Revisit posix short handling in Lexer

- Posix short style is expected to have only single
  dash and letters so use this style to come up better
  separation between options and arguments.
- Backport #1077
- Fixes #1079

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023 the original author or authors.
+ * Copyright 2023-2024 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.
@@ -201,12 +201,17 @@ public LexerResult tokenize(List<String> arguments) {
 					}
 				}
 				else if (isLastTokenOfType(tokenList, TokenType.OPTION)) {
-					if (argument.startsWith("-")) {
+					// posix short style can only have one or more letters
+					int decuceArgumentStyle = decuceArgumentStyle(argument);
+					if (decuceArgumentStyle > 0) {
 						tokenList.add(Token.of(argument, TokenType.OPTION, i2));
 					}
-					else {
+					else if (decuceArgumentStyle < 0) {
 						tokenList.add(Token.of(argument, TokenType.ARGUMENT, i2));
 					}
+					else {
+						tokenList.add(Token.of(argument, TokenType.OPTION, i2));
+					}
 				}
 				else if (isLastTokenOfType(tokenList, TokenType.COMMAND)) {
 					if (argument.startsWith("-")) {
@@ -243,5 +248,28 @@ private static boolean isLastTokenOfType(List<Token> tokenList, TokenType type)
 			}
 			return false;
 		}
+
+		private static int decuceArgumentStyle(String str) {
+			// positive - looks like posix short
+			// 0 - looks like long option
+			// negative - looks like argument, not option
+			if (str.length() < 2) {
+				return -1;
+			}
+			if (str.charAt(0) != '-') {
+				return -1;
+			}
+			if (str.length() > 1 && str.charAt(0) == '-' && str.charAt(1) == '-') {
+				return 0;
+			}
+			int ret = 1;
+			for (int i = 1; i < str.length(); i++) {
+				if (!Character.isLetter(str.charAt(i))) {
+					ret = -1;
+					break;
+				}
+			}
+			return ret;
+		}
 	}
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023 the original author or authors.
+ * Copyright 2023-2024 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.
@@ -19,6 +19,8 @@
 
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 import org.springframework.shell.command.parser.Lexer.LexerResult;
 import org.springframework.shell.command.parser.ParserConfig.Feature;
@@ -431,6 +433,42 @@ void commandArgsWithoutOption() {
 				TokenType.ARGUMENT);
 	}
 
+	@Nested
+	class ShortOptions {
+
+		@ParameterizedTest
+		@ValueSource(strings = {
+			"-1",
+			"-1a",
+			"-a1",
+			"-ab1",
+			"-ab1c"
+		})
+		void shouldNotBeOptionWhenDoesntLookLikeShortPosix(String arg) {
+			register(ROOT6_OPTION_INT);
+			List<Token> tokens = tokenize("root6", "--arg1", arg);
+
+			assertThat(tokens).extracting(Token::getType).containsExactly(TokenType.COMMAND, TokenType.OPTION,
+					TokenType.ARGUMENT);
+		}
+
+		@ParameterizedTest
+		@ValueSource(strings = {
+			"-a",
+			"-ab",
+			"-abc",
+			"--abc"
+		})
+		void shouldBeOptionWhenLooksLikeShortPosix(String arg) {
+			register(ROOT6_OPTION_INT);
+			List<Token> tokens = tokenize("root6", "--arg1", arg);
+
+			assertThat(tokens).extracting(Token::getType).containsExactly(TokenType.COMMAND, TokenType.OPTION,
+					TokenType.OPTION);
+		}
+	}
+
+
 	@Nested
 	class Directives {
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023 the original author or authors.
+ * Copyright 2023-2024 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.
@@ -116,6 +116,18 @@ void optionValueFailsFromStringToInteger() {
 				assertThat(ms.getMessage()).contains("Failed to convert");
 			});
 		}
+
+		@Test
+		void optionValueShouldBeNegativeInteger() {
+			register(ROOT6_OPTION_INT);
+			ParseResult result = parse("root6", "--arg1", "-1");
+			assertThat(result).isNotNull();
+			assertThat(result.commandRegistration()).isNotNull();
+			assertThat(result.optionResults()).isNotEmpty();
+			assertThat(result.optionResults().get(0).value()).isEqualTo(-1);
+			assertThat(result.messageResults()).isEmpty();
+		}
+
 	}
 
 	@Nested