Added support for default getters and default setters

extra/interface/ap/src/main/java/org/spongepowered/configurate/interfaces/processor/AnnotationDefaults.java

@@ -4,6 +4,7 @@
 
 import com.google.auto.common.MoreTypes;
 import com.squareup.javapoet.AnnotationSpec;
+import javax.lang.model.AnnotatedConstruct;
 import javax.lang.model.element.ExecutableElement;
 import javax.lang.model.type.TypeMirror;
 import org.checkerframework.checker.nullness.qual.Nullable;
@@ -34,6 +35,15 @@ public void process(
             final TypeMirror nodeType,
             final FieldSpecBuilderTracker fieldSpec
     ) throws IllegalStateException {
+        // there are two types of default values, one using annotations and one using the default value of a default method
+
+        // first, handle default value of a default method getter
+        if (element.isDefault() && element.getParameters().isEmpty() && hasNoAnnotationDefaults(element)) {
+            fieldSpec.initializer("$T.super.$L()", element.getEnclosingElement(), element.getSimpleName());
+            return;
+        }
+
+        // if it's not using the default value of a default method, use the annotations
         final @Nullable DefaultBoolean defaultBoolean = annotation(element, DefaultBoolean.class);
         final @Nullable DefaultDecimal defaultDecimal = annotation(element, DefaultDecimal.class);
         final @Nullable DefaultNumeric defaultNumeric = annotation(element, DefaultNumeric.class);
@@ -94,4 +104,13 @@ public void process(
         fieldSpec.initializer(isString ? "$S" : "$L", value);
     }
 
+    static boolean hasNoAnnotationDefaults(final AnnotatedConstruct construct) {
+        for (Class<? extends Annotation> defaultAnnotation : INSTANCE.processes()) {
+            if (annotation(construct, defaultAnnotation) != null) {
+                return false;
+            }
+        }
+        return true;
+    }
+
 }

extra/interface/ap/src/main/java/org/spongepowered/configurate/interfaces/processor/ConfigImplementationGenerator.java

@@ -110,38 +110,13 @@ private void gatherElementSpec(
             if (parameters.size() == 1) {
                 // setter
                 final VariableElement parameter = parameters.get(0);
-
-                final MethodSpec.Builder method = MethodSpec.overriding(element)
-                    .addStatement(
-                        "this.$N = $N",
-                        element.getSimpleName(),
-                        parameter.getSimpleName()
-                    );
-
-                // if it's not void
-                if (!MoreTypes.isTypeOf(Void.TYPE, nodeType)) {
-                    // the return type can be a parent type of parameter, but it has to be assignable
-                    if (!this.processor.typeUtils.isAssignable(parameter.asType(), nodeType)) {
-                        this.processor.error(
-                            "Cannot create a setter with return type %s for argument type %s. Method: %s",
-                            nodeType,
-                            parameter.asType(),
-                            element
-                        );
-                        continue;
-                    }
-                    method.addStatement("return this.$N", element.getSimpleName());
+                final boolean success = handleSetter(element, simpleName, parameter, nodeType, spec);
+                if (!success) {
+                    continue;
                 }
-
-                spec.add(simpleName + "#" + parameter.getSimpleName().toString(), method);
                 nodeType = parameter.asType();
             } else {
-                // getter
-                spec.add(
-                    simpleName,
-                    MethodSpec.overriding(element)
-                        .addStatement("return $N", element.getSimpleName())
-                );
+                handleGetter(element, simpleName, nodeType, spec);
             }
 
             final FieldSpec.Builder fieldSpec = FieldSpec.builder(TypeName.get(nodeType), simpleName, Modifier.PRIVATE);
@@ -158,4 +133,71 @@ private void gatherElementSpec(
         }
     }
 
+    private boolean handleSetter(
+            final ExecutableElement element,
+            final String simpleName,
+            final VariableElement parameter,
+            final TypeMirror returnType,
+            final TypeSpecBuilderTracker spec
+    ) {
+        final MethodSpec.Builder method = MethodSpec.overriding(element);
+
+        // we have two main branches of setters, default non-void setters and non-default any setters
+        if (element.isDefault()) {
+            if (MoreTypes.isTypeOf(Void.TYPE, returnType)) {
+                this.processor.error("A default setter cannot have void as return type. Method: " + element);
+                return false;
+            }
+
+            method.addStatement(
+                    "this.$N = $T.super.$L($N)",
+                    simpleName,
+                    element.getEnclosingElement(),
+                    simpleName,
+                    parameter.getSimpleName()
+            );
+        } else {
+            method.addStatement("this.$N = $N", simpleName, parameter.getSimpleName());
+        }
+
+        // if it's not void
+        if (!MoreTypes.isTypeOf(Void.TYPE, returnType)) {
+            // the return type can be a parent type of parameter, but it has to be assignable
+            if (!this.processor.typeUtils.isAssignable(parameter.asType(), returnType)) {
+                this.processor.error(
+                        "Cannot create a setter with return type %s for argument type %s. Method: %s",
+                        returnType,
+                        parameter.asType(),
+                        element
+                );
+                return false;
+            }
+            method.addStatement("return this.$N", simpleName);
+        }
+
+        spec.add(simpleName + "#" + parameter.getSimpleName(), method);
+        return true;
+    }
+
+    private void handleGetter(
+            final ExecutableElement element,
+            final String simpleName,
+            final TypeMirror nodeType,
+            final TypeSpecBuilderTracker spec
+    ) {
+        // voids aren't valid
+        if (MoreTypes.isTypeOf(Void.TYPE, nodeType)) {
+            this.processor.error(
+                    "Cannot create a getter with return type void for method %s, did you forget to @Exclude this method?",
+                    element
+            );
+        }
+
+        spec.add(
+                simpleName,
+                MethodSpec.overriding(element)
+                        .addStatement("return $N", element.getSimpleName())
+        );
+    }
+
 }

extra/interface/ap/src/test/resources/defaults/CorrectDefaults.java

@@ -64,4 +64,15 @@ public interface CorrectDefaults {
 
     @DefaultString("Hello world!")
     String strawberry();
+
+    @DefaultString("Hi")
+    void tamarillo(String value);
+
+    default String ugli() {
+        return "A fruit";
+    }
+
+    default int velvetApple() {
+        return 500;
+    }
 }

extra/interface/ap/src/test/resources/defaults/CorrectDefaultsImpl.java

@@ -12,7 +12,6 @@
  * Automatically generated implementation of the config */
 @ConfigSerializable
 final class CorrectDefaultsImpl implements CorrectDefaults {
-
     @DefaultBoolean(false)
     private boolean apple = false;
 
@@ -70,6 +69,13 @@ final class CorrectDefaultsImpl implements CorrectDefaults {
     @DefaultString("Hello world!")
     private String strawberry = "Hello world!";
 
+    @DefaultString("Hi")
+    private String tamarillo = "Hi";
+
+    private String ugli = CorrectDefaults.super.ugli();
+
+    private int velvetApple = CorrectDefaults.super.velvetApple();
+
     @Override
     public boolean apple() {
         return apple;
@@ -164,4 +170,19 @@ public String raspberry() {
     public String strawberry() {
         return strawberry;
     }
+
+    @Override
+    public void tamarillo(String value) {
+        this.tamarillo = value;
+    }
+
+    @Override
+    public String ugli() {
+        return ugli;
+    }
+
+    @Override
+    public int velvetApple() {
+        return velvetApple;
+    }
 }

extra/interface/ap/src/test/resources/structure/BasicConfig.java

@@ -9,4 +9,8 @@ public interface BasicConfig {
     void hi(String value);
 
     String hello(String value);
+
+    default String hey(String value) {
+        return "Hello";
+    }
 }

extra/interface/ap/src/test/resources/structure/BasicConfigImpl.java

@@ -12,6 +12,8 @@ final class BasicConfigImpl implements BasicConfig {
 
     private String hi;
 
+    private String hey;
+
     @Override
     public String hello() {
         return hello;
@@ -27,4 +29,10 @@ public String hello(String value) {
         this.hello = value;
         return this.hello;
     }
+
+    @Override
+    public String hey(String value) {
+        this.hey = BasicConfig.super.hey(value);
+        return this.hey;
+    }
 }