java/dagger/internal/codegen/binding/BindingDeclaration.java

/*
 * Copyright (C) 2015 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.binding;

import static dagger.internal.codegen.extension.Optionals.emptiesLast;
import static java.util.Comparator.comparing;

import dagger.internal.codegen.langmodel.DaggerElements;
import dagger.model.BindingKind;
import dagger.model.Key;
import java.util.Comparator;
import java.util.Optional;
import javax.lang.model.element.Element;
import javax.lang.model.element.TypeElement;

/** An object that declares or specifies a binding. */
public abstract class BindingDeclaration {
  /**
   * A comparator that compares binding declarations with elements.
   *
   * <p>Compares, in order:
   *
   * <ol>
   *   <li>Contributing module or enclosing type name
   *   <li>Binding element's simple name
   *   <li>Binding element's type
   * </ol>
   *
   * Any binding declarations without elements are last.
   */
  public static final Comparator<BindingDeclaration> COMPARATOR =
      comparing(
              (BindingDeclaration declaration) ->
                  declaration.contributingModule().isPresent()
                      ? declaration.contributingModule()
                      : declaration.bindingTypeElement(),
              emptiesLast(comparing((TypeElement type) -> type.getQualifiedName().toString())))
          .thenComparing(
              (BindingDeclaration declaration) -> declaration.bindingElement(),
              emptiesLast(
                  comparing((Element element) -> element.getSimpleName().toString())
                      .thenComparing((Element element) -> element.asType().toString())));

  /** The {@link Key} of this declaration. */
  public abstract Key key();

  /**
   * The {@link Element} that declares this binding. Absent for {@linkplain BindingKind binding
   * kinds} that are not always declared by exactly one element.
   *
   * <p>For example, consider {@link BindingKind#MULTIBOUND_SET}. A component with many
   * {@code @IntoSet} bindings for the same key will have a synthetic binding that depends on all
   * contributions, but with no identifiying binding element. A {@code @Multibinds} method will also
   * contribute a synthetic binding, but since multiple {@code @Multibinds} methods can coexist in
   * the same component (and contribute to one single binding), it has no binding element.
   */
  public abstract Optional<Element> bindingElement();

  /**
   * The type enclosing the {@link #bindingElement()}, or {@link Optional#empty()} if {@link
   * #bindingElement()} is empty.
   */
  public final Optional<TypeElement> bindingTypeElement() {
    return bindingElement().map(DaggerElements::closestEnclosingTypeElement);
  }

  /**
   * The installed module class that contributed the {@link #bindingElement()}. May be a subclass of
   * the class that contains {@link #bindingElement()}. Absent if {@link #bindingElement()} is
   * empty.
   */
  public abstract Optional<TypeElement> contributingModule();
}