Merge pull request #19099 from ChunMengLu

* pr/19099:
  Polish "Detect config props using builder pattern and generics"
  Detect config props using builder pattern and generics

Closes gh-19099

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

@@ -44,15 +44,18 @@ class TypeElementMembers {
 
 	private final MetadataGenerationEnvironment env;
 
+	private final TypeElement targetType;
+
 	private final Map<String, VariableElement> fields = new LinkedHashMap<>();
 
 	private final Map<String, ExecutableElement> publicGetters = new LinkedHashMap<>();
 
 	private final Map<String, List<ExecutableElement>> publicSetters = new LinkedHashMap<>();
 
-	TypeElementMembers(MetadataGenerationEnvironment env, TypeElement element) {
+	TypeElementMembers(MetadataGenerationEnvironment env, TypeElement targetType) {
 		this.env = env;
-		process(element);
+		this.targetType = targetType;
+		process(targetType);
 	}
 
 	private void process(TypeElement element) {
@@ -116,8 +119,19 @@ class TypeElementMembers {
 
 	private boolean isSetterReturnType(ExecutableElement method) {
 		TypeMirror returnType = method.getReturnType();
-		return (TypeKind.VOID == returnType.getKind()
+		if (TypeKind.VOID == returnType.getKind()) {
-				|| this.env.getTypeUtils().isSameType(method.getEnclosingElement().asType(), returnType));
+			return true;
+		}
+		if (TypeKind.DECLARED == returnType.getKind()
+				&& this.env.getTypeUtils().isSameType(method.getEnclosingElement().asType(), returnType)) {
+			return true;
+		}
+		if (TypeKind.TYPEVAR == returnType.getKind()) {
+			String resolvedType = this.env.getTypeUtils().getType(this.targetType, returnType);
+			return (resolvedType != null
+					&& resolvedType.equals(this.env.getTypeUtils().getQualifiedName(this.targetType)));
+		}
+		return false;
 	}
 
 	private String getAccessorName(String methodName) {

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

@@ -22,6 +22,7 @@ import org.springframework.boot.configurationprocessor.metadata.ConfigurationMet
 import org.springframework.boot.configurationprocessor.metadata.Metadata;
 import org.springframework.boot.configurationsample.generic.AbstractGenericProperties;
 import org.springframework.boot.configurationsample.generic.ComplexGenericProperties;
+import org.springframework.boot.configurationsample.generic.ConcreteBuilderProperties;
 import org.springframework.boot.configurationsample.generic.GenericConfig;
 import org.springframework.boot.configurationsample.generic.SimpleGenericProperties;
 import org.springframework.boot.configurationsample.generic.UnresolvedGenericProperties;
@@ -110,4 +111,15 @@ class GenericsMetadataGenerationTests extends AbstractMetadataGenerationTests {
 		assertThat(metadata.getItems()).hasSize(3);
 	}
 
+	@Test
+	void builderPatternWithGenericReturnType() {
+		ConfigurationMetadata metadata = compile(ConcreteBuilderProperties.class);
+		assertThat(metadata).has(Metadata.withGroup("builder").fromSource(ConcreteBuilderProperties.class));
+		assertThat(metadata).has(
+				Metadata.withProperty("builder.number", Integer.class).fromSource(ConcreteBuilderProperties.class));
+		assertThat(metadata).has(
+				Metadata.withProperty("builder.description", String.class).fromSource(ConcreteBuilderProperties.class));
+		assertThat(metadata.getItems()).hasSize(3);
+	}
+
 }

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationsample/generic/ConcreteBuilderProperties.java

@@ -0,0 +1,40 @@
+/*
+ * 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.generic;
+
+import org.springframework.boot.configurationsample.ConfigurationProperties;
+
+/**
+ * Builder pattern with a resolved generic
+ *
+ * @author Stephane Nicoll
+ */
+@ConfigurationProperties("builder")
+public class ConcreteBuilderProperties extends GenericBuilderProperties<ConcreteBuilderProperties> {
+
+	private String description;
+
+	public String getDescription() {
+		return this.description;
+	}
+
+	public ConcreteBuilderProperties setDescription(String description) {
+		this.description = description;
+		return this;
+	}
+
+}

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationsample/generic/GenericBuilderProperties.java

@@ -0,0 +1,38 @@
+/*
+ * 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.generic;
+
+/**
+ * A configuration properties that uses the builder pattern with a generic.
+ *
+ * @param <T> the type of the return type
+ * @author Stephane Nicoll
+ */
+public class GenericBuilderProperties<T extends GenericBuilderProperties<T>> {
+
+	private int number;
+
+	public int getNumber() {
+		return this.number;
+	}
+
+	public T setNumber(int number) {
+		this.number = number;
+		return (T) this;
+	}
+
+}