Improve diagnostics in SpEL for repeated text

Attempting to create repeated text in a SpEL expression using the
repeat operator can result in errors that are not very helpful to the
user.

This commit improves the diagnostics in SpEL for the repeat operator by
throwing a SpelEvaluationException with a meaningful error message in
order to better assist the user.

Closes gh-30149

spring-expression/src/test/java/org/springframework/expression/spel/OperatorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -21,10 +21,12 @@ import java.math.BigInteger;
 
 import org.junit.jupiter.api.Test;
 
+import org.springframework.expression.Expression;
 import org.springframework.expression.spel.ast.Operator;
 import org.springframework.expression.spel.standard.SpelExpression;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.expression.spel.SpelMessage.MAX_REPEATED_TEXT_SIZE_EXCEEDED;
 
 /**
  * Tests the evaluation of expressions using relational operators.
@@ -32,6 +34,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * @author Andy Clement
  * @author Juergen Hoeller
  * @author Giovanni Dall'Oglio Risso
+ * @author Sam Brannen
  */
 public class OperatorTests extends AbstractExpressionTests {
 
@@ -324,11 +327,6 @@ public class OperatorTests extends AbstractExpressionTests {
 		evaluate("3.5", 3.5d, Double.class);
 	}
 
-	@Test
-	public void testMultiplyStringInt() {
-		evaluate("'a' * 5", "aaaaa", String.class);
-	}
-
 	@Test
 	public void testMultiplyDoubleDoubleGivesDouble() {
 		evaluate("3.0d * 5.0d", 15.0d, Double.class);
@@ -576,6 +574,19 @@ public class OperatorTests extends AbstractExpressionTests {
 		evaluate("'abc' != 'def'", true, Boolean.class);
 	}
 
+	@Test
+	void stringRepeat() {
+		evaluate("'abc' * 0", "", String.class);
+		evaluate("'abc' * 1", "abc", String.class);
+		evaluate("'abc' * 2", "abcabc", String.class);
+
+		Expression expr = parser.parseExpression("'a' * 256");
+		assertThat(expr.getValue(context, String.class)).hasSize(256);
+
+		// 4 is the position of the '*' (repeat operator)
+		evaluateAndCheckError("'a' * 257", String.class, MAX_REPEATED_TEXT_SIZE_EXCEEDED, 4);
+	}
+
 	@Test
 	public void testLongs() {
 		evaluate("3L == 4L", false, Boolean.class);