Fix binding detection of ConfigurationProperties contributed by @Bean

This commit makes sure that a ConfigurationProperties type contributed
by a `@Bean` factory method uses properties binding regardless of the
presence of a matching constructor.

`@Bean` method makes sure the user is in control and will be responsible
of creating the instance. As a result, binding of properties will not
happen there and therefore can only happen with regular JavaBean
accessors.

Closes gh-18184

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/PropertyDescriptorResolver.java

@@ -51,6 +51,9 @@ class PropertyDescriptorResolver {
 	 */
 	Stream<PropertyDescriptor<?>> resolve(TypeElement type, ExecutableElement factoryMethod) {
 		TypeElementMembers members = new TypeElementMembers(this.environment, type);
+		if (factoryMethod != null) {
+			return resolveJavaBeanProperties(type, factoryMethod, members);
+		}
 		ExecutableElement constructor = resolveConstructor(type);
 		if (constructor != null) {
 			return resolveConstructorProperties(type, factoryMethod, members, constructor);

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationprocessor/MethodBasedMetadataGenerationTests.java

@@ -28,6 +28,7 @@ import org.springframework.boot.configurationsample.method.PackagePrivateMethodC
 import org.springframework.boot.configurationsample.method.PrivateMethodConfig;
 import org.springframework.boot.configurationsample.method.ProtectedMethodConfig;
 import org.springframework.boot.configurationsample.method.PublicMethodConfig;
+import org.springframework.boot.configurationsample.method.SingleConstructorMethodConfig;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -86,6 +87,17 @@ class MethodBasedMetadataGenerationTests extends AbstractMetadataGenerationTests
 				.has(Metadata.withProperty("conflict.value", String.class).fromSource(MethodAndClassConfig.class));
 	}
 
+	@Test
+	void singleConstructorMethodConfig() {
+		ConfigurationMetadata metadata = compile(SingleConstructorMethodConfig.class);
+		assertThat(metadata).doesNotHave(Metadata.withProperty("foo.my-service", Object.class)
+				.fromSource(SingleConstructorMethodConfig.Foo.class));
+		assertThat(metadata).has(
+				Metadata.withProperty("foo.name", String.class).fromSource(SingleConstructorMethodConfig.Foo.class));
+		assertThat(metadata).has(Metadata.withProperty("foo.flag", Boolean.class).withDefaultValue(false)
+				.fromSource(SingleConstructorMethodConfig.Foo.class));
+	}
+
 	@Test
 	void emptyTypeMethodConfig() {
 		ConfigurationMetadata metadata = compile(EmptyTypeMethodConfig.class);

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationsample/method/SingleConstructorMethodConfig.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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.springframework.boot.configurationsample.method;
+
+import org.springframework.boot.configurationsample.ConfigurationProperties;
+
+/**
+ * Sample for testing method configuration that uses a constructor that should not be
+ * associated to constructor binding.
+ *
+ * @author Stephane Nicoll
+ */
+public class SingleConstructorMethodConfig {
+
+	@ConfigurationProperties(prefix = "foo")
+	public Foo foo() {
+		return new Foo(new Object());
+	}
+
+	public static class Foo {
+
+		private String name;
+
+		private boolean flag;
+
+		private final Object myService;
+
+		public Foo(Object myService) {
+			this.myService = myService;
+		}
+
+		public String getName() {
+			return this.name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+
+		public boolean isFlag() {
+			return this.flag;
+		}
+
+		public void setFlag(boolean flag) {
+			this.flag = flag;
+		}
+
+	}
+
+}