factory/src/main/java/com/google/auto/factory/processor/ProvidedChecker.java

/*
 * Copyright 2013 Google LLC
 *
 * 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.auto.factory.processor;

import static com.google.auto.common.MoreElements.isAnnotationPresent;
import static com.google.common.base.Preconditions.checkArgument;
import static javax.tools.Diagnostic.Kind.ERROR;

import com.google.auto.factory.AutoFactory;
import com.google.auto.factory.Provided;
import javax.annotation.processing.Messager;
import javax.lang.model.element.Element;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.element.VariableElement;
import javax.lang.model.util.ElementKindVisitor6;
import org.checkerframework.checker.nullness.qual.Nullable;

final class ProvidedChecker {
  private final Messager messager;

  ProvidedChecker(Messager messager) {
    this.messager = messager;
  }

  void checkProvidedParameter(Element element) {
    checkArgument(
        isAnnotationPresent(element, Provided.class), "%s not annoated with @Provided", element);
    element.accept(
        new ElementKindVisitor6<@Nullable Void, @Nullable Void>() {
          @Override
          protected @Nullable Void defaultAction(Element e, @Nullable Void p) {
            throw new AssertionError("Provided can only be applied to parameters");
          }

          @Override
          public @Nullable Void visitVariableAsParameter(
              VariableElement providedParameter, @Nullable Void p) {
            providedParameter
                .getEnclosingElement()
                .accept(
                    new ElementKindVisitor6<@Nullable Void, @Nullable Void>() {
                      @Override
                      protected @Nullable Void defaultAction(Element e, @Nullable Void p) {
                        raiseError(
                            providedParameter, "@%s may only be applied to constructor parameters");
                        return null;
                      }

                      @Override
                      public @Nullable Void visitExecutableAsConstructor(
                          ExecutableElement constructor, @Nullable Void p) {
                        if (!(annotatedWithAutoFactory(constructor)
                            || annotatedWithAutoFactory(constructor.getEnclosingElement()))) {
                          raiseError(
                              providedParameter,
                              "@%s may only be applied to constructors requesting an auto-factory");
                        }
                        return null;
                      }
                    },
                    p);
            return null;
          }
        },
        null);
  }

  private void raiseError(VariableElement providedParameter, String messageFormat) {
    messager.printMessage(
        ERROR,
        String.format(messageFormat, Provided.class.getSimpleName()),
        providedParameter,
        Mirrors.getAnnotationMirror(providedParameter, Provided.class).get());
  }

  private static boolean annotatedWithAutoFactory(Element e) {
    return isAnnotationPresent(e, AutoFactory.class);
  }
}