SHL-139: Handle escape sequences in option values

src/main/java/org/springframework/shell/core/Tokenizer.java

@@ -152,6 +152,10 @@ public class Tokenizer {
 		lastValueDelimiter = endDelimiter;
 		lastValueStartOffset = pos;
 		while (pos < buffer.length && buffer[pos] != endDelimiter) {
+			if (buffer[pos] == ESCAPE_CHAR) {
+				sb.append(processCharacterEscapeCodes(endDelimiter));
+				continue;
+			}
 			if (lookAhead(ESCAPE_CHAR, endDelimiter)) {
 				sb.append(endDelimiter);
 				pos += 2;
@@ -193,6 +197,59 @@ public class Tokenizer {
 		return sb.toString();
 	}
 
+	/**
+	 * When the escape character is encountered, consume and return the escaped sequence. Note that depending on which
+	 * end delimiter is currently in use, not all combinations need to be escaped
+	 * @param endDelimiter the current endDelimiter
+	 */
+	private char processCharacterEscapeCodes(char endDelimiter) {
+		pos++;
+		if (pos >= buffer.length) {
+			throw new IllegalArgumentException("Ran out of input in escape sequence");
+		}
+		switch (buffer[pos]) {
+		case ESCAPE_CHAR:
+			pos++; // consume the second escape char
+			return ESCAPE_CHAR;
+		case 't':
+			pos++;
+			return '\t';
+		case 'r':
+			pos++;
+			return '\r';
+		case 'n':
+			pos++;
+			return '\n';
+		case 'f':
+			pos++;
+			return '\f';
+		case 'u':
+			if (pos + 5 > buffer.length) {
+				throw new IllegalArgumentException("Ran out input in unicode escape sequence");
+			}
+			String hex = new String(buffer, pos + 1, 4);
+			try {
+				char code = (char) Integer.parseInt(hex, 16);
+				pos += 5;
+				return code;
+			}
+			catch (NumberFormatException e) {
+				throw new IllegalArgumentException("Illegal unicode escape sequence: " + ESCAPE_CHAR + "u" + hex);
+			}
+
+		default:
+			if (buffer[pos] == endDelimiter) {
+				pos++;
+				return endDelimiter;
+			}
+			else {
+				// Not an actual escape. Do not increment pos,
+				// and return the \ we consumed at the very beginning
+				return ESCAPE_CHAR;
+			}
+		}
+	}
+
 	/**
 	 * Return the offset at which the last value seen started (NOT including any delimiter).
 	 */
@@ -229,7 +286,12 @@ public class Tokenizer {
 	 * Apply delimiter escaping to the given string, using the actual delimiter that was used for the last value.
 	 */
 	public String escape(String value) {
-		return value.replace("" + lastValueDelimiter, "" + ESCAPE_CHAR + lastValueDelimiter);
+		String result = value.replace("" + lastValueDelimiter, "" + ESCAPE_CHAR + lastValueDelimiter);
+		result = result.replace("\r", "\\r");
+		result = result.replace("\n", "\\n");
+		result = result.replace("\t", "\\t");
+		result = result.replace("\f", "\\f");
+		return result;
 	}
 
 	/**

src/test/java/org/springframework/shell/core/TokenizerTests.java

@@ -24,6 +24,7 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -198,6 +199,21 @@ public class TokenizerTests {
 
 	}
 
+	@Test
+	public void testEscapeSequences() {
+		Map<String, String> result = tokenize("--foo \\t\\n\\r\\f");
+		assertEquals(Collections.singletonMap("foo", "\t\n\r\f"), result);
+
+		// Unicode and space-escape
+		result = tokenize("--foo \\u65e5\\ \\u672c");
+		assertEquals(Collections.singletonMap("foo", "\u65e5 \u672c"), result);
+
+		// backslash escape
+		result = tokenize("--foo \\\\u\\g");
+		assertEquals(Collections.singletonMap("foo", "\\u\\g"), result);
+
+	}
+
 	private Map<String, String> tokenize(String what) {
 		return new Tokenizer(what).getTokens();
 	}