class ShellTests {
 		registrations.put("hello world", registration1);
 		when(commandRegistry.getRegistrations()).thenReturn(registrations);
 
-		List<String> proposals = shell.complete(new CompletionContext(Arrays.asList("hello", "world", ""), 2, "".length()))
+		List<String> proposals = shell.complete(new CompletionContext(Arrays.asList("hello", "world", ""), 2, "".length(), null, null))
 				.stream().map(CompletionProposal::value).collect(Collectors.toList());
 		assertThat(proposals).containsExactlyInAnyOrder("--arg1");
 	}

spring-shell-core/src/test/java/org/springframework/shell/command/CommandParserTests.java

@@ -327,7 +327,7 @@ public class CommandParserTests extends AbstractCommandTests {
 	public void testBooleanWithDefault() {
 		ResolvableType type = ResolvableType.forType(boolean.class);
 		CommandOption option1 = CommandOption.of(new String[] { "arg1" }, new Character[0], "description", type, false,
-				"true", null, null, null, null);
+				"true", null, null, null, null, null);
 
 		List<CommandOption> options = Arrays.asList(option1);
 		String[] args = new String[]{};
@@ -359,7 +359,7 @@ public class CommandParserTests extends AbstractCommandTests {
 
 	private static CommandOption longOption(String name, ResolvableType type, boolean required, Integer position, Integer arityMin, Integer arityMax) {
 		return CommandOption.of(new String[] { name }, new Character[0], "desc", type, required, null, position,
-				arityMin, arityMax, null);
+				arityMin, arityMax, null, null);
 	}
 
 	private static CommandOption shortOption(char name) {

spring-shell-core/src/test/java/org/springframework/shell/command/CommandRegistrationTests.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.shell.command;
 
+import java.util.ArrayList;
+
 import org.junit.jupiter.api.Test;
 
 import org.springframework.core.ResolvableType;
@@ -434,4 +436,23 @@ public class CommandRegistrationTests extends AbstractCommandTests {
 		assertThat(registration.getAvailability()).isNotNull();
 		assertThat(registration.getAvailability().isAvailable()).isFalse();
 	}
+
+	@Test
+	public void testOptionWithCompletion() {
+		CommandRegistration registration;
+		registration = CommandRegistration.builder()
+			.command("command1")
+			.withOption()
+				.longNames("arg1")
+				.completion(ctx -> {
+					return new ArrayList<>();
+				})
+				.and()
+			.withTarget()
+				.function(function1)
+				.and()
+			.build();
+		assertThat(registration.getOptions()).hasSize(1);
+		assertThat(registration.getOptions().get(0).getCompletion()).isNotNull();
+	}
 }