java/dagger/internal/codegen/javac/JavacPluginProcessingEnvironment.java

/*
 * Copyright (C) 2021 The Dagger 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 dagger.internal.codegen.javac;

import com.google.common.collect.ImmutableMap;
import java.util.Locale;
import javax.annotation.processing.Filer;
import javax.annotation.processing.Messager;
import javax.annotation.processing.ProcessingEnvironment;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.AnnotationMirror;
import javax.lang.model.element.AnnotationValue;
import javax.lang.model.element.Element;
import javax.lang.model.util.Elements;  // ALLOW_TYPES_ELEMENTS since in interface API
import javax.lang.model.util.Types;  // ALLOW_TYPES_ELEMENTS since in interface API
import javax.tools.Diagnostic;
import javax.tools.FileObject;
import javax.tools.JavaFileManager.Location;
import javax.tools.JavaFileObject;

/**
 * An implementation of {@link ProcessingEnvironment} that runs in a javac plugin environment.
 *
 * <p>This environment runs after the classes are already compiled, so parts of the {@link
 * ProcessingEnvironment} API like {@link Filer}, {@link Messager} don't make sense in this
 * environment, so they've been replaced with throwing and no-op implementations respectively.
 */
final class JavacPluginProcessingEnvironment implements ProcessingEnvironment {
  private final Elements elements;
  private final Types types;
  private final Filer filer = new ThrowingFiler();
  private final Messager messager = new NoopMessager();

  JavacPluginProcessingEnvironment(Elements elements, Types types) {
    this.elements = elements;
    this.types = types;
  }

  @Override
  public Elements getElementUtils() {
    return elements;
  }

  @Override
  public Types getTypeUtils() {
    return types;
  }

  @Override
  public Filer getFiler() {
    return filer;
  }

  @Override
  public Locale getLocale() {
    // Null means there's no locale in effect
    return null;
  }

  @Override
  public Messager getMessager() {
    return messager;
  }

  @Override
  public ImmutableMap<String, String> getOptions() {
    // TODO(erichang): You can technically parse options out of the context, but it is internal
    // implementation and unclear that any of the tools will ever be passing an option.
    return ImmutableMap.of();
  }

  @Override
  public SourceVersion getSourceVersion() {
    // This source version doesn't really matter because it is saying what version generated code
    // should adhere to, which there shouldn't be any because the Filer doesn't work.
    return SourceVersion.latestSupported();
  }

  private static final class ThrowingFiler implements Filer {
    @Override
    public JavaFileObject createClassFile(CharSequence name, Element... originatingElements) {
      throw new UnsupportedOperationException("Cannot use a Filer in this context");
    }

    @Override
    public FileObject createResource(
        Location location,
        CharSequence pkg,
        CharSequence relativeName,
        Element... originatingElements) {
      throw new UnsupportedOperationException("Cannot use a Filer in this context");
    }

    @Override
    public JavaFileObject createSourceFile(CharSequence name, Element... originatingElements) {
      throw new UnsupportedOperationException("Cannot use a Filer in this context");
    }

    @Override
    public FileObject getResource(Location location, CharSequence pkg, CharSequence relativeName) {
      throw new UnsupportedOperationException("Cannot use a Filer in this context");
    }
  }

  private static final class NoopMessager implements Messager {
    @Override
    public void printMessage(Diagnostic.Kind kind, CharSequence charSequence) {}

    @Override
    public void printMessage(Diagnostic.Kind kind, CharSequence charSequence, Element element) {}

    @Override
    public void printMessage(
        Diagnostic.Kind kind,
        CharSequence charSequence,
        Element element,
        AnnotationMirror annotationMirror) {}

    @Override
    public void printMessage(
        Diagnostic.Kind kind,
        CharSequence charSequence,
        Element element,
        AnnotationMirror annotationMirror,
        AnnotationValue annotationValue) {}
  }
}