Rework command parser

- Previously CommandParser contained parser which was
  scannerless type of brute force parsing of command
  line args.
- Contract in that old parser wasn't super clear what
  is its role with caller as it was given options
  and registration was parsed in a Shell class.
- Add completely new parser package which has better
  model and which will be much easier to modify for
  future needs.
- Change some interfaces around parsing so that we do
  as much in this new parsing model instead of pre-parsing
  something in a Shell class.
- We also try to move away from using exceptions as
  a message delivery which had its own problems. Instead
  introducing parser messages which gives better info
  when errors are detected.
- Add ParserConfig class which allows to expose settings
  to change some parser features. Later this will be
  exposed to user so that some features can be turned on/off
  for an actual shell needs.
- Fixes #646

Author: jvalkeal

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

@@ -229,8 +229,6 @@ protected Object evaluate(Input input) {
 			this.exitCodeMappings.reset(mappingFunctions);
 		}
 
-		List<String> wordsForArgs = wordsForArguments(command, words);
-
 		Thread commandThread = Thread.currentThread();
 		Object sh = Signals.register("INT", () -> commandThread.interrupt());
 
@@ -243,7 +241,7 @@ protected Object evaluate(Input input) {
 		Object evaluate = null;
 		Exception e = null;
 		try {
-			evaluate = execution.evaluate(commandRegistration.get(), wordsForArgs.toArray(new String[0]));
+			evaluate = execution.evaluate(words.toArray(new String[0]));
 		}
 		catch (UndeclaredThrowableException ute) {
 			if (ute.getCause() instanceof InterruptedException || ute.getCause() instanceof ClosedByInterruptException) {
@@ -327,21 +325,6 @@ private boolean noInput(Input input) {
 				|| (input.words().iterator().next().matches("\\s*//.*"));
 	}
 
-	/**
-	 * Returns the list of words to be considered for argument resolving. Drops the first N
-	 * words used for the command, as well as an optional empty word at the end of the list
-	 * (which may be present if user added spaces before submitting the buffer)
-	 */
-	private List<String> wordsForArguments(String command, List<String> words) {
-		int wordsUsedForCommandKey = command.split(" ").length;
-		List<String> args = words.subList(wordsUsedForCommandKey, words.size());
-		int last = args.size() - 1;
-		if (last >= 0 && "".equals(args.get(last))) {
-			args.remove(last);
-		}
-		return args;
-	}
-
 	/**
 	 * Gather completion proposals given some (incomplete) input the user has already typed
 	 * in. When and how this method is invoked is implementation specific and decided by the

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 the original author or authors.
+ * Copyright 2022-2023 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.
@@ -38,6 +38,7 @@
 import org.springframework.shell.command.CommandRegistration.TargetInfo.TargetType;
 import org.springframework.shell.command.invocation.InvocableShellMethod;
 import org.springframework.shell.command.invocation.ShellMethodArgumentResolverComposite;
+import org.springframework.shell.command.parser.ParserConfig;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -50,11 +51,10 @@ public interface CommandExecution {
 	/**
 	 * Evaluate a command with a given arguments.
 	 *
-	 * @param registration the command registration
 	 * @param args         the command args
 	 * @return evaluated execution
 	 */
-	Object evaluate(CommandRegistration registration, String[] args);
+	Object evaluate(String[] args);
 
 	/**
 	 * Gets an instance of a default {@link CommandExecution}.
@@ -114,17 +114,17 @@ public DefaultCommandExecution(List<? extends HandlerMethodArgumentResolver> res
 			this.commandCatalog = commandCatalog;
 		}
 
-		public Object evaluate(CommandRegistration registration, String[] args) {
+		public Object evaluate(String[] args) {
+			CommandParser parser = CommandParser.of(conversionService, commandCatalog.getRegistrations(), new ParserConfig());
+			CommandParserResults results = parser.parse(args);
+			CommandRegistration registration = results.registration();
+
 			// fast fail with availability before doing anything else
 			Availability availability = registration.getAvailability();
 			if (availability != null && !availability.isAvailable()) {
 				return new CommandNotCurrentlyAvailable(registration.getCommand(), availability);
 			}
 
-			List<CommandOption> options = registration.getOptions();
-			CommandParser parser = CommandParser.of(conversionService);
-			CommandParserResults results = parser.parse(options, args);
-
 			// check help options to short circuit
 			boolean handleHelpOption = false;
 			HelpOptionInfo helpOption = registration.getHelpOption();
@@ -157,11 +157,11 @@ public Object evaluate(CommandRegistration registration, String[] args) {
 			CommandRegistration usedRegistration;
 			if (handleHelpOption) {
 				String command = registration.getCommand();
-				CommandParser helpParser = CommandParser.of(conversionService);
+				CommandParser helpParser = CommandParser.of(conversionService, commandCatalog.getRegistrations(),
+						new ParserConfig());
 				CommandRegistration helpCommandRegistration = commandCatalog.getRegistrations()
 						.get(registration.getHelpOption().getCommand());
-				List<CommandOption> helpOptions = helpCommandRegistration.getOptions();
-				CommandParserResults helpResults = helpParser.parse(helpOptions, new String[] { "--command", command });
+				CommandParserResults helpResults = helpParser.parse(new String[] { "help", "--command", command });
 				results = helpResults;
 				usedRegistration = helpCommandRegistration;
 			}