Attempt to reproduce issue #3618

querydsl-jpa/src/test/java/com/querydsl/jpa/JPQLSerializerTest.java

@@ -32,6 +32,8 @@
 import com.querydsl.jpa.domain.Location;
 import com.querydsl.jpa.domain.QDomesticCat;
 import com.querydsl.jpa.domain.QEmployee;
+import com.querydsl.jpa.domain.QUser;
+import com.querydsl.jpa.domain.UserRole;
 import java.util.Arrays;
 import org.junit.Test;
 
@@ -196,6 +198,24 @@ public void delete_with_subQuery() {
             """);
   }
 
+  @Test
+  public void where_in() {
+    QUser user = QUser.user;
+
+    JPQLSerializer serializer = new JPQLSerializer(HQLTemplates.DEFAULT);
+    QueryMetadata md = new DefaultQueryMetadata();
+    md.addJoin(JoinType.DEFAULT, user);
+    md.setProjection(user);
+    md.addWhere(user.roles.contains(UserRole.ADMIN));
+    serializer.serialize(md, false, null);
+    assertThat(serializer.toString())
+        .isEqualTo("""
+select user
+from User user
+where ?1 in user.roles
+""");
+  }
+
   @Test
   public void in() {
     JPQLSerializer serializer = new JPQLSerializer(HQLTemplates.DEFAULT);

querydsl-jpa/src/test/java/com/querydsl/jpa/domain/User.java

@@ -13,18 +13,25 @@
  */
 package com.querydsl.jpa.domain;
 
+import jakarta.persistence.Column;
+import jakarta.persistence.Convert;
 import jakarta.persistence.Entity;
 import jakarta.persistence.Id;
 import jakarta.persistence.ManyToOne;
 import jakarta.persistence.Table;
+import java.util.Set;
 
 /** The Class User. */
 @Entity
-@Table(name = "user_")
+@Table(name = "userc")
 public class User {
   @ManyToOne Company company;
 
   @Id long id;
 
   String userName, firstName, lastName;
+
+  @Convert(converter = UserRolesConverter.class)
+  @Column(columnDefinition = "TEXT")
+  Set<UserRole> roles;
 }

querydsl-jpa/src/test/java/com/querydsl/jpa/domain/UserRole.java

@@ -0,0 +1,8 @@
+package com.querydsl.jpa.domain;
+
+public enum UserRole {
+  ADMIN,
+  WRITER,
+  READER,
+  ANONYMOUS
+}

querydsl-jpa/src/test/java/com/querydsl/jpa/domain/UserRolesConverter.java

@@ -0,0 +1,25 @@
+package com.querydsl.jpa.domain;
+
+import jakarta.persistence.AttributeConverter;
+import java.util.Arrays;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+public class UserRolesConverter implements AttributeConverter<Set<UserRole>, String> {
+
+  @Override
+  public String convertToDatabaseColumn(Set<UserRole> roles) {
+    if (roles == null || roles.isEmpty()) return null;
+
+    return roles.stream().map(UserRole::name).collect(Collectors.joining(","));
+  }
+
+  @Override
+  public Set<UserRole> convertToEntityAttribute(String dbData) {
+    if (dbData == null || dbData.isEmpty()) {
+      return Set.of();
+    }
+
+    return Arrays.stream(dbData.split(",")).map(UserRole::valueOf).collect(Collectors.toSet());
+  }
+}