Ignore nested with NoUnboundElementsBindHandler

Update `NoUnboundElementsBindHandler` to also support ignoring
nested properties. This change is required to allow the
`NoUnboundElementsBindHandler` to be used alongside the
`IgnoreNestedPropertiesBindHandler`.

See gh-9000

spring-boot/src/main/java/org/springframework/boot/context/properties/ConfigurationPropertiesBindingPostProcessor.java

@@ -411,7 +411,8 @@ public class ConfigurationPropertiesBindingPostProcessor implements BeanPostProc
 			handler = new IgnoreErrorsBindHandler(handler);
 		}
 		if (!annotation.ignoreUnknownFields()) {
-			handler = new NoUnboundElementsBindHandler(handler);
+			handler = new NoUnboundElementsBindHandler(handler,
+					annotation.ignoreNestedProperties());
 		}
 		if (annotation.ignoreNestedProperties()) {
 			handler = new IgnoreNestedPropertiesBindHandler(handler);

spring-boot/src/main/java/org/springframework/boot/context/properties/bind/handler/NoUnboundElementsBindHandler.java

@@ -40,14 +40,28 @@ import org.springframework.boot.context.properties.source.IterableConfigurationP
  */
 public class NoUnboundElementsBindHandler extends AbstractBindHandler {
 
+	private final boolean ignoreNested;
+
 	private final Set<ConfigurationPropertyName> boundNames = new HashSet<>();
 
 	public NoUnboundElementsBindHandler() {
 		super();
+		this.ignoreNested = false;
+	}
+
+	public NoUnboundElementsBindHandler(boolean ignoreNested) {
+		super();
+		this.ignoreNested = ignoreNested;
 	}
 
 	public NoUnboundElementsBindHandler(BindHandler parent) {
 		super(parent);
+		this.ignoreNested = false;
+	}
+
+	public NoUnboundElementsBindHandler(BindHandler parent, boolean ignoreNested) {
+		super(parent);
+		this.ignoreNested = ignoreNested;
 	}
 
 	@Override
@@ -96,7 +110,11 @@ public class NoUnboundElementsBindHandler extends AbstractBindHandler {
 
 	private boolean isUnbound(ConfigurationPropertyName name,
 			ConfigurationPropertyName candidate) {
-		return name.isAncestorOf(candidate) && !this.boundNames.contains(candidate);
+		boolean isParent = candidate.getParent() != null
+				&& name.equals(candidate.getParent());
+		boolean isAncestor = name.isAncestorOf(candidate);
+		return ((this.ignoreNested ? isParent : isAncestor)
+				&& !this.boundNames.contains(candidate));
 	}
 
 }

spring-boot/src/test/java/org/springframework/boot/context/properties/bind/handler/NoUnboundElementsBindHandlerTests.java

@@ -103,6 +103,37 @@ public class NoUnboundElementsBindHandlerTests {
 		assertThat(bound.getFoo()).isEqualTo("bar");
 	}
 
+	@Test
+	public void bindWhenUsingNoUnboundElementsHandlerIgnoreNestedAndUnboundChildShouldThrowException()
+			throws Exception {
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("example.foo", "bar");
+		source.put("example.baz", "bar");
+		this.sources.add(source);
+		this.binder = new Binder(this.sources);
+		try {
+			this.binder.bind("example", Bindable.of(Example.class),
+					new NoUnboundElementsBindHandler(true));
+			fail("did not throw");
+		}
+		catch (BindException ex) {
+			assertThat(ex.getCause().getMessage())
+					.contains("The elements [example.baz] were left unbound");
+		}
+	}
+
+	@Test
+	public void bindWhenUsingNoUnboundElementsHandlerIgnoreNestedAndUnboundGrandchildShouldBind()
+			throws Exception {
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("example.foo", "bar");
+		source.put("example.foo.baz", "bar");
+		this.sources.add(source);
+		this.binder = new Binder(this.sources);
+		this.binder.bind("example", Bindable.of(Example.class),
+				new NoUnboundElementsBindHandler(true));
+	}
+
 	public static class Example {
 
 		private String foo;