Fix double parentheses in IN predicate rendering

Prevent duplicate parentheses when rendering IN/NOT IN predicates
with expressions that already contain parentheses. Added logic to
check if predicate string starts and ends with parentheses before
wrapping with additional parentheses.

This change improves JPQL query readability by avoiding patterns
like "field IN (('value1', 'value2'))" and ensures proper syntax
for subqueries and already-parenthesized expressions.

Added comprehensive unit tests to verify the fix handles various
scenarios including regular expressions, pre-parenthesized
expressions, and subquery expressions.

Signed-off-by: Choi Wang Gyu <dhkdrb897@gmail.com>

Author: cwangg897

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/JpqlQueryBuilder.java

@@ -44,6 +44,7 @@
  * A Domain-Specific Language to build JPQL queries using Java code.
  *
  * @author Mark Paluch
+ * @author Choi Wang Gyu
  */
 @SuppressWarnings("JavadocDeclaration")
 public final class JpqlQueryBuilder {
@@ -1422,8 +1423,14 @@ record InPredicate(Expression path, String operator, Expression predicate) imple
 		@Override
 		public String render(RenderContext context) {
 
-			// TODO: should we rather wrap it with nested or check if its a nested predicate before we call render
-			return "%s %s (%s)".formatted(path.render(context), operator, predicate.render(context));
+			String predicateStr = predicate.render(context);
+			
+			// Avoid double parentheses if predicate string already starts and ends with parentheses
+			if (predicateStr.startsWith("(") && predicateStr.endsWith(")")) {
+				return "%s %s %s".formatted(path.render(context), operator, predicateStr);
+			}
+			
+			return "%s %s (%s)".formatted(path.render(context), operator, predicateStr);
 		}
 
 		@Override

spring-data-jpa/src/test/java/org/springframework/data/jpa/repository/query/JpqlQueryBuilderUnitTests.java

@@ -34,6 +34,7 @@
  *
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Choi Wang Gyu
  */
 class JpqlQueryBuilderUnitTests {
 
@@ -136,6 +137,31 @@ void predicateRendering() {
 		assertThat(where.neq(expression("'AT'")).render(context)).isEqualTo("o.country != 'AT'");
 	}
 
+	@Test // GH-3961 - Nested predicate parentheses handling
+	void inPredicateWithNestedExpression() {
+
+		Entity entity = JpqlQueryBuilder.entity(Order.class);
+		WhereStep where = JpqlQueryBuilder.where(JpqlQueryBuilder.path(entity, "country"));
+		RenderContext context = ctx(entity);
+
+		// Test regular IN predicate with parentheses
+		assertThat(where.in(expression("'AT', 'DE'")).render(context)).isEqualTo("o.country IN ('AT', 'DE')");
+
+		// Test IN predicate with already parenthesized expression - should avoid double parentheses
+		Expression parenthesizedExpression = expression("('AT', 'DE')");
+		assertThat(where.in(parenthesizedExpression).render(context))
+				.isEqualTo("o.country IN ('AT', 'DE')");
+
+		// Test NOT IN predicate with already parenthesized expression
+		assertThat(where.notIn(parenthesizedExpression).render(context))
+				.isEqualTo("o.country NOT IN ('AT', 'DE')");
+
+		// Test IN with subquery (already parenthesized)
+		Expression subqueryExpression = expression("(SELECT c.code FROM Country c WHERE c.active = true)");
+		assertThat(where.in(subqueryExpression).render(context))
+				.isEqualTo("o.country IN (SELECT c.code FROM Country c WHERE c.active = true)");
+	}
+
 	@Test // GH-3588
 	void selectRendering() {