| // Copyright 2017 The Bazel Authors. All rights reserved. |
| // |
| // 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.google.devtools.build.lib.analysis.starlark.annotations.processor; |
| |
| import com.google.devtools.build.lib.analysis.starlark.annotations.StarlarkConfigurationField; |
| import java.util.Set; |
| import javax.annotation.processing.AbstractProcessor; |
| import javax.annotation.processing.Messager; |
| import javax.annotation.processing.ProcessingEnvironment; |
| import javax.annotation.processing.RoundEnvironment; |
| import javax.annotation.processing.SupportedAnnotationTypes; |
| import javax.lang.model.SourceVersion; |
| import javax.lang.model.element.Element; |
| import javax.lang.model.element.ElementKind; |
| import javax.lang.model.element.ExecutableElement; |
| import javax.lang.model.element.Modifier; |
| import javax.lang.model.element.TypeElement; |
| import javax.lang.model.util.Elements; |
| import javax.lang.model.util.Types; |
| import javax.tools.Diagnostic; |
| |
| /** |
| * Annotation processor for {@link StarlarkConfigurationField}. |
| * |
| * <p>Checks the following invariants about {@link StarlarkConfigurationField}-annotated methods: |
| * |
| * <ul> |
| * <li>The annotated method must be on a configuration fragment. |
| * <li>The method must have return type Label. |
| * <li>The method must be public. |
| * <li>The method must have zero arguments. |
| * <li>The method must not throw exceptions. |
| * </ul> |
| * |
| * <p>These properties can be relied upon at runtime without additional checks. |
| */ |
| @SupportedAnnotationTypes({ |
| "com.google.devtools.build.lib.analysis.starlark.annotations.StarlarkConfigurationField" |
| }) |
| public final class StarlarkConfigurationFieldProcessor extends AbstractProcessor { |
| |
| private Messager messager; |
| private Types typeUtils; |
| private Elements elementUtils; |
| private TypeElement labelType; |
| private TypeElement configurationFragmentType; |
| |
| @Override |
| public SourceVersion getSupportedSourceVersion() { |
| return SourceVersion.latestSupported(); |
| } |
| |
| @Override |
| public synchronized void init(ProcessingEnvironment processingEnv) { |
| super.init(processingEnv); |
| messager = processingEnv.getMessager(); |
| typeUtils = processingEnv.getTypeUtils(); |
| elementUtils = processingEnv.getElementUtils(); |
| labelType = |
| elementUtils.getTypeElement("com.google.devtools.build.lib.cmdline.Label"); |
| configurationFragmentType = |
| elementUtils.getTypeElement("com.google.devtools.build.lib.analysis.config.Fragment"); |
| } |
| |
| @Override |
| public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) { |
| for (Element element : roundEnv.getElementsAnnotatedWith(StarlarkConfigurationField.class)) { |
| // Only methods are annotated with StarlarkConfigurationField. This is verified by the |
| // @Target(ElementType.METHOD) annotation. |
| ExecutableElement methodElement = (ExecutableElement) element; |
| |
| if (!isMethodOfStarlarkExposedConfigurationFragment(methodElement)) { |
| error(methodElement, "@StarlarkConfigurationField annotated methods must be methods " |
| + "of configuration fragments."); |
| } |
| // If labelType is null, then Label isn't even included |
| // in the current build, so the method clearly does not return it. |
| if (labelType == null |
| || !typeUtils.isSameType(methodElement.getReturnType(), labelType.asType())) { |
| error(methodElement, "@StarlarkConfigurationField annotated methods must return Label."); |
| } |
| if (!methodElement.getModifiers().contains(Modifier.PUBLIC)) { |
| error(methodElement, "@StarlarkConfigurationField annotated methods must be public."); |
| } |
| if (!methodElement.getParameters().isEmpty()) { |
| error(methodElement, |
| "@StarlarkConfigurationField annotated methods must have zero arguments."); |
| } |
| if (!methodElement.getThrownTypes().isEmpty()) { |
| error(methodElement, |
| "@StarlarkConfigurationField annotated must not throw exceptions."); |
| } |
| } |
| return false; |
| } |
| |
| private boolean isMethodOfStarlarkExposedConfigurationFragment( |
| ExecutableElement methodElement) { |
| |
| if (methodElement.getEnclosingElement().getKind() != ElementKind.CLASS) { |
| return false; |
| } |
| Element classElement = methodElement.getEnclosingElement(); |
| // If configurationFragmentType is null, then BuildConfiguration.Fragment isn't even included |
| // in the current build, so the class clearly does not depend on it. |
| if (configurationFragmentType == null |
| || !typeUtils.isAssignable(classElement.asType(), configurationFragmentType.asType())) { |
| return false; |
| } |
| |
| return true; |
| } |
| |
| /** |
| * Prints an error message & fails the compilation. |
| * |
| * @param e The element which has caused the error. Can be null |
| * @param msg The error message |
| */ |
| public void error(Element e, String msg) { |
| messager.printMessage(Diagnostic.Kind.ERROR, msg, e); |
| } |
| } |