BindingToUnqualifiedCommonType
This code declares a binding for a common value type without a Qualifier annotation.

Category
GUICE
Severity
WARNING
Maturity

The problem

Guice bindings are keyed by a pair of (optional Annotation, Type).

In most cirumstances, one doesn’t need the annotation, as there’s really just one active implementation:

bind(CoffeeMaker.class).to(RealCoffeeMaker.class);
...
@Inject Office(CoffeeMaker coffeeMaker) {}

However, in other circumstances, you want to bind a simple value (an integer, String, double, etc.). You should use a Qualifier annotation to allow you to get the right Integer back:

bindConstant(Integer.class).annotatedWith(HttpPort.class).to(80);
...
@Inject MyWebServer(@HttpPort Integer httpPort) {}

This works great, but if your integer binding doesn’t include a Qualifier, it just means that you can ask Guice for “the Integer”, and it will give you a value back:

bind(Integer.class).toInstance(80);
...
@Inject MyWebServer(Integer httpsPort) {}

To avoid confusion in these circumstances, please use a Qualifier annotation when binding simple value types.

Suppression

Suppress false positives by adding an @SuppressWarnings("BindingToUnqualifiedCommonType") annotation to the enclosing element.


Positive examples

BindingToUnqualifiedCommonTypePositiveCases.java

/*
 * Copyright 2016 Google Inc. 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.errorprone.bugpatterns.inject.guice.testdata;

import com.google.inject.AbstractModule;
import com.google.inject.Provides;

/** Tests for {@code BindingToUnqualifiedCommonType} */
public class BindingToUnqualifiedCommonTypePositiveCases {

  /** Regular module */
  class Module1 extends AbstractModule {
    @Override
    protected void configure() {
      // BUG: Diagnostic contains: BindingToUnqualifiedCommonType
      bind(Integer.class).toInstance(2);

      // BUG: Diagnostic contains: BindingToUnqualifiedCommonType
      bind(String.class).toInstance("Hello");

      // BUG: Diagnostic contains: BindingToUnqualifiedCommonType
      bind(Double.class).toProvider(() -> 42.0);

      // BUG: Diagnostic contains: BindingToUnqualifiedCommonType
      binder().bind(Long.class).toInstance(42L);
    }

    @Provides
    // BUG: Diagnostic contains: BindingToUnqualifiedCommonType
    int providesFoo() {
      return 42;
    }

    @Provides
    // BUG: Diagnostic contains: BindingToUnqualifiedCommonType
    Integer provideBoxedFoo() {
      return 42;
    }

    @Provides
    // BUG: Diagnostic contains: BindingToUnqualifiedCommonType
    String providesGreeting() {
      return "hi";
    }
  }
}

Negative examples

BindingToUnqualifiedCommonTypeNegativeCases.java

/*
 * Copyright 2016 Google Inc. 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.errorprone.bugpatterns.inject.guice.testdata;

import com.google.common.collect.ImmutableList;
import com.google.inject.AbstractModule;
import com.google.inject.Binder;
import com.google.inject.BindingAnnotation;
import com.google.inject.Module;
import com.google.inject.Provides;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.List;

/** Tests for {@code BindingToUnqualifiedCommonType} */
public class BindingToUnqualifiedCommonTypeNegativeCases {

  /** Regular module */
  class Module1 extends AbstractModule {
    @Override
    protected void configure() {
      // Bindings to unannotated complex instances
      bind(A.class).toInstance(new A());

      // Binding to literals, but with a binding annotation
      bind(Integer.class).annotatedWith(MyBindingAnnotation.class).toInstance(42);
    }

    @Provides
    List<Integer> providesFoo() {
      return ImmutableList.of(42);
    }
  }

  /** implements the Module interface directly */
  class Module2 implements Module {
    @Override
    public void configure(Binder binder) {}

    @Provides
    @MyBindingAnnotation
    int providesFoo() {
      return 42;
    }
  }

  class A {}

  @BindingAnnotation
  @Retention(RetentionPolicy.RUNTIME)
  @interface MyBindingAnnotation {}
}