Polishing.

Add fix to Update, Delete, and PredicateSpecification. Reformat code. Refine tests.

See #3849
Original pull request: #3856

Author: mp911de

spring-data-jpa/src/main/java/org/springframework/data/jpa/domain/DeleteSpecification.java

@@ -24,9 +24,9 @@
 import java.util.Arrays;
 import java.util.stream.StreamSupport;
 
-import org.springframework.lang.CheckReturnValue;
-
 import org.jspecify.annotations.Nullable;
+
+import org.springframework.lang.CheckReturnValue;
 import org.springframework.lang.Contract;
 import org.springframework.util.Assert;
 
@@ -159,7 +159,7 @@ static <T> DeleteSpecification<T> not(DeleteSpecification<T> spec) {
 		return (root, delete, builder) -> {
 
 			Predicate predicate = spec.toPredicate(root, delete, builder);
-			return predicate != null ? builder.not(predicate) : null;
+			return predicate != null ? builder.not(predicate) : builder.disjunction();
 		};
 	}
 

spring-data-jpa/src/main/java/org/springframework/data/jpa/domain/PredicateSpecification.java

@@ -23,9 +23,9 @@
 import java.util.Arrays;
 import java.util.stream.StreamSupport;
 
-import org.springframework.lang.CheckReturnValue;
-
 import org.jspecify.annotations.Nullable;
+
+import org.springframework.lang.CheckReturnValue;
 import org.springframework.lang.Contract;
 import org.springframework.util.Assert;
 
@@ -113,7 +113,7 @@ static <T> PredicateSpecification<T> not(PredicateSpecification<T> spec) {
 		return (root, builder) -> {
 
 			Predicate predicate = spec.toPredicate(root, builder);
-			return predicate != null ? builder.not(predicate) : null;
+			return predicate != null ? builder.not(predicate) : builder.disjunction();
 		};
 	}
 

spring-data-jpa/src/main/java/org/springframework/data/jpa/domain/UpdateSpecification.java

@@ -24,9 +24,9 @@
 import java.util.Arrays;
 import java.util.stream.StreamSupport;
 
-import org.springframework.lang.CheckReturnValue;
-
 import org.jspecify.annotations.Nullable;
+
+import org.springframework.lang.CheckReturnValue;
 import org.springframework.lang.Contract;
 import org.springframework.util.Assert;
 
@@ -180,7 +180,7 @@ static <T> UpdateSpecification<T> not(UpdateSpecification<T> spec) {
 		return (root, update, builder) -> {
 
 			Predicate predicate = spec.toPredicate(root, update, builder);
-			return predicate != null ? builder.not(predicate) : null;
+			return predicate != null ? builder.not(predicate) : builder.disjunction();
 		};
 	}
 

spring-data-jpa/src/test/java/org/springframework/data/jpa/domain/DeleteSpecificationUnitTests.java

@@ -160,6 +160,17 @@ void orCombinesSpecificationsInOrder() {
 		verify(builder).or(firstPredicate, secondPredicate);
 	}
 
+	@Test // GH-3849
+	void notWithNullPredicate() {
+
+		when(builder.disjunction()).thenReturn(mock(Predicate.class));
+
+		DeleteSpecification<Object> notSpec = DeleteSpecification.not((r, q, cb) -> null);
+
+		assertThat(notSpec.toPredicate(root, delete, builder)).isNotNull();
+		verify(builder).disjunction();
+	}
+
 	static class SerializableSpecification implements Serializable, DeleteSpecification<Object> {
 
 		@Override

spring-data-jpa/src/test/java/org/springframework/data/jpa/domain/PredicateSpecificationUnitTests.java

@@ -158,6 +158,17 @@ void orCombinesSpecificationsInOrder() {
 		verify(builder).or(firstPredicate, secondPredicate);
 	}
 
+	@Test // GH-3849
+	void notWithNullPredicate() {
+
+		when(builder.disjunction()).thenReturn(mock(Predicate.class));
+
+		PredicateSpecification<Object> notSpec = PredicateSpecification.not((r, cb) -> null);
+
+		assertThat(notSpec.toPredicate(root, builder)).isNotNull();
+		verify(builder).disjunction();
+	}
+
 	static class SerializableSpecification implements Serializable, PredicateSpecification<Object> {
 
 		@Override

spring-data-jpa/src/test/java/org/springframework/data/jpa/domain/UpdateSpecificationUnitTests.java

@@ -160,6 +160,17 @@ void orCombinesSpecificationsInOrder() {
 		verify(builder).or(firstPredicate, secondPredicate);
 	}
 
+	@Test // GH-3849
+	void notWithNullPredicate() {
+
+		when(builder.disjunction()).thenReturn(mock(Predicate.class));
+
+		UpdateSpecification<Object> notSpec = UpdateSpecification.not((r, q, cb) -> null);
+
+		assertThat(notSpec.toPredicate(root, update, builder)).isNotNull();
+		verify(builder).disjunction();
+	}
+
 	static class SerializableSpecification implements Serializable, UpdateSpecification<Object> {
 
 		@Override