Add Query alsoIf() to conditionally apply changes to a query

ebean-api/src/main/java/io/ebean/Query.java

@@ -11,6 +11,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
+import java.util.function.BooleanSupplier;
 import java.util.function.Consumer;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
@@ -671,6 +672,16 @@ public interface Query<T> extends CancelableQuery {
    */
   Query<T> apply(FetchPath fetchPath);
 
+  /**
+   * Apply changes to the query conditional on the supplied predicate.
+   * <p>
+   * Typically, the changes are extra predicates etc.
+   *
+   * @param predicate The predicate which when true the changes are applied
+   * @param apply The changes to apply to the query
+   */
+  Query<T> alsoIf(BooleanSupplier predicate, Consumer<Query<T>> apply);
+
   /**
    * Execute the query using the given transaction.
    */

ebean-core/src/main/java/io/ebeaninternal/server/query/DefaultFetchGroupQuery.java

@@ -37,6 +37,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
+import java.util.function.BooleanSupplier;
 import java.util.function.Consumer;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
@@ -219,6 +220,11 @@ final class DefaultFetchGroupQuery<T> implements SpiFetchGroupQuery<T>, SpiQuery
     throw new RuntimeException("EB102: Only select() and fetch() clause is allowed on FetchGroup");
   }
 
+  @Override
+  public Query<T> alsoIf(BooleanSupplier predicate, Consumer<Query<T>> apply) {
+    throw new RuntimeException("EB102: Only select() and fetch() clause is allowed on FetchGroup");
+  }
+
   @Override
   public Query<T> usingTransaction(Transaction transaction) {
     throw new RuntimeException("EB102: Only select() and fetch() clause is allowed on FetchGroup");

ebean-core/src/main/java/io/ebeaninternal/server/querydefn/DefaultOrmQuery.java

@@ -26,6 +26,7 @@ import javax.persistence.PersistenceException;
 import java.sql.Connection;
 import java.sql.Timestamp;
 import java.util.*;
+import java.util.function.BooleanSupplier;
 import java.util.function.Consumer;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
@@ -282,6 +283,14 @@ public class DefaultOrmQuery<T> extends AbstractQuery implements SpiQuery<T> {
     return this;
   }
 
+  @Override
+  public Query<T> alsoIf(BooleanSupplier predicate, Consumer<Query<T>> consumer) {
+    if (predicate.getAsBoolean()) {
+      consumer.accept(this);
+    }
+    return this;
+  }
+
   @Override
   public final void addSoftDeletePredicate(String softDeletePredicate) {
     if (softDeletePredicates == null) {

ebean-querybean/src/main/java/io/ebean/typequery/TQRootBean.java

@@ -16,6 +16,7 @@ import javax.sql.DataSource;
 import java.sql.Connection;
 import java.sql.Timestamp;
 import java.util.*;
+import java.util.function.BooleanSupplier;
 import java.util.function.Consumer;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
@@ -486,6 +487,21 @@ public abstract class TQRootBean<T, R> {
     return root;
   }
 
+  /**
+   * Apply changes to the query conditional on the supplied predicate.
+   * <p>
+   * Typically, the changes are extra predicates etc.
+   *
+   * @param predicate The predicate which when true the changes are applied
+   * @param apply The changes to apply to the query
+   */
+  public R alsoIf(BooleanSupplier predicate, Consumer<R> apply) {
+    if (predicate.getAsBoolean()) {
+      apply.accept(root);
+    }
+    return root;
+  }
+
   /**
    * Perform an 'As of' query using history tables to return the object graph
    * as of a time in the past.

ebean-querybean/src/test/java/org/querytest/QueryAlsoIfTest.java

@@ -0,0 +1,37 @@
+package org.querytest;
+
+import org.example.domain.Customer;
+import org.example.domain.query.QCustomer;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.example.domain.query.QCustomer.Alias.name;
+
+class QueryAlsoIfTest {
+
+  int dummy = 1;
+
+  @Test
+  void apply() {
+    var q = new QCustomer()
+      .select(name)
+      .name.isNotNull()
+      .alsoIf(() -> dummy == 1, query -> query.status.equalTo(Customer.Status.GOOD))
+      .query();
+
+    q.findList();
+    assertThat(q.getGeneratedSql()).isEqualTo("select t0.id, t0.name from be_customer t0 where t0.name is not null and t0.status = ?");
+  }
+
+  @Test
+  void notApply() {
+    var q = new QCustomer()
+      .select(name)
+      .name.isNotNull()
+      .alsoIf(() -> dummy > 1, query -> query.status.equalTo(Customer.Status.GOOD))
+      .query();
+
+    q.findList();
+    assertThat(q.getGeneratedSql()).isEqualTo("select t0.id, t0.name from be_customer t0 where t0.name is not null");
+  }
+}

ebean-test/src/test/java/org/tests/query/TestQueryAlsoIf.java

@@ -0,0 +1,36 @@
+package org.tests.query;
+
+import io.ebean.DB;
+import io.ebean.Query;
+import org.junit.jupiter.api.Test;
+import org.tests.model.basic.Customer;
+import org.tests.model.basic.ResetBasicData;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class TestQueryAlsoIf {
+
+  int dummy = 1;
+
+  @Test
+  void apply() {
+    ResetBasicData.reset();
+    Query<Customer> query = DB.find(Customer.class)
+      .select("name")
+      .alsoIf(() -> dummy == 1, qy -> qy.where().isNotNull("name"));
+
+    query.findList();
+    assertThat(query.getGeneratedSql()).isEqualTo("select t0.id, t0.name from o_customer t0 where t0.name is not null");
+  }
+
+  @Test
+  void notApply() {
+    ResetBasicData.reset();
+    Query<Customer> query = DB.find(Customer.class)
+      .select("name")
+      .alsoIf(() -> dummy > 1, qy -> qy.where().isNotNull("name"));
+
+    query.findList();
+    assertThat(query.getGeneratedSql()).isEqualTo("select t0.id, t0.name from o_customer t0");
+  }
+}