Querydsl does not allow `null` predicate for `findAll()`

core/pom.xml

@@ -39,6 +39,8 @@
 				<version>1.1.3</version>
 				<executions>
 					<execution>
+						<id>generate-source-entities</id>
+						<phase>generate-sources</phase>
 						<goals>
 							<goal>process</goal>
 						</goals>
@@ -51,6 +53,21 @@
 							<processor>com.querydsl.apt.jpa.JPAAnnotationProcessor</processor>
 						</configuration>
 					</execution>
+					<execution>
+						<id>generate-test-entities</id>
+						<phase>generate-test-sources</phase>
+						<goals>
+							<goal>test-process</goal>
+						</goals>
+						<configuration>
+							<includes>
+								<!-- List packages to be processed -->
+								<include>org.genesys.blocks.model</include>
+							</includes>
+							<outputDirectory>target/generated-test-sources/querydsl</outputDirectory>
+							<processor>com.querydsl.apt.jpa.JPAAnnotationProcessor</processor>
+						</configuration>
+					</execution>
 				</executions>
 				<dependencies>
 					<dependency>

core/src/main/java/org/genesys/blocks/model/filters/SuperModelFilter.java

@@ -39,6 +39,7 @@ import com.fasterxml.jackson.databind.SerializerProvider;
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
 import com.fasterxml.jackson.databind.annotation.JsonSerialize;
 import com.fasterxml.jackson.databind.deser.ContextualDeserializer;
+import com.querydsl.core.BooleanBuilder;
 import com.querydsl.core.types.ExpressionUtils;
 import com.querydsl.core.types.Predicate;
 import com.querydsl.core.types.dsl.CollectionPathBase;
@@ -84,7 +85,8 @@ public abstract class SuperModelFilter<T extends SuperModelFilter<T, R>, R> {
 	 * @return the predicate
 	 */
 	public Predicate buildPredicate() {
-		return ExpressionUtils.allOf(collectPredicates());
+		Predicate collected = ExpressionUtils.allOf(collectPredicates());
+		return collected == null ? new BooleanBuilder() : collected;
 	}
 
 	/**

core/src/test/java/org/genesys/blocks/model/VersionedEntityFilter.java

+/*
+ * Copyright 2020 Global Crop Diversity Trust
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.genesys.blocks.model;
+
+import java.util.List;
+
+import org.genesys.blocks.model.filters.StringFilter;
+import org.genesys.blocks.model.filters.VersionedModelFilter;
+
+import com.querydsl.core.types.Predicate;
+
+public class VersionedEntityFilter extends VersionedModelFilter<VersionedEntityFilter, VersionedEntity> {
+
+	public StringFilter name;
+	
+	public List<Predicate> collectPredicates() {
+		return collectPredicates(QVersionedEntity.versionedEntity);
+	}
+	
+	public List<Predicate> collectPredicates(QVersionedEntity versionedEntity) {
+		final List<Predicate> predicates = super.collectPredicates(versionedEntity, versionedEntity._super._super);
+		
+		if (name != null) {
+			predicates.add(name.buildQuery(versionedEntity.name));
+		}
+		
+		return predicates;
+	}
+}

core/src/test/java/org/genesys/blocks/persistence/VersionedEntityRepository.java

@@ -17,10 +17,11 @@ package org.genesys.blocks.persistence;
 
 import org.genesys.blocks.model.VersionedEntity;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.querydsl.QuerydslPredicateExecutor;
 
 /**
  * The Interface VersionedEntityRepository.
  */
-public interface VersionedEntityRepository extends JpaRepository<VersionedEntity, Long> {
+public interface VersionedEntityRepository extends JpaRepository<VersionedEntity, Long>, QuerydslPredicateExecutor<VersionedEntity> {
 
 }

core/src/test/java/org/genesys/blocks/tests/model/VersionedModelTest.java

@@ -15,14 +15,15 @@
  */
 package org.genesys.blocks.tests.model;
 
-import static org.hamcrest.Matchers.not;
-import static org.hamcrest.Matchers.is;
-import static org.hamcrest.Matchers.nullValue;
-import static org.junit.Assert.assertThat;
+import static org.hamcrest.Matchers.*;
+import static org.junit.Assert.*;
 
 import org.genesys.blocks.model.VersionedEntity;
+import org.genesys.blocks.model.VersionedEntityFilter;
 import org.genesys.blocks.tests.ServiceTest;
 import org.junit.Test;
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.PageRequest;
 import org.springframework.transaction.annotation.Transactional;
 
 /**
@@ -75,6 +76,26 @@ public class VersionedModelTest extends ServiceTest {
 		assertThat(entity.isActive(), is(false));
 	}
 
+	@Test
+	public void testEmptyFilter() {
+		VersionedEntityFilter filter = new VersionedEntityFilter();
+		Page<VersionedEntity> page = versionedEntityRepository.findAll(filter.buildPredicate(), PageRequest.of(0, 10));
+		assertThat(page, not(nullValue()));
+	}
+	
+	@Test
+	public void testStringFilter() {
+		VersionedEntity entity = versionedEntityRepository.save(createEntity());
+
+		VersionedEntityFilter filter = new VersionedEntityFilter();
+		filter.id().add(entity.getId());
+
+		Page<VersionedEntity> page = versionedEntityRepository.findAll(filter.buildPredicate(), PageRequest.of(0, 10));
+		assertThat(page, not(nullValue()));
+		assertThat(page.getContent().size(), is(1));
+		assertThat(page.getContent().get(0), is(entity));
+	}
+	
 	/**
 	 * Creates the entity.
 	 *