Merge pull request #49152 from osvetlik

* pr/49152:
  Polish "Bind `Optional` value object parameters as empty rather than `null`"
  Bind `Optional` value object parameters as empty rather than `null`

Closes gh-49152

core/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/BindConverter.java

@@ -98,14 +98,12 @@ final class BindConverter {
 
 	@SuppressWarnings("unchecked")
 	<T> @Nullable T convert(@Nullable Object source, ResolvableType targetType, Annotation... targetAnnotations) {
-		if (source == null) {
-			return null;
-		}
-		return (T) convert(source, TypeDescriptor.forObject(source),
-				new ResolvableTypeDescriptor(targetType, targetAnnotations));
+		TypeDescriptor sourceType = (source != null) ? TypeDescriptor.forObject(source) : null;
+		return (T) convert(source, sourceType, new ResolvableTypeDescriptor(targetType, targetAnnotations));
 	}
 
-	private @Nullable Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+	private @Nullable Object convert(@Nullable Object source, @Nullable TypeDescriptor sourceType,
+			TypeDescriptor targetType) {
 		ConversionException failure = null;
 		for (ConversionService delegate : this.delegates) {
 			try {
@@ -119,6 +117,9 @@ final class BindConverter {
 				}
 			}
 		}
+		if (source == null) {
+			return null;
+		}
 		throw (failure != null) ? failure : new ConverterNotFoundException(sourceType, targetType);
 	}
 

core/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/ValueObjectBinder.java

@@ -61,6 +61,7 @@ import org.springframework.util.Assert;
  * @author Stephane Nicoll
  * @author Phillip Webb
  * @author Scott Frederick
+ * @author Ondřej Světlík
  */
 class ValueObjectBinder implements DataObjectBinder {
 
@@ -132,7 +133,7 @@ class ValueObjectBinder implements DataObjectBinder {
 				return convertDefaultValue(context.getConverter(), defaultValue, type, annotations);
 			}
 		}
-		return null;
+		return context.getConverter().convert(null, type);
 	}
 
 	private <T> @Nullable T convertDefaultValue(BindConverter converter, String[] defaultValue, ResolvableType type,

core/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/ValueObjectBinderTests.java

@@ -50,6 +50,7 @@ import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
  * @author Phillip Webb
  * @author Pavel Anisimov
  * @author Yanming Zhou
+ * @author Ondřej Světlík
  */
 class ValueObjectBinderTests {
 
@@ -326,6 +327,25 @@ class ValueObjectBinderTests {
 		assertThat(bound.getOptionalValue()).isEmpty();
 	}
 
+	@Test
+	void bindWhenOptionalParameterWithNoValueForPrimitiveShouldReturnEmptyInstance() {
+		RecordPropertiesWithOptional bound = this.binder.bindOrCreate("foo",
+				Bindable.of(RecordPropertiesWithOptional.class));
+		assertThat(bound.property1()).isEmpty();
+	}
+
+	@Test
+	void bindWhenOptionalParameterInNestedWithNoValueForPrimitiveShouldReturnEmptyInstance() {
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("foo.nested.property2", "str");
+		this.sources.add(source);
+		RecordPropertiesWithOptionalInNestedRecord bound = this.binder.bindOrCreate("foo",
+				Bindable.of(RecordPropertiesWithOptionalInNestedRecord.class));
+		assertThat(bound.nested()).isNotNull();
+		assertThat(bound.nested().property1()).isNotNull().isEmpty();
+		assertThat(bound.nested().property2()).isEqualTo("str");
+	}
+
 	@Test
 	void bindWhenEnumParameterWithEmptyDefaultValueShouldThrowException() {
 		assertThatExceptionOfType(BindException.class)
@@ -902,6 +922,14 @@ class ValueObjectBinderTests {
 			@DefaultValue("default-value-2") String property2) {
 	}
 
+	record RecordPropertiesWithOptional(Optional<String> property1) {
+	}
+
+	record RecordPropertiesWithOptionalInNestedRecord(NestedRecord nested) {
+		record NestedRecord(Optional<String> property1, String property2) {
+		}
+	}
+
 	static class NonExtractableParameterName {
 
 		private @Nullable String value;