ProtoFieldPreconditionsCheckNotNull
Protobuf fields cannot be null, so this check is redundant

Severity
WARNING
Tags
LikelyError
Has Fix?
REQUIRES_HUMAN_ATTENTION

The problem

This checker looks for comparisons of protocol buffer fields with null via the com.google.common.base.Preconditions.checkNotNull method. If a proto field is not specified, its field accessor will return a non-null default value. Thus, the result of calling one of these accessors can never be null, and comparisons like these often indicate a nearby error.

If you meant to check whether an optional field has been set, you should use the hasField() method instead.

Suppression

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


Positive examples

ProtoFieldPreconditionsCheckNotNullPositiveCases.java

/*
* Copyright 2014 The Error Prone 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 com.google.errorprone.bugpatterns.testdata;

import com.google.common.base.Preconditions;
import com.google.errorprone.bugpatterns.proto.ProtoTest.TestFieldProtoMessage;
import com.google.errorprone.bugpatterns.proto.ProtoTest.TestProtoMessage;

/**
* Positive examples for checking a proto message field using {@link
* Preconditions#checkNotNull(Object)} and related methods.
*/

public class ProtoFieldPreconditionsCheckNotNullPositiveCases {
public static void main(String[] args) {
TestProtoMessage message = TestProtoMessage.newBuilder().build();

// BUG: Diagnostic contains: check is redundant
// remove this line
Preconditions.checkNotNull(message.getMessage());
// BUG: Diagnostic contains: check is redundant
// remove this line
Preconditions.checkNotNull(message.getMultiFieldList());

// BUG: Diagnostic contains: check is redundant
// remove this line
Preconditions.checkNotNull(message.getMessage(), new Object());
// BUG: Diagnostic contains: check is redundant
// remove this line
Preconditions.checkNotNull(message.getMultiFieldList(), new Object());

// BUG: Diagnostic contains: check is redundant
// remove this line
Preconditions.checkNotNull(message.getMessage(), "%s", new Object());
// BUG: Diagnostic contains: check is redundant
// remove this line
Preconditions.checkNotNull(message.getMultiFieldList(), "%s", new Object());

// BUG: Diagnostic contains: fieldMessage = message.getMessage();
TestFieldProtoMessage fieldMessage = Preconditions.checkNotNull(message.getMessage());

// BUG: Diagnostic contains: fieldMessage2 = message.getMessage()
TestFieldProtoMessage fieldMessage2 = Preconditions.checkNotNull(message.getMessage(), "Msg");

// BUG: Diagnostic contains: message.getMessage().toString();
Preconditions.checkNotNull(message.getMessage()).toString();
// BUG: Diagnostic contains: message.getMessage().toString();
Preconditions.checkNotNull(message.getMessage(), "Message").toString();
}
}

Negative examples

ProtoFieldPreconditionsCheckNotNullNegativeCases.java

/*
* Copyright 2014 The Error Prone 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 com.google.errorprone.bugpatterns.testdata;

import com.google.errorprone.bugpatterns.proto.ProtoTest.TestProtoMessage;

/** Negative examples for invalid null comparison of a proto message field. */
public class ProtoFieldPreconditionsCheckNotNullNegativeCases {
public static void main(String[] args) {
TestProtoMessage message = TestProtoMessage.newBuilder().build();

// This is not {@link com.google.common.base.Preconditions#checkNotNull}, so it should
// be acceptable.
Preconditions.checkNotNull(message.getMessage());
Preconditions.checkNotNull(message.getMultiFieldList());
Preconditions.checkNotNull(message.getMessage(), "Message");
Preconditions.checkNotNull(message.getMultiFieldList(), "Message");
Preconditions.checkNotNull(message.getMessage(), "Message %s", new Object());
Preconditions.checkNotNull(message.getMultiFieldList(), "Message %s", new Object());

// Checking a non-proto object should be acceptable.
com.google.common.base.Preconditions.checkNotNull(new Object());
com.google.common.base.Preconditions.checkNotNull(new Object(), "Message");
com.google.common.base.Preconditions.checkNotNull(new Object(), "Message %s", new Object());
}

private static final class Preconditions {
private Preconditions() {}

static void checkNotNull(Object reference) {}

static void checkNotNull(Object reference, Object errorMessage) {}

static void checkNotNull(
Object reference, String errorMessageTemplate, Object... errorMessageArgs) {}
}
}