Question : NonOverridingEquals bug pattern

[euwnsep1225]

I expected NonOverridingEquals bug pattern and compiled the code, but the results were different than I expected. so I am sending this issue because I wonder if I have run the errorprone properly.

What version of Error Prone are you using?

2.3.1

Does this issue reproduce with the latest release?

N/A

What did you do?

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>Maven_2_Test</groupId>
  <artifactId>maven_sample</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>maven_sample</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.complier.source>1.6</maven.complier.source>
    <maven.complier.target>1.6</maven.complier.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
    <build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-compiler-plugin</artifactId>
      <version>3.3</version>
      <configuration>
        <compilerId>javac-with-errorprone</compilerId>
        <forceJavacCompilerUse>true</forceJavacCompilerUse>
        <!-- maven-compiler-plugin defaults to targeting Java 5, but our javac
             only supports >=6 -->
        <source>7</source>
        <target>7</target>
      </configuration>
      <dependencies>
        <dependency>
          <groupId>org.codehaus.plexus</groupId>
          <artifactId>plexus-compiler-javac-errorprone</artifactId>
          <version>2.8.3</version>
        </dependency>
        <!-- override plexus-compiler-javac-errorprone's dependency on
             Error Prone with the latest version -->
        <dependency>
          <groupId>com.google.errorprone</groupId>
          <artifactId>error_prone_core</artifactId>
          <version>2.3.1</version>
        </dependency>
      </dependencies>
    </plugin>
  </plugins>
</build>
</project>

Example.java

public class Example {
  private int value;

  public Example(int value) {
    this.value = value;
  }

  public boolean equals(Example other) {
    return this.value == other.value;
  }

  public static void main(String[] args) {
    Example exampleA = new Example(1);
    Example exampleB = new Example(1);
    System.out.println(exampleA.equals(exampleB));
  }
}

What did you expect to see?`

(see https://errorprone.info/bugpattern/NonOverridingEquals)

What did you see instead?

euwnsep@ubuntu:~/eclipse-workspace/maven_sample$ mvn compile
[INFO] Scanning for projects...
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building maven_sample 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ maven_sample ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /home/euwnsep/eclipse-workspace/maven_sample/src/main/resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.3:compile (default-compile) @ maven_sample ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to /home/euwnsep/eclipse-workspace/maven_sample/target/classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 6.816 s
[INFO] Finished at: 2018-06-06T08:33:04-07:00
[INFO] Final Memory: 20M/60M
[INFO] ------------------------------------------------------------------------

[cushon]

Note that we don't recommend plexus-compiler-javac-errorprone anymore, this is the recommended way to use Error Prone with maven: http://errorprone.info/docs/installation#maven

That example works for me using the maven instructions above, although I have to pass -Dmaven.compiler.showWarnings to get maven to actually display the warnings:

mvn clean package -Dmaven.compiler.showWarnings=true
...
[WARNING] ./Example.java:[8,18] [NonOverridingEquals] equals method doesn't override Object.equals
    (see https://errorprone.info/bugpattern/NonOverridingEquals)
  Did you mean '@Override'?