introduction of @SuperBuilder and a testcase.

src/core/lombok/Builder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2013-2017 The Project Lombok Authors.
+ * Copyright (C) 2013-2018 The Project Lombok Authors.
  * 
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -55,8 +55,8 @@ import java.lang.annotation.Target;
  * 
  * <pre>
  * &#064;Builder
- * class Example {
- * 	private int foo;
+ * class Example&lt;T&gt; {
+ * 	private T foo;
  * 	private final String bar;
  * }
  * </pre>
@@ -103,6 +103,8 @@ import java.lang.annotation.Target;
  * 	}
  * }
  * </pre>
+ * 
+ * @see Singular
  */
 @Target({TYPE, METHOD, CONSTRUCTOR})
 @Retention(SOURCE)
@@ -131,48 +133,6 @@ public @interface Builder {
 	 */
 	String builderClassName() default "";
 	
-	/**
-	 * Should the generated builder extend the parent class's builder?
-	 * 
-	 * If {@code true}, the generated builder class will extend the builder of the
-	 * superclass. This means the builder also contains the methods for fields from
-	 * the superclass.
-	 * <p>
-	 * Note that both this builder and the superclass' builder must be a builder
-	 * for a type (so, not for a static method or a constructor). You must mark
-	 * the parent extendable: {@code @Builder(extensible = true)}.
-	 * <p>
-	 * This builder will also be {@code extensible = true} if you set {@code inherit = true}.
-	 * 
-	 * @see #extensible()
-	 */
-	boolean inherit() default false;
-	
-	/**
-	 * Should the generated builder be extensible by subclasses?
-	 * 
-	 * If {@code true} the generated builder class will be extensible by
-	 * {@code @Builder} classes of this class's subclasses, by marking them
-	 * with {@code @Builder(inherit = true)}.
-	 * <p>
-	 * The {@code @Builder} extensible system only works for {@code @Builder}
-	 * annotations on types (so, not on a static method or a constructor).
-	 * 
-	 * @see #inherit()
-	 */
-	boolean extensible() default false;
-	
-	/**
-	 * Name of the builder class in the superclass.
-	 * 
-	 * Only relevant if {@code inherit = true}
-	 * 
-	 * Default: {@code (SuperclassTypeName)Builder}.
-	 * 
-	 * @see #inherit()
-	 */
-	String superclassBuilderClassName() default "";
-	
 	/**
 	 * If true, generate an instance method to obtain a builder that is initialized with the values of this instance.
 	 * Legal only if {@code @Builder} is used on a constructor, on the type itself, or on a static method that returns

src/core/lombok/experimental/SuperBuilder.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2018 The Project Lombok Authors.
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package lombok.experimental;
+
+import static java.lang.annotation.ElementType.*;
+import static java.lang.annotation.RetentionPolicy.*;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+import lombok.Singular;
+
+/**
+ * The SuperBuilder annotation creates a so-called 'builder' aspect to the class that is annotated with {@code @SuperBuilder}, but which works well when extending.
+ * It is similar to {@code @Builder}, except it is only legal on types, is less configurable, but allows you to {@code extends} other builder-able classes.
+ * <p>
+ * All classes in the hierarchy must be annotated with {@code @SuperBuilder}.
+ * <p>
+ * Lombok generates 2 inner 'builder' classes, which extend the parent class' builder class (unless your class doesn't have an extends clause).
+ * Lombok also generates a static method named {@code builder()}, and a protected constructor that takes 1 argument of the builderclass type.
+ * <p>
+ * The <code><strong>T</strong>Builder</code> class contains 1 method for each parameter of the annotated
+ * constructor / method (each field, when annotating a class), which returns the builder itself.
+ * The builder also has a <code>build()</code> method which returns a completed instance of the original type.
+ * <p>
+ * Complete documentation is found at <a href="https://projectlombok.org/features/experimental/SuperBuilder">the project lombok features page for &#64;SuperBuilder</a>.
+ * 
+ * @see Singular
+ */
+@Target(TYPE)
+@Retention(SOURCE)
+public @interface SuperBuilder {
+	/** @return Name of the method that creates a new builder instance. Default: {@code builder}. */
+	String builderMethodName() default "builder";
+	
+	/** @return Name of the method in the builder class that creates an instance of your {@code @Builder}-annotated class. */
+	String buildMethodName() default "build";
+	
+	// toBuilder also requires a two-stage system where each class gets its own toBuilder but calls on a second method (and also calls parentclass's method)
+	// to fill the builder, as this class does not know what fields to pass on to the builder. Let's consider this, but only for milestone 2.
+	/*
+	 * If true, generate an instance method to obtain a builder that is initialized with the values of this instance.
+	 * 
+	 * @return Whether to generate a {@code toBuilder()} method.
+	 */
+//	boolean toBuilder() default false;
+}

test/transform/resource/after-delombok/SuperBuilderBasic.java

@@ -0,0 +1,112 @@
+import java.util.List;
+
+public class SuperBuilderBasic {
+	public static class Parent {
+		int field1;
+		List<String> items;
+		protected Parent(final ParentBuilder<?, ?> b) {
+			this.field1 = b.field1;
+			java.util.List<String> items;
+			switch (b.items == null ? 0 : b.items.size()) {
+			case 0: 
+				items = java.util.Collections.emptyList();
+				break;
+			case 1: 
+				items = java.util.Collections.singletonList(b.items.get(0));
+				break;
+			default: 
+				items = java.util.Collections.unmodifiableList(new java.util.ArrayList<String>(b.items));
+			}
+			this.items = items;
+		}
+		private static class ParentBuilderImpl extends ParentBuilder<Parent, ParentBuilderImpl> {
+			@Override
+			public Parent build() {
+				return new Parent(this);
+			}
+			
+			@Override
+			public ParentBuilderImpl self() {
+				return this;
+			}
+		}
+		public abstract static class ParentBuilder<C extends Parent, B extends ParentBuilder<C, B>> {
+			@java.lang.SuppressWarnings("all")
+			private int field1;
+			@java.lang.SuppressWarnings("all")
+			private java.util.ArrayList<String> items;
+			@java.lang.SuppressWarnings("all")
+			ParentBuilder() {
+			}
+			@java.lang.SuppressWarnings("all")
+			public B field1(final int field1) {
+				this.field1 = field1;
+				return self();
+			}
+			@java.lang.SuppressWarnings("all")
+			public B item(final String item) {
+				if (this.items == null) this.items = new java.util.ArrayList<String>();
+				this.items.add(item);
+				return self();
+			}
+			@java.lang.SuppressWarnings("all")
+			public B items(final java.util.Collection<? extends String> items) {
+				if (this.items == null) this.items = new java.util.ArrayList<String>();
+				this.items.addAll(items);
+				return self();
+			}
+			@java.lang.SuppressWarnings("all")
+			public B clearItems() {
+				if (this.items != null) this.items.clear();
+				return self();
+			}
+			@java.lang.SuppressWarnings("all")
+			protected abstract B self();
+			@java.lang.SuppressWarnings("all")
+			public abstract C build();
+		}
+		public static ParentBuilder<?, ?> builder() {
+			return new ParentBuilderImpl();
+		}
+	}
+	public static class Child extends Parent {
+		double field3;
+		protected Child(ChildBuilder<?, ?> b) {
+			super(b);
+			this.field3 = b.field3;
+		}
+		private static class ChildBuilderImpl extends ChildBuilder<Child, ChildBuilderImpl> {
+			@Override
+			public Child build() {
+				return new Child(this);
+			}
+			
+			@Override
+			public ChildBuilderImpl self() {
+				return this;
+			}
+		}
+		public abstract static class ChildBuilder<C extends Child, B extends ChildBuilder<C, B>> extends Parent.ParentBuilder<Child, B> {
+			@java.lang.SuppressWarnings("all")
+			private double field3;
+			@java.lang.SuppressWarnings("all")
+			ChildBuilder() {
+			}
+			@java.lang.SuppressWarnings("all")
+			public B field3(final double field3) {
+				this.field3 = field3;
+				return self();
+			}
+			@java.lang.SuppressWarnings("all")
+			protected abstract B self();
+			@java.lang.SuppressWarnings("all")
+			public abstract C build();
+		}
+		public static ChildBuilder<?, ?> builder() {
+			return new ChildBuilderImpl();
+		}
+	}
+	public static void test() {
+		Child x = Child.builder().field3(0.0).field1(5).item("").build();
+	}
+}

test/transform/resource/before/SuperBuilderBasic.java

@@ -1,15 +1,15 @@
-import lombok.Builder;
+import lombok.experimental.SuperBuilder;
 import lombok.Singular;
 import java.util.List;
 
-public class BuilderWithInherit {
-	@Builder(extensible = true)
+public class SuperBuilderBasic {
+	@SuperBuilder
 	public static class Parent {
 		int field1;
 		@Singular List<String> items;
 	}
 	
-	@Builder(inherit = true)
+	@SuperBuilder
 	public static class Child extends Parent {
 		double field3;
 	}