[issue #2368] [withBy] support for javac

src/core/lombok/ConfigurationKeys.java

@@ -643,6 +643,15 @@ public class ConfigurationKeys {
 	 */
 	public static final ConfigurationKey<FlagUsageType> SUPERBUILDER_FLAG_USAGE = new ConfigurationKey<FlagUsageType>("lombok.superBuilder.flagUsage", "Emit a warning or error if @SuperBuilder is used.") {};
 
+	// ----- WithBy -----
+	
+	/**
+	 * lombok configuration: {@code lombok.withBy.flagUsage} = {@code WARNING} | {@code ERROR}.
+	 * 
+	 * If set, <em>any</em> usage of {@code @WithBy} results in a warning / error.
+	 */
+	public static final ConfigurationKey<FlagUsageType> WITHBY_FLAG_USAGE = new ConfigurationKey<FlagUsageType>("lombok.withBy.flagUsage", "Emit a warning or error if @WithBy is used.") {};
+	
 	// ----- Configuration System -----
 	
 	/**

src/core/lombok/core/handlers/HandlerUtil.java

@@ -530,6 +530,20 @@ public class HandlerUtil {
 		return toAccessorName(ast, accessors, fieldName, isBoolean, "with", "with", false);
 	}
 	
+	/**
+	 * Generates a withBy name from a given field name.
+	 * 
+	 * Strategy: The same as the {@code toWithName} strategy, but then append {@code "By"} at the end.
+	 * 
+	 * @param accessors Accessors configuration.
+	 * @param fieldName the name of the field.
+	 * @param isBoolean if the field is of type 'boolean'. For fields of type {@code java.lang.Boolean}, you should provide {@code false}.
+	 * @return The with name for this field, or {@code null} if this field does not fit expected patterns and therefore cannot be turned into a getter name.
+	 */
+	public static String toWithByName(AST<?, ?, ?> ast, AnnotationValues<Accessors> accessors, CharSequence fieldName, boolean isBoolean) {
+		return toAccessorName(ast, accessors, fieldName, isBoolean, "with", "with", false) + "By";
+	}
+	
 	private static String toAccessorName(AST<?, ?, ?> ast, AnnotationValues<Accessors> accessors, CharSequence fieldName, boolean isBoolean,
 			String booleanPrefix, String normalPrefix, boolean adhereToFluent) {
 		
@@ -601,6 +615,23 @@ public class HandlerUtil {
 		return toAllAccessorNames(ast, accessors, fieldName, isBoolean, "with", "with", false);
 	}
 	
+	/**
+	 * Returns all names of methods that would represent the withBy for a field with the provided name.
+	 * 
+	 * For example if {@code isBoolean} is true, then a field named {@code isRunning} would produce:<br />
+	 * {@code [withRunningBy, withIsRunningBy]}
+	 * 
+	 * @param accessors Accessors configuration.
+	 * @param fieldName the name of the field.
+	 * @param isBoolean if the field is of type 'boolean'. For fields of type 'java.lang.Boolean', you should provide {@code false}.
+	 */
+	public static List<String> toAllWithByNames(AST<?, ?, ?> ast, AnnotationValues<Accessors> accessors, CharSequence fieldName, boolean isBoolean) {
+		List<String> in = toAllAccessorNames(ast, accessors, fieldName, isBoolean, "with", "with", false);
+		if (!(in instanceof ArrayList)) in = new ArrayList<String>(in);
+		for (int i = 0; i < in.size(); i++) in.set(i, in.get(i) + "By");
+		return in;
+	}
+	
 	private static List<String> toAllAccessorNames(AST<?, ?, ?> ast, AnnotationValues<Accessors> accessors, CharSequence fieldName, boolean isBoolean,
 			String booleanPrefix, String normalPrefix, boolean adhereToFluent) {
 		
@@ -634,7 +665,6 @@ public class HandlerUtil {
 		}
 		
 		return new ArrayList<String>(names);
-		
 	}
 	
 	private static List<String> toBaseNames(CharSequence fieldName, boolean isBoolean, boolean fluent) {

src/core/lombok/eclipse/handlers/EclipseHandlerUtil.java

@@ -1549,7 +1549,7 @@ public class EclipseHandlerUtil {
 	
 	/**
 	 * Translates the given field into all possible getter names.
-	 * Convenient wrapper around {@link TransformationsUtil#toAllGetterNames(lombok.core.AnnotationValues, CharSequence, boolean)}.
+	 * Convenient wrapper around {@link HandlerUtil#toAllGetterNames(lombok.core.AnnotationValues, CharSequence, boolean)}.
 	 */
 	public static List<String> toAllGetterNames(EclipseNode field, boolean isBoolean) {
 		return HandlerUtil.toAllGetterNames(field.getAst(), getAccessorsForField(field), field.getName(), isBoolean);
@@ -1558,7 +1558,7 @@ public class EclipseHandlerUtil {
 	/**
 	 * @return the likely getter name for the stated field. (e.g. private boolean foo; to isFoo).
 	 * 
-	 * Convenient wrapper around {@link TransformationsUtil#toGetterName(lombok.core.AnnotationValues, CharSequence, boolean)}.
+	 * Convenient wrapper around {@link HandlerUtil#toGetterName(lombok.core.AnnotationValues, CharSequence, boolean)}.
 	 */
 	public static String toGetterName(EclipseNode field, boolean isBoolean) {
 		return HandlerUtil.toGetterName(field.getAst(), getAccessorsForField(field), field.getName(), isBoolean);
@@ -1566,7 +1566,7 @@ public class EclipseHandlerUtil {
 	
 	/**
 	 * Translates the given field into all possible setter names.
-	 * Convenient wrapper around {@link TransformationsUtil#toAllSetterNames(lombok.core.AnnotationValues, CharSequence, boolean)}.
+	 * Convenient wrapper around {@link HandlerUtil#toAllSetterNames(lombok.core.AnnotationValues, CharSequence, boolean)}.
 	 */
 	public static java.util.List<String> toAllSetterNames(EclipseNode field, boolean isBoolean) {
 		return HandlerUtil.toAllSetterNames(field.getAst(), getAccessorsForField(field), field.getName(), isBoolean);
@@ -1575,7 +1575,7 @@ public class EclipseHandlerUtil {
 	/**
 	 * @return the likely setter name for the stated field. (e.g. private boolean foo; to setFoo).
 	 * 
-	 * Convenient wrapper around {@link TransformationsUtil#toSetterName(lombok.core.AnnotationValues, CharSequence, boolean)}.
+	 * Convenient wrapper around {@link HandlerUtil#toSetterName(lombok.core.AnnotationValues, CharSequence, boolean)}.
 	 */
 	public static String toSetterName(EclipseNode field, boolean isBoolean) {
 		return HandlerUtil.toSetterName(field.getAst(), getAccessorsForField(field), field.getName(), isBoolean);
@@ -1583,7 +1583,7 @@ public class EclipseHandlerUtil {
 	
 	/**
 	 * Translates the given field into all possible with names.
-	 * Convenient wrapper around {@link TransformationsUtil#toAllWithNames(lombok.core.AnnotationValues, CharSequence, boolean)}.
+	 * Convenient wrapper around {@link HandlerUtil#toAllWithNames(lombok.core.AnnotationValues, CharSequence, boolean)}.
 	 */
 	public static java.util.List<String> toAllWithNames(EclipseNode field, boolean isBoolean) {
 		return HandlerUtil.toAllWithNames(field.getAst(), getAccessorsForField(field), field.getName(), isBoolean);
@@ -1592,7 +1592,7 @@ public class EclipseHandlerUtil {
 	/**
 	 * @return the likely with name for the stated field. (e.g. private boolean foo; to withFoo).
 	 * 
-	 * Convenient wrapper around {@link TransformationsUtil#toWithName(lombok.core.AnnotationValues, CharSequence, boolean)}.
+	 * Convenient wrapper around {@link HandlerUtil#toWithName(lombok.core.AnnotationValues, CharSequence, boolean)}.
 	 */
 	public static String toWithName(EclipseNode field, boolean isBoolean) {
 		return HandlerUtil.toWithName(field.getAst(), getAccessorsForField(field), field.getName(), isBoolean);

src/core/lombok/experimental/WithBy.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2020 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 java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import lombok.AccessLevel;
+
+/**
+ * Put on any field to make lombok build a 'withBy' - a withFieldNameBy method which produces a clone of this object (except for 1 field which gets a new value).
+ * <p>
+ * Complete documentation is found at <a href="https://projectlombok.org/features/experimental/WithBy">the project lombok features page for &#64;WithBy</a>.
+ * <p>
+ * Example:
+ * <pre>
+ *     private &#64;WithBy final int foo;
+ *     private &#64;WithBy final String bar;
+ * </pre>
+ * 
+ * will generate:
+ * 
+ * <pre>
+ *     public SELF_TYPE withFooBy(@lombok.NonNull IntUnaryOperator operator) {
+ *         int foo = operator.apply(this.foo);
+ *         return this.foo == foo ? this : new SELF_TYPE(foo, bar);
+ *     }
+ *     public SELF_TYPE withBarBy(@lombok.NonNull Function&lt;? super String, ? extends String&gt; operator) {
+ *         String bar = operator.apply(this.bar);
+ *         return this.bar == bar ? this : new SELF_TYPE(foo, bar);
+ *     }
+ * </pre>
+ * <p>
+ * This annotation can also be applied to a class, in which case it'll be as if all non-static fields that don't already have
+ * a {@code WithBy} annotation have the annotation.
+ * <p>
+ * This annotation is primarily useful for hierarchical immutable data structures. For example:
+ * 
+ * <pre>
+ *     class Movie {
+ *         &#64;WithBy private final Director director;
+ *     }
+ *     
+ *     class Director {
+ *         &#64;WithBy private final LocalDate birthDate;
+ *     }
+ * </pre>
+ * 
+ * Using plain old {@code @With}, to increment a movie's director's birth date by one, you would write:
+ * 
+ * <pre>
+ *     movie = movie.withDirector(movie.getDirector().withBirthDate(movie.getDirector().getBirthDate().plusDays(1)));
+ * </pre>
+ * 
+ * but with {@code @WithBy}, you'd write:
+ * 
+ * <pre>
+ *     movie = movie.withDirectorBy(d -> d.withBirthDateBy(bd -> bd.plusDays(1)));
+ * </pre>
+ */
+@Target({ElementType.FIELD, ElementType.TYPE})
+@Retention(RetentionPolicy.SOURCE)
+public @interface WithBy {
+	/**
+	 * If you want your with method to be non-public, you can specify an alternate access level here.
+	 * 
+	 * @return The method will be generated with this access modifier.
+	 */
+	AccessLevel value() default AccessLevel.PUBLIC;
+	
+	/**
+	 * Any annotations listed here are put on the generated method.
+	 * The syntax for this feature depends on JDK version (nothing we can do about that; it's to work around javac bugs).<br>
+	 * up to JDK7:<br>
+	 *  {@code @With(onMethod=@__({@AnnotationsGoHere}))}<br>
+	 * from JDK8:<br>
+	 *  {@code @With(onMethod_={@AnnotationsGohere})} // note the underscore after {@code onMethod}.
+	 * 
+	 * @return List of annotations to apply to the generated method.
+	 */
+	AnyAnnotation[] onMethod() default {};
+	
+	/**
+	  * Placeholder annotation to enable the placement of annotations on the generated code.
+	  * @deprecated Don't use this annotation, ever - Read the documentation.
+	  */
+	@Deprecated
+	@Retention(RetentionPolicy.SOURCE)
+	@Target({})
+	@interface AnyAnnotation {}
+}

src/core/lombok/javac/handlers/HandleWithBy.java

@@ -0,0 +1,342 @@
+/*
+ * Copyright (C) 2020 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.javac.handlers;
+
+import static lombok.core.handlers.HandlerUtil.*;
+import static lombok.javac.handlers.JavacHandlerUtil.*;
+
+import java.util.Collection;
+
+import javax.lang.model.type.TypeKind;
+
+import lombok.AccessLevel;
+import lombok.ConfigurationKeys;
+import lombok.core.AST.Kind;
+import lombok.core.AnnotationValues;
+import lombok.core.LombokImmutableList;
+import lombok.core.configuration.CheckerFrameworkVersion;
+import lombok.experimental.WithBy;
+import lombok.javac.Javac;
+import lombok.javac.JavacAnnotationHandler;
+import lombok.javac.JavacNode;
+import lombok.javac.JavacTreeMaker;
+import lombok.javac.JavacTreeMaker.TypeTag;
+import lombok.javac.handlers.JavacHandlerUtil.CopyJavadoc;
+
+import org.mangosdk.spi.ProviderFor;
+
+import com.sun.tools.javac.code.BoundKind;
+import com.sun.tools.javac.code.Flags;
+import com.sun.tools.javac.code.Type;
+import com.sun.tools.javac.code.Symbol.ClassSymbol;
+import com.sun.tools.javac.tree.JCTree.JCAnnotation;
+import com.sun.tools.javac.tree.JCTree.JCBlock;
+import com.sun.tools.javac.tree.JCTree.JCClassDecl;
+import com.sun.tools.javac.tree.JCTree.JCExpression;
+import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
+import com.sun.tools.javac.tree.JCTree.JCNewClass;
+import com.sun.tools.javac.tree.JCTree.JCPrimitiveTypeTree;
+import com.sun.tools.javac.tree.JCTree.JCReturn;
+import com.sun.tools.javac.tree.JCTree.JCStatement;
+import com.sun.tools.javac.tree.JCTree.JCTypeParameter;
+import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
+import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
+import com.sun.tools.javac.util.List;
+import com.sun.tools.javac.util.ListBuffer;
+import com.sun.tools.javac.util.Name;
+
+/**
+ * Handles the {@code lombok.With} annotation for javac.
+ */
+@ProviderFor(JavacAnnotationHandler.class)
+public class HandleWithBy extends JavacAnnotationHandler<WithBy> {
+	public void generateWithByForType(JavacNode typeNode, JavacNode errorNode, AccessLevel level, boolean checkForTypeLevelWithBy) {
+		if (checkForTypeLevelWithBy) {
+			if (hasAnnotation(WithBy.class, typeNode)) {
+				//The annotation will make it happen, so we can skip it.
+				return;
+			}
+		}
+		
+		JCClassDecl typeDecl = null;
+		if (typeNode.get() instanceof JCClassDecl) typeDecl = (JCClassDecl) typeNode.get();
+		long modifiers = typeDecl == null ? 0 : typeDecl.mods.flags;
+		boolean notAClass = (modifiers & (Flags.INTERFACE | Flags.ANNOTATION | Flags.ENUM)) != 0;
+		
+		if (typeDecl == null || notAClass) {
+			errorNode.addError("@WithBy is only supported on a class or a field.");
+			return;
+		}
+		
+		for (JavacNode field : typeNode.down()) {
+			if (field.getKind() != Kind.FIELD) continue;
+			JCVariableDecl fieldDecl = (JCVariableDecl) field.get();
+			//Skip fields that start with $
+			if (fieldDecl.name.toString().startsWith("$")) continue;
+			//Skip static fields.
+			if ((fieldDecl.mods.flags & Flags.STATIC) != 0) continue;
+			//Skip final initialized fields.
+			if ((fieldDecl.mods.flags & Flags.FINAL) != 0 && fieldDecl.init != null) continue;
+			
+			generateWithByForField(field, errorNode.get(), level);
+		}
+	}
+	
+	/**
+	 * Generates a withBy on the stated field.
+	 * 
+	 * The difference between this call and the handle method is as follows:
+	 * 
+	 * If there is a {@code lombok.experimental.WithBy} annotation on the field, it is used and the
+	 * same rules apply (e.g. warning if the method already exists, stated access level applies).
+	 * If not, the with is still generated if it isn't already there, though there will not
+	 * be a warning if its already there. The default access level is used.
+	 * 
+	 * @param fieldNode The node representing the field you want a with for.
+	 * @param pos The node responsible for generating the {@code @WithBy} annotation.
+	 */
+	public void generateWithByForField(JavacNode fieldNode, DiagnosticPosition pos, AccessLevel level) {
+		if (hasAnnotation(WithBy.class, fieldNode)) {
+			//The annotation will make it happen, so we can skip it.
+			return;
+		}
+		
+		createWithByForField(level, fieldNode, fieldNode, false, List.<JCAnnotation>nil());
+	}
+	
+	@Override public void handle(AnnotationValues<WithBy> annotation, JCAnnotation ast, JavacNode annotationNode) {
+		handleExperimentalFlagUsage(annotationNode, ConfigurationKeys.WITHBY_FLAG_USAGE, "@WithBy");
+		
+		Collection<JavacNode> fields = annotationNode.upFromAnnotationToFields();
+		deleteAnnotationIfNeccessary(annotationNode, WithBy.class);
+		deleteImportFromCompilationUnit(annotationNode, "lombok.AccessLevel");
+		JavacNode node = annotationNode.up();
+		AccessLevel level = annotation.getInstance().value();
+		
+		if (level == AccessLevel.NONE || node == null) return;
+		
+		List<JCAnnotation> onMethod = unboxAndRemoveAnnotationParameter(ast, "onMethod", "@WithBy(onMethod", annotationNode);
+		
+		switch (node.getKind()) {
+		case FIELD:
+			createWithByForFields(level, fields, annotationNode, true, onMethod);
+			break;
+		case TYPE:
+			if (!onMethod.isEmpty()) annotationNode.addError("'onMethod' is not supported for @WithBy on a type.");
+			generateWithByForType(node, annotationNode, level, false);
+			break;
+		}
+	}
+	
+	public void createWithByForFields(AccessLevel level, Collection<JavacNode> fieldNodes, JavacNode errorNode, boolean whineIfExists, List<JCAnnotation> onMethod) {
+		for (JavacNode fieldNode : fieldNodes) {
+			createWithByForField(level, fieldNode, errorNode, whineIfExists, onMethod);
+		}
+	}
+	
+	public void createWithByForField(AccessLevel level, JavacNode fieldNode, JavacNode source, boolean strictMode, List<JCAnnotation> onMethod) {
+		JavacNode typeNode = fieldNode.up();
+		boolean makeAbstract = typeNode != null && typeNode.getKind() == Kind.TYPE && (((JCClassDecl) typeNode.get()).mods.flags & Flags.ABSTRACT) != 0;
+		
+		if (fieldNode.getKind() != Kind.FIELD) {
+			fieldNode.addError("@WithBy is only supported on a class or a field.");
+			return;
+		}
+		
+		JCVariableDecl fieldDecl = (JCVariableDecl) fieldNode.get();
+		String methodName = toWithByName(fieldNode);
+		
+		if (methodName == null) {
+			fieldNode.addWarning("Not generating a withXBy method for this field: It does not fit your @Accessors prefix list.");
+			return;
+		}
+		
+		if ((fieldDecl.mods.flags & Flags.STATIC) != 0) {
+			if (strictMode) fieldNode.addWarning("Not generating " + methodName + " for this field: WithBy methods cannot be generated for static fields.");
+			return;
+		}
+		
+		if ((fieldDecl.mods.flags & Flags.FINAL) != 0 && fieldDecl.init != null) {
+			if (strictMode) fieldNode.addWarning("Not generating " + methodName + " for this field: WithBy methods cannot be generated for final, initialized fields.");
+			return;
+		}
+		
+		if (fieldDecl.name.toString().startsWith("$")) {
+			if (strictMode) fieldNode.addWarning("Not generating " + methodName + " for this field: WithBy methods cannot be generated for fields starting with $.");
+			return;
+		}
+		
+		for (String altName : toAllWithByNames(fieldNode)) {
+			switch (methodExists(altName, fieldNode, false, 1)) {
+			case EXISTS_BY_LOMBOK:
+				return;
+			case EXISTS_BY_USER:
+				if (strictMode) {
+					String altNameExpl = "";
+					if (!altName.equals(methodName)) altNameExpl = String.format(" (%s)", altName);
+					fieldNode.addWarning(
+						String.format("Not generating %s(): A method with that name already exists%s", methodName, altNameExpl));
+				}
+				return;
+			default:
+			case NOT_EXISTS:
+				//continue scanning the other alt names.
+			}
+		}
+		
+		long access = toJavacModifier(level);
+		
+		JCMethodDecl createdWithBy = createWithBy(access, fieldNode, fieldNode.getTreeMaker(), source, onMethod, makeAbstract);
+		ClassSymbol sym = ((JCClassDecl) fieldNode.up().get()).sym;
+		Type returnType = sym == null ? null : sym.type;
+		
+		injectMethod(typeNode, createdWithBy, List.<Type>of(getMirrorForFieldType(fieldNode)), returnType);
+	}
+	
+	private static final LombokImmutableList<String> NAME_JUF_FUNCTION = LombokImmutableList.of("java", "util", "function", "Function");
+	private static final LombokImmutableList<String> NAME_JUF_OP = LombokImmutableList.of("java", "util", "function", "UnaryOperator");
+	private static final LombokImmutableList<String> NAME_JUF_DOUBLEOP = LombokImmutableList.of("java", "util", "function", "DoubleUnaryOperator");
+	private static final LombokImmutableList<String> NAME_JUF_INTOP = LombokImmutableList.of("java", "util", "function", "IntUnaryOperator");
+	private static final LombokImmutableList<String> NAME_JUF_LONGOP = LombokImmutableList.of("java", "util", "function", "LongUnaryOperator");
+	
+	public JCMethodDecl createWithBy(long access, JavacNode field, JavacTreeMaker maker, JavacNode source, List<JCAnnotation> onMethod, boolean makeAbstract) {
+		String withByName = toWithByName(field);
+		if (withByName == null) return null;
+		
+		JCVariableDecl fieldDecl = (JCVariableDecl) field.get();
+		
+		Name methodName = field.toName(withByName);
+		
+		JCExpression returnType = cloneSelfType(field);
+		
+		JCBlock methodBody = null;
+		long flags = JavacHandlerUtil.addFinalIfNeeded(Flags.PARAMETER, field.getContext());
+		
+		LombokImmutableList<String> functionalInterfaceName = null;
+		TypeTag requiredCast = null;
+		JCExpression parameterizer = null;
+		boolean superExtendsStyle = true;
+		String applyMethodName = "apply";
+		
+		if (fieldDecl.vartype instanceof JCPrimitiveTypeTree) {
+			TypeKind kind = ((JCPrimitiveTypeTree) fieldDecl.vartype).getPrimitiveTypeKind();
+			if (kind == TypeKind.CHAR) {
+				requiredCast = Javac.CTC_CHAR;
+				functionalInterfaceName = NAME_JUF_INTOP;
+			} else if (kind == TypeKind.SHORT) {
+				requiredCast = Javac.CTC_SHORT;
+				functionalInterfaceName = NAME_JUF_INTOP;
+			} else if (kind == TypeKind.BYTE) {
+				requiredCast = Javac.CTC_BYTE;
+				functionalInterfaceName = NAME_JUF_INTOP;
+			} else if (kind == TypeKind.INT) {
+				functionalInterfaceName = NAME_JUF_INTOP;
+			} else if (kind == TypeKind.LONG) {
+				functionalInterfaceName = NAME_JUF_LONGOP;
+			} else if (kind == TypeKind.FLOAT) {
+				functionalInterfaceName = NAME_JUF_DOUBLEOP;
+				requiredCast = Javac.CTC_FLOAT;
+			} else if (kind == TypeKind.DOUBLE) {
+				functionalInterfaceName = NAME_JUF_DOUBLEOP;
+			} else if (kind == TypeKind.BOOLEAN) {
+				functionalInterfaceName = NAME_JUF_OP;
+				parameterizer = JavacHandlerUtil.genJavaLangTypeRef(field, "Boolean");
+				superExtendsStyle = false;
+			}
+		}
+		if (functionalInterfaceName == null) {
+			functionalInterfaceName = NAME_JUF_FUNCTION;
+			parameterizer = cloneType(maker, fieldDecl.vartype, source.get(), field.getContext());
+		}
+		if (functionalInterfaceName == NAME_JUF_INTOP) applyMethodName = "applyAsInt";
+		if (functionalInterfaceName == NAME_JUF_LONGOP) applyMethodName = "applyAsLong";
+		if (functionalInterfaceName == NAME_JUF_DOUBLEOP) applyMethodName = "applyAsDouble";
+		
+		JCExpression varType = chainDots(field, functionalInterfaceName);
+		if (parameterizer != null && superExtendsStyle) {
+			JCExpression parameterizer1 = parameterizer;
+			JCExpression parameterizer2 = cloneType(maker, parameterizer, source.get(), field.getContext());
+			// TODO: Apply copyable annotations to 'parameterizer' and 'parameterizer2'.
+			JCExpression arg1 = maker.Wildcard(maker.TypeBoundKind(BoundKind.SUPER), parameterizer1);
+			JCExpression arg2 = maker.Wildcard(maker.TypeBoundKind(BoundKind.EXTENDS), parameterizer2);
+			varType = maker.TypeApply(varType, List.of(arg1, arg2));
+		}
+		if (parameterizer != null && !superExtendsStyle) {
+			varType = maker.TypeApply(varType, List.of(parameterizer));
+		}
+		Name paramName = field.toName("transformer");
+		
+		JCVariableDecl param = maker.VarDef(maker.Modifiers(flags), paramName, varType, null);
+		
+		if (!makeAbstract) {
+			ListBuffer<JCStatement> statements = new ListBuffer<JCStatement>();
+			
+			JCExpression selfType = cloneSelfType(field);
+			if (selfType == null) return null;
+			
+			ListBuffer<JCExpression> args = new ListBuffer<JCExpression>();
+			for (JavacNode child : field.up().down()) {
+				if (child.getKind() != Kind.FIELD) continue;
+				JCVariableDecl childDecl = (JCVariableDecl) child.get();
+				// Skip fields that start with $
+				if (childDecl.name.toString().startsWith("$")) continue;
+				long fieldFlags = childDecl.mods.flags;
+				// Skip static fields.
+				if ((fieldFlags & Flags.STATIC) != 0) continue;
+				// Skip initialized final fields.
+				if (((fieldFlags & Flags.FINAL) != 0) && childDecl.init != null) continue;
+				if (child.get() == field.get()) {
+					JCExpression invoke = maker.Apply(List.<JCExpression>nil(), maker.Select(maker.Ident(paramName), field.toName(applyMethodName)), List.<JCExpression>of(createFieldAccessor(maker, child, FieldAccess.ALWAYS_FIELD)));
+					if (requiredCast != null) invoke = maker.TypeCast(maker.TypeIdent(requiredCast), invoke);
+					args.append(invoke);
+				} else {
+					args.append(createFieldAccessor(maker, child, FieldAccess.ALWAYS_FIELD));
+				}
+			}
+			
+			JCNewClass newClass = maker.NewClass(null, List.<JCExpression>nil(), selfType, args.toList(), null);
+			JCReturn returnStatement = maker.Return(newClass);
+			
+			statements.append(returnStatement);
+			
+			methodBody = maker.Block(0, statements.toList());
+		}
+		List<JCTypeParameter> methodGenericParams = List.nil();
+		List<JCVariableDecl> parameters = List.of(param);
+		List<JCExpression> throwsClauses = List.nil();
+		JCExpression annotationMethodDefaultValue = null;
+		
+		List<JCAnnotation> annsOnMethod = copyAnnotations(onMethod);
+		CheckerFrameworkVersion checkerFramework = getCheckerFrameworkVersion(source);
+		if (checkerFramework.generateSideEffectFree()) annsOnMethod = annsOnMethod.prepend(maker.Annotation(genTypeRef(source, CheckerFrameworkVersion.NAME__SIDE_EFFECT_FREE), List.<JCExpression>nil()));
+		
+		if (isFieldDeprecated(field)) annsOnMethod = annsOnMethod.prepend(maker.Annotation(genJavaLangTypeRef(field, "Deprecated"), List.<JCExpression>nil()));
+		
+		if (makeAbstract) access = access | Flags.ABSTRACT;
+		createRelevantNonNullAnnotation(source, param);
+		JCMethodDecl decl = recursiveSetGeneratedBy(maker.MethodDef(maker.Modifiers(access, annsOnMethod), methodName, returnType,
+			methodGenericParams, parameters, throwsClauses, methodBody, annotationMethodDefaultValue), source.get(), field.getContext());
+		copyJavadoc(field, decl, CopyJavadoc.WITH_BY);
+		createRelevantNonNullAnnotation(source, decl);
+		return decl;
+	}
+}

src/core/lombok/javac/handlers/JavacHandlerUtil.java

@@ -558,7 +558,7 @@ public class JavacHandlerUtil {
 	
 	/**
 	 * Translates the given field into all possible getter names.
-	 * Convenient wrapper around {@link TransformationsUtil#toAllGetterNames(lombok.core.AnnotationValues, CharSequence, boolean)}.
+	 * Convenient wrapper around {@link HandlerUtil#toAllGetterNames(lombok.core.AnnotationValues, CharSequence, boolean)}.
 	 */
 	public static java.util.List<String> toAllGetterNames(JavacNode field) {
 		return HandlerUtil.toAllGetterNames(field.getAst(), getAccessorsForField(field), field.getName(), isBoolean(field));
@@ -567,7 +567,7 @@ public class JavacHandlerUtil {
 	/**
 	 * @return the likely getter name for the stated field. (e.g. private boolean foo; to isFoo).
 	 * 
-	 * Convenient wrapper around {@link TransformationsUtil#toGetterName(lombok.core.AnnotationValues, CharSequence, boolean)}.
+	 * Convenient wrapper around {@link HandlerUtil#toGetterName(lombok.core.AnnotationValues, CharSequence, boolean)}.
 	 */
 	public static String toGetterName(JavacNode field) {
 		return HandlerUtil.toGetterName(field.getAst(), getAccessorsForField(field), field.getName(), isBoolean(field));
@@ -575,7 +575,7 @@ public class JavacHandlerUtil {
 	
 	/**
 	 * Translates the given field into all possible setter names.
-	 * Convenient wrapper around {@link TransformationsUtil#toAllSetterNames(lombok.core.AnnotationValues, CharSequence, boolean)}.
+	 * Convenient wrapper around {@link HandlerUtil#toAllSetterNames(lombok.core.AnnotationValues, CharSequence, boolean)}.
 	 */
 	public static java.util.List<String> toAllSetterNames(JavacNode field) {
 		return HandlerUtil.toAllSetterNames(field.getAst(), getAccessorsForField(field), field.getName(), isBoolean(field));
@@ -584,7 +584,7 @@ public class JavacHandlerUtil {
 	/**
 	 * @return the likely setter name for the stated field. (e.g. private boolean foo; to setFoo).
 	 * 
-	 * Convenient wrapper around {@link TransformationsUtil#toSetterName(lombok.core.AnnotationValues, CharSequence, boolean)}.
+	 * Convenient wrapper around {@link HandlerUtil#toSetterName(lombok.core.AnnotationValues, CharSequence, boolean)}.
 	 */
 	public static String toSetterName(JavacNode field) {
 		return HandlerUtil.toSetterName(field.getAst(), getAccessorsForField(field), field.getName(), isBoolean(field));
@@ -592,21 +592,38 @@ public class JavacHandlerUtil {
 	
 	/**
 	 * Translates the given field into all possible with names.
-	 * Convenient wrapper around {@link TransformationsUtil#toAllWithNames(lombok.core.AnnotationValues, CharSequence, boolean)}.
+	 * Convenient wrapper around {@link HandlerUtil#toAllWithNames(lombok.core.AnnotationValues, CharSequence, boolean)}.
 	 */
 	public static java.util.List<String> toAllWithNames(JavacNode field) {
 		return HandlerUtil.toAllWithNames(field.getAst(), getAccessorsForField(field), field.getName(), isBoolean(field));
 	}
 	
+	/**
+	 * Translates the given field into all possible withBy names.
+	 * Convenient wrapper around {@link HandlerUtil#toAllWithByNames(lombok.core.AnnotationValues, CharSequence, boolean)}.
+	 */
+	public static java.util.List<String> toAllWithByNames(JavacNode field) {
+		return HandlerUtil.toAllWithByNames(field.getAst(), getAccessorsForField(field), field.getName(), isBoolean(field));
+	}
+	
 	/**
 	 * @return the likely with name for the stated field. (e.g. private boolean foo; to withFoo).
 	 * 
-	 * Convenient wrapper around {@link TransformationsUtil#toWithName(lombok.core.AnnotationValues, CharSequence, boolean)}.
+	 * Convenient wrapper around {@link HandlerUtil#toWithName(lombok.core.AnnotationValues, CharSequence, boolean)}.
 	 */
 	public static String toWithName(JavacNode field) {
 		return HandlerUtil.toWithName(field.getAst(), getAccessorsForField(field), field.getName(), isBoolean(field));
 	}
 	
+	/**
+	 * @return the likely withBy name for the stated field. (e.g. private boolean foo; to withFooBy).
+	 * 
+	 * Convenient wrapper around {@link HandlerUtil#toWithByName(lombok.core.AnnotationValues, CharSequence, boolean)}.
+	 */
+	public static String toWithByName(JavacNode field) {
+		return HandlerUtil.toWithByName(field.getAst(), getAccessorsForField(field), field.getName(), isBoolean(field));
+	}
+	
 	/**
 	 * When generating a setter, the setter either returns void (beanspec) or Self (fluent).
 	 * This method scans for the {@code Accessors} annotation to figure that out.
@@ -1997,6 +2014,11 @@ public class JavacHandlerUtil {
 			@Override public String apply(final JCCompilationUnit cu, final JavacNode node) {
 				return addReturnsUpdatedSelfIfNeeded(applySetter(cu, node, "WITH|WITHER"));
 			}
+		},
+		WITH_BY {
+			@Override public String apply(final JCCompilationUnit cu, final JavacNode node) {
+				return applySetter(cu, node, "WITHBY|WITH_BY");
+			}
 		};
 		
 		public abstract String apply(final JCCompilationUnit cu, final JavacNode node);

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

@@ -0,0 +1,13 @@
+import java.util.List;
+public class WithByNullAnnos {
+	final List<String> test;
+	@java.lang.SuppressWarnings("all")
+	public WithByNullAnnos(final List<String> test) {
+		this.test = test;
+	}
+	@org.checkerframework.checker.nullness.qual.NonNull
+	@java.lang.SuppressWarnings("all")
+	public WithByNullAnnos withTestBy(final java.util.function.@org.checkerframework.checker.nullness.qual.NonNull Function<? super List<String>, ? extends List<String>> transformer) {
+		return new WithByNullAnnos(transformer.apply(this.test));
+	}
+}

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

@@ -0,0 +1,62 @@
+public class WithByTypes<T> {
+	private final int a;
+	private final long b;
+	private final short c;
+	private final char d;
+	private final byte e;
+	private final double f;
+	private final float g;
+	private final boolean h;
+	private final T i;
+	public static void example() {
+		new WithByTypes<String>(0, 0, (short) 0, ' ', (byte) 0, 0.0, 0.0F, true, "").withHBy(x -> !x).withFBy(x -> x + 0.5);
+	}
+	@java.lang.SuppressWarnings("all")
+	public WithByTypes(final int a, final long b, final short c, final char d, final byte e, final double f, final float g, final boolean h, final T i) {
+		this.a = a;
+		this.b = b;
+		this.c = c;
+		this.d = d;
+		this.e = e;
+		this.f = f;
+		this.g = g;
+		this.h = h;
+		this.i = i;
+	}
+	@java.lang.SuppressWarnings("all")
+	public WithByTypes<T> withABy(final java.util.function.IntUnaryOperator transformer) {
+		return new WithByTypes<T>(transformer.applyAsInt(this.a), this.b, this.c, this.d, this.e, this.f, this.g, this.h, this.i);
+	}
+	@java.lang.SuppressWarnings("all")
+	public WithByTypes<T> withBBy(final java.util.function.LongUnaryOperator transformer) {
+		return new WithByTypes<T>(this.a, transformer.applyAsLong(this.b), this.c, this.d, this.e, this.f, this.g, this.h, this.i);
+	}
+	@java.lang.SuppressWarnings("all")
+	public WithByTypes<T> withCBy(final java.util.function.IntUnaryOperator transformer) {
+		return new WithByTypes<T>(this.a, this.b, (short) transformer.applyAsInt(this.c), this.d, this.e, this.f, this.g, this.h, this.i);
+	}
+	@java.lang.SuppressWarnings("all")
+	public WithByTypes<T> withDBy(final java.util.function.IntUnaryOperator transformer) {
+		return new WithByTypes<T>(this.a, this.b, this.c, (char) transformer.applyAsInt(this.d), this.e, this.f, this.g, this.h, this.i);
+	}
+	@java.lang.SuppressWarnings("all")
+	public WithByTypes<T> withEBy(final java.util.function.IntUnaryOperator transformer) {
+		return new WithByTypes<T>(this.a, this.b, this.c, this.d, (byte) transformer.applyAsInt(this.e), this.f, this.g, this.h, this.i);
+	}
+	@java.lang.SuppressWarnings("all")
+	public WithByTypes<T> withFBy(final java.util.function.DoubleUnaryOperator transformer) {
+		return new WithByTypes<T>(this.a, this.b, this.c, this.d, this.e, transformer.applyAsDouble(this.f), this.g, this.h, this.i);
+	}
+	@java.lang.SuppressWarnings("all")
+	public WithByTypes<T> withGBy(final java.util.function.DoubleUnaryOperator transformer) {
+		return new WithByTypes<T>(this.a, this.b, this.c, this.d, this.e, this.f, (float) transformer.applyAsDouble(this.g), this.h, this.i);
+	}
+	@java.lang.SuppressWarnings("all")
+	public WithByTypes<T> withHBy(final java.util.function.UnaryOperator<java.lang.Boolean> transformer) {
+		return new WithByTypes<T>(this.a, this.b, this.c, this.d, this.e, this.f, this.g, transformer.apply(this.h), this.i);
+	}
+	@java.lang.SuppressWarnings("all")
+	public WithByTypes<T> withIBy(final java.util.function.Function<? super T, ? extends T> transformer) {
+		return new WithByTypes<T>(this.a, this.b, this.c, this.d, this.e, this.f, this.g, this.h, transformer.apply(this.i));
+	}
+}

test/transform/resource/before/WithByNullAnnos.java

@@ -0,0 +1,6 @@
+//CONF: lombok.addNullAnnotations=checkerframework
+import java.util.List;
+@lombok.RequiredArgsConstructor
+public class WithByNullAnnos {
+	@lombok.experimental.WithBy final List<String> test;
+}

test/transform/resource/before/WithByTypes.java

@@ -0,0 +1,18 @@
+@lombok.RequiredArgsConstructor
+@lombok.experimental.FieldDefaults(level = lombok.AccessLevel.PRIVATE, makeFinal = true)
+@lombok.experimental.WithBy
+public class WithByTypes<T> {
+	int a;
+	long b;
+	short c;
+	char d;
+	byte e;
+	double f;
+	float g;
+	boolean h;
+	T i;
+	
+	public static void example() {
+		new WithByTypes<String>(0, 0, (short) 0, ' ', (byte) 0, 0.0, 0.0F, true, "").withHBy(x -> !x).withFBy(x -> x + 0.5);
+	}
+}