java/dagger/internal/codegen/AbstractMethodModifiableBindingExpression.java

/*
 * Copyright (C) 2018 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;

import static dagger.internal.codegen.RequestKinds.requestTypeName;
import static javax.lang.model.element.Modifier.ABSTRACT;
import static javax.lang.model.element.Modifier.PUBLIC;

import com.squareup.javapoet.ClassName;
import com.squareup.javapoet.CodeBlock;
import com.squareup.javapoet.MethodSpec;
import com.squareup.javapoet.TypeName;
import dagger.model.Key;
import dagger.model.RequestKind;

/**
 * A {@link BindingExpression} that invokes a method that encapsulates a binding that cannot be
 * satisfied when generating the abstract base class implementation of a subcomponent. The
 * (unimplemented) method is added to the {@link GeneratedComponentModel} when the dependency
 * expression is requested. The method is overridden when generating the implementation of an
 * ancestor component.
 */
abstract class AbstractMethodModifiableBindingExpression extends BindingExpression {
  private final GeneratedComponentModel generatedComponentModel;
  private final ModifiableBindingType modifiableBindingType;
  private final Key key;
  private final RequestKind kind;
  private String methodName;

  AbstractMethodModifiableBindingExpression(
      GeneratedComponentModel generatedComponentModel,
      ModifiableBindingType modifiableBindingType,
      Key key,
      RequestKind kind) {
    this.generatedComponentModel = generatedComponentModel;
    this.modifiableBindingType = modifiableBindingType;
    this.key = key;
    this.kind = kind;
  }

  @Override
  final Expression getDependencyExpression(ClassName requestingClass) {
    addUnimplementedMethod();
    return Expression.create(key.type(), CodeBlock.of("$L()", methodName));
  }

  private void addUnimplementedMethod() {
    if (methodName == null) {
      // Only add the method once in case of repeated references to the missing binding.
      methodName = chooseMethodName();
      generatedComponentModel.addModifiableBindingMethod(
          modifiableBindingType,
          key,
          kind,
          MethodSpec.methodBuilder(methodName)
              .addModifiers(PUBLIC, ABSTRACT)
              .returns(requestTypeName(kind, TypeName.get(key.type())))
              .build());
    }
  }

  /** Returns a unique 'getter' method name for the current component. */
  abstract String chooseMethodName();
}