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Break out a helper class from GenerateVisitor annotation processor. #3060
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274 changes: 274 additions & 0 deletions
274
...ions/src/main/java/com/apple/foundationdb/annotation/GenerateVisitorAnnotationHelper.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,274 @@ | ||
| /* | ||
| * GenerateVisitorAnnotationHelper.java | ||
| * | ||
| * This source file is part of the FoundationDB open source project | ||
| * | ||
| * Copyright 2015-2025 Apple Inc. and the FoundationDB project 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 | ||
| * | ||
| * http://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 com.apple.foundationdb.annotation; | ||
|
|
||
| import com.squareup.javapoet.AnnotationSpec; | ||
| import com.squareup.javapoet.ClassName; | ||
| import com.squareup.javapoet.CodeBlock; | ||
| import com.squareup.javapoet.FieldSpec; | ||
| import com.squareup.javapoet.JavaFile; | ||
| import com.squareup.javapoet.MethodSpec; | ||
| import com.squareup.javapoet.ParameterSpec; | ||
| import com.squareup.javapoet.ParameterizedTypeName; | ||
| import com.squareup.javapoet.TypeName; | ||
| import com.squareup.javapoet.TypeSpec; | ||
| import com.squareup.javapoet.TypeVariableName; | ||
| import com.squareup.javapoet.WildcardTypeName; | ||
|
|
||
| import javax.annotation.Nonnull; | ||
| import javax.annotation.processing.Filer; | ||
| import javax.annotation.processing.Messager; | ||
| import javax.annotation.processing.ProcessingEnvironment; | ||
| import javax.annotation.processing.RoundEnvironment; | ||
| import javax.lang.model.element.Element; | ||
| import javax.lang.model.element.ElementKind; | ||
| import javax.lang.model.element.Modifier; | ||
| import javax.lang.model.element.PackageElement; | ||
| import javax.lang.model.element.TypeElement; | ||
| import javax.lang.model.type.TypeKind; | ||
| import javax.lang.model.type.TypeMirror; | ||
| import javax.lang.model.util.Types; | ||
| import javax.tools.Diagnostic; | ||
| import java.io.IOException; | ||
| import java.util.List; | ||
| import java.util.Locale; | ||
| import java.util.Map; | ||
| import java.util.Objects; | ||
| import java.util.Set; | ||
| import java.util.function.BiFunction; | ||
| import java.util.stream.Collectors; | ||
|
|
||
| /** | ||
| * A separate class to support (@link GenerateVisitorAnnotationProcessor) so that dependency on javapoet does not leak to anyone | ||
| * just service loading all annotation processors in the class path. | ||
| */ | ||
| @SuppressWarnings("PMD.GuardLogStatement") // confused by error invocation | ||
| class GenerateVisitorAnnotationHelper { | ||
| private static final String parameterName = "element"; | ||
|
|
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| private GenerateVisitorAnnotationHelper() { | ||
| } | ||
|
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| static boolean process(final ProcessingEnvironment processingEnv, Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) { | ||
| final var elementUtils = processingEnv.getElementUtils(); | ||
| final var typeUtils = processingEnv.getTypeUtils(); | ||
| final var messager = processingEnv.getMessager(); | ||
| final var filer = processingEnv.getFiler(); | ||
|
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| for (final Element annotatedElement : roundEnv.getElementsAnnotatedWith(GenerateVisitor.class)) { | ||
| if (!annotatedElement.getKind().isClass() && !annotatedElement.getKind().isInterface()) { | ||
| error(messager, annotatedElement, "only classes and interfaces can be annotated with %s", GenerateVisitor.class.getSimpleName()); | ||
| return true; | ||
| } | ||
|
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| final var rootTypeElement = (TypeElement)annotatedElement; | ||
|
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| final var moduleElement = elementUtils.getModuleOf(annotatedElement); | ||
| if (moduleElement == null) { | ||
| error(messager, annotatedElement, "cannot annotate class with %s in null-module", GenerateVisitor.class.getSimpleName()); | ||
| return true; | ||
| } | ||
|
|
||
| if (!isValidClass(rootTypeElement)) { | ||
| error(messager, | ||
| rootTypeElement, "The class %s cannot be annotated with this annotation.", | ||
| rootTypeElement.getQualifiedName().toString()); | ||
| return true; | ||
| } | ||
|
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| final var generateVisitor = annotatedElement.getAnnotation(GenerateVisitor.class); | ||
| final var rootTypeMirror = rootTypeElement.asType(); | ||
|
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| final var packageOfRoot = elementUtils.getPackageOf(rootTypeElement); | ||
| final var subClassTypeMirrors = moduleElement | ||
| .getEnclosedElements() | ||
| .stream() | ||
| .flatMap(packageElement -> packageElement.getEnclosedElements().stream()) | ||
| .filter(element -> element.getKind() == ElementKind.CLASS && | ||
| !element.getModifiers().contains(Modifier.ABSTRACT)) | ||
| .map(Element::asType) | ||
| .filter(mirror -> mirror.getKind() == TypeKind.DECLARED) | ||
| .filter(mirror -> typeUtils.isSubtype(mirror, rootTypeMirror)) | ||
| .collect(Collectors.toList()); | ||
|
|
||
| try { | ||
| generateCode(typeUtils, filer, generateVisitor, packageOfRoot, rootTypeElement, subClassTypeMirrors); | ||
| } catch (final Exception exception) { | ||
| Objects.requireNonNull(messager) | ||
| .printMessage(Diagnostic.Kind.ERROR, | ||
| "unable to generate visitor in " + packageOfRoot.getQualifiedName() + "[" + exception.getMessage() + "]"); | ||
| } | ||
| } | ||
|
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| return true; | ||
| } | ||
|
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| private static void generateCode(@Nonnull final Types typeUtils, | ||
| @Nonnull final Filer filer, | ||
| @Nonnull GenerateVisitor generateVisitor, | ||
| @Nonnull final PackageElement packageElement, | ||
| @Nonnull final TypeElement rootTypeElement, | ||
| @Nonnull final List<TypeMirror> subClassTypeMirrors) throws IOException { | ||
| final var rootTypeMirror = rootTypeElement.asType(); | ||
| final var interfaceName = rootTypeElement.getSimpleName() + generateVisitor.classSuffix(); | ||
| final var typeVariableName = TypeVariableName.get("T"); | ||
| final var defaultMethodName = generateVisitor.methodPrefix() + "Default"; | ||
|
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| generateInterface(typeUtils, filer, generateVisitor, packageElement, subClassTypeMirrors, rootTypeMirror, interfaceName, typeVariableName, defaultMethodName); | ||
|
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| final var className = rootTypeElement.getSimpleName() + generateVisitor.classSuffix() + "WithDefaults"; | ||
| generateImplementationWithDefaults(typeUtils, filer, generateVisitor, packageElement, subClassTypeMirrors, className, interfaceName, typeVariableName, defaultMethodName); | ||
| } | ||
|
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| private static void generateInterface(@Nonnull final Types typeUtils, | ||
| @Nonnull final Filer filer, | ||
| @Nonnull final GenerateVisitor generateVisitor, | ||
| @Nonnull final PackageElement packageElement, | ||
| @Nonnull final List<TypeMirror> subClassTypeMirrors, | ||
| @Nonnull final TypeMirror rootTypeMirror, | ||
| @Nonnull final String interfaceName, | ||
| @Nonnull final TypeVariableName typeVariableName, | ||
| @Nonnull final String defaultMethodName) throws IOException { | ||
| final TypeSpec.Builder typeBuilder = | ||
| TypeSpec.interfaceBuilder(interfaceName) | ||
| .addModifiers(Modifier.PUBLIC) | ||
| .addTypeVariable(typeVariableName); | ||
|
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||
| final var jumpMapBuilder = FieldSpec.builder(ParameterizedTypeName.get(ClassName.get(Map.class), | ||
| ParameterizedTypeName.get(ClassName.get(Class.class), WildcardTypeName.subtypeOf(Object.class)), | ||
| ParameterizedTypeName.get(ClassName.get(BiFunction.class), | ||
| ParameterizedTypeName.get(ClassName.get(packageElement.getQualifiedName().toString(), interfaceName), WildcardTypeName.subtypeOf(Object.class)), | ||
| TypeName.get(rootTypeMirror), | ||
| WildcardTypeName.subtypeOf(Object.class))), | ||
| "jumpMap", Modifier.PUBLIC, Modifier.STATIC, Modifier.FINAL); | ||
|
|
||
| final var initializerStrings = subClassTypeMirrors.stream() | ||
| .map(typeMirror -> { | ||
| final var typeElement = (TypeElement)typeUtils.asElement(typeMirror); | ||
| return "Map.entry(" + typeElement.getSimpleName() + ".class, (visitor, element) -> visitor." + methodNameOfVisitMethod(generateVisitor, typeElement) + "((" + typeElement.getSimpleName() + ")element))"; | ||
| }) | ||
| .collect(Collectors.joining(", \n")); | ||
|
|
||
| final var initializerBlock = CodeBlock.builder() | ||
| .add("$T.ofEntries(" + initializerStrings + ")", ClassName.get(Map.class)) | ||
| .build(); | ||
|
|
||
| typeBuilder.addField(jumpMapBuilder | ||
| .initializer(initializerBlock) | ||
| .build()); | ||
|
|
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| for (final var typeMirror : subClassTypeMirrors) { | ||
| final var typeElement = (TypeElement)typeUtils.asElement(typeMirror); | ||
| final var methodName = methodNameOfVisitMethod(generateVisitor, typeElement); | ||
| final MethodSpec.Builder specificVisitMethodBuilder = | ||
| MethodSpec | ||
| .methodBuilder(methodName) | ||
| .addModifiers(Modifier.PUBLIC, Modifier.ABSTRACT) | ||
| .addAnnotation(Nonnull.class) | ||
| .addParameter(ParameterSpec.builder(TypeName.get(typeMirror), parameterName).addAnnotation(Nonnull.class).build()) | ||
| .returns(typeVariableName); | ||
| typeBuilder.addMethod(specificVisitMethodBuilder.build()); | ||
| } | ||
|
|
||
| final MethodSpec.Builder visitDefaultMethodBuilder = | ||
| MethodSpec | ||
| .methodBuilder(defaultMethodName) | ||
| .addModifiers(Modifier.PUBLIC, Modifier.ABSTRACT) | ||
| .addAnnotation(Nonnull.class) | ||
| .addParameter(ParameterSpec.builder(TypeName.get(rootTypeMirror), parameterName).addAnnotation(Nonnull.class).build()) | ||
| .returns(typeVariableName); | ||
| typeBuilder.addMethod(visitDefaultMethodBuilder.build()); | ||
|
|
||
| final MethodSpec.Builder visitMethodBuilder = | ||
| MethodSpec | ||
| .methodBuilder(generateVisitor.methodPrefix()) | ||
| .addModifiers(Modifier.PUBLIC, Modifier.DEFAULT) | ||
| .addAnnotation(AnnotationSpec.builder(SuppressWarnings.class).addMember("value", "$S", "unchecked").build()) | ||
| .addParameter(ParameterSpec.builder(TypeName.get(rootTypeMirror), parameterName).addAnnotation(Nonnull.class).build()) | ||
| .returns(typeVariableName) | ||
| .addCode(CodeBlock.builder() | ||
| .addStatement("final var visitFn = jumpMap.get(" + parameterName + ".getClass())") | ||
| .addStatement("return visitFn == null ? visitDefault(" + parameterName + ") : (" + typeVariableName + ")visitFn.apply(this, " + parameterName + ")") | ||
| .build()); | ||
| typeBuilder.addMethod(visitMethodBuilder.build()); | ||
|
|
||
| JavaFile.builder(packageElement.getQualifiedName().toString(), typeBuilder.build()) | ||
| .skipJavaLangImports(true) | ||
| .build() | ||
| .writeTo(Objects.requireNonNull(filer)); | ||
| } | ||
|
|
||
| private static void generateImplementationWithDefaults(@Nonnull final Types typeUtils, | ||
| @Nonnull final Filer filer, | ||
| @Nonnull final GenerateVisitor generateVisitor, | ||
| @Nonnull final PackageElement packageElement, | ||
| @Nonnull final List<TypeMirror> subClassTypeMirrors, | ||
| @Nonnull final String className, | ||
| @Nonnull final String interfaceName, | ||
| @Nonnull final TypeVariableName typeVariableName, | ||
| @Nonnull final String defaultMethodName) throws IOException { | ||
| final TypeSpec.Builder typeBuilder = | ||
| TypeSpec.interfaceBuilder(className) | ||
| .addModifiers(Modifier.PUBLIC) | ||
| .addTypeVariable(typeVariableName) | ||
| .addSuperinterface(ParameterizedTypeName.get(ClassName.get(packageElement.getQualifiedName().toString(), interfaceName), typeVariableName)); | ||
|
|
||
| for (final var typeMirror : subClassTypeMirrors) { | ||
| final var typeElement = (TypeElement)typeUtils.asElement(typeMirror); | ||
| final var methodName = methodNameOfVisitMethod(generateVisitor, typeElement); | ||
| final MethodSpec.Builder specificVisitMethodBuilder = | ||
| MethodSpec | ||
| .methodBuilder(methodName) | ||
| .addModifiers(Modifier.PUBLIC, Modifier.DEFAULT) | ||
| .addAnnotation(Nonnull.class) | ||
| .addAnnotation(Override.class) | ||
| .addParameter(ParameterSpec.builder(TypeName.get(typeMirror), parameterName).addAnnotation(Nonnull.class).build()) | ||
| .returns(typeVariableName) | ||
| .addCode(CodeBlock.builder() | ||
| .addStatement("return " + defaultMethodName + "(" + parameterName + ")") | ||
| .build()); | ||
| typeBuilder.addMethod(specificVisitMethodBuilder.build()); | ||
| } | ||
|
|
||
| JavaFile.builder(packageElement.getQualifiedName().toString(), typeBuilder.build()) | ||
| .skipJavaLangImports(true) | ||
| .build() | ||
| .writeTo(Objects.requireNonNull(filer)); | ||
| } | ||
|
|
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| private static String methodNameOfVisitMethod(@Nonnull final GenerateVisitor generateVisitor, @Nonnull TypeElement typeElement) { | ||
| return generateVisitor.methodPrefix() + typeElement.getSimpleName().toString().replace(generateVisitor.stripPrefix(), ""); | ||
| } | ||
|
|
||
| @SuppressWarnings("BooleanMethodIsAlwaysInverted") | ||
| private static boolean isValidClass(final TypeElement annotatedClassElement) { | ||
| return annotatedClassElement.getModifiers().contains(Modifier.PUBLIC); | ||
| } | ||
|
|
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| private static void error(final Messager messager, | ||
| final Element e, | ||
| final String msg, | ||
| final Object... args) { | ||
| Objects.requireNonNull(messager).printMessage(Diagnostic.Kind.ERROR, | ||
| String.format(Locale.ROOT, msg, args), | ||
| e); | ||
| } | ||
| } | ||
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There should probably be a javadoc comment here explaining why this is a separate class from
GenerateVisitorAnnotationProcessor, mostly to avoid us from doing some "harmless refactoring" in the future and putting the two classes back together again. (Likewise, we should call this out in the release notes.)