Document support for varargs invocations in SpEL

Closes gh-33332

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

@@ -21,10 +21,13 @@ import java.lang.invoke.MethodHandles;
 import java.lang.invoke.MethodType;
 import java.lang.reflect.Method;
 import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
 import java.util.Date;
 import java.util.GregorianCalendar;
 import java.util.List;
 import java.util.Map;
+import java.util.stream.Collectors;
 
 import example.Color;
 import example.FruitMap;
@@ -667,6 +670,59 @@ class SpelDocumentationTests extends AbstractExpressionTests {
 		}
 	}
 
+	@Nested
+	class Varargs {
+
+		@Test
+		void varargsMethodInvocationWithIndividualArguments() {
+			// evaluates to "blue is color #1"
+			String expression = "'%s is color #%d'.formatted('blue', 1)";
+			String message = parser.parseExpression(expression)
+					.getValue(String.class);
+			assertThat(message).isEqualTo("blue is color #1");
+		}
+
+		@Test
+		void varargsMethodInvocationWithArgumentsAsObjectArray() {
+			// evaluates to "blue is color #1"
+			String expression = "'%s is color #%d'.formatted(new Object[] {'blue', 1})";
+			String message = parser.parseExpression(expression)
+					.getValue(String.class);
+			assertThat(message).isEqualTo("blue is color #1");
+		}
+
+		@Test
+		void varargsMethodInvocationWithArgumentsAsInlineList() {
+			// evaluates to "blue is color #1"
+			String expression = "'%s is color #%d'.formatted({'blue', 1})";
+			String message = parser.parseExpression(expression).getValue(String.class);
+			assertThat(message).isEqualTo("blue is color #1");
+		}
+
+		@Test
+		void varargsMethodInvocationWithTypeConversion() {
+			Method reverseStringsMethod = ReflectionUtils.findMethod(StringUtils.class, "reverseStrings", String[].class);
+			SimpleEvaluationContext evaluationContext = SimpleEvaluationContext.forReadOnlyDataBinding().build();
+			evaluationContext.setVariable("reverseStrings", reverseStringsMethod);
+
+			// String reverseStrings(String... strings)
+			// evaluates to "3.0, 2.0, 1.0, SpEL"
+			String expression = "#reverseStrings('SpEL', 1, 10F / 5, 3.0000)";
+			String message = parser.parseExpression(expression)
+					.getValue(evaluationContext, String.class);
+			assertThat(message).isEqualTo("3.0, 2.0, 1, SpEL");
+		}
+
+		@Test
+		void varargsMethodInvocationWithArgumentsAsStringArray() {
+			// evaluates to "blue is color #1"
+			String expression = "'%s is color #%s'.formatted(new String[] {'blue', 1})";
+			String message = parser.parseExpression(expression).getValue(String.class);
+			assertThat(message).isEqualTo("blue is color #1");
+		}
+
+	}
+
 	@Nested
 	class TernaryOperator {
 
@@ -906,6 +962,12 @@ class SpelDocumentationTests extends AbstractExpressionTests {
 		public static String reverseString(String input) {
 			return new StringBuilder(input).reverse().toString();
 		}
+
+		public static String reverseStrings(String... strings) {
+			List<String> list = Arrays.asList(strings);
+			Collections.reverse(list);
+			return list.stream().collect(Collectors.joining(", "));
+		}
 	}
 
 	private static class ListConcatenation implements OperatorOverloader {