jacoco : Cannot exclude classes

Question

I have a maven project and I want to use jacoco for code coverage. Here is the relevant section of my pom

          <plugin>
                <groupId>org.jacoco</groupId>
                <artifactId>jacoco-maven-plugin</artifactId>
                <version>0.7.5.201505241946</version>
                <executions>
                    <execution>
                        <id>pre-my-test</id>
                        <phase>pre-integration-test</phase>
                        <goals>
                            <goal>prepare-agent</goal>
                        </goals>
                        <configuration>
                            <append>true</append>
                            <destFile>${project.build.directory}/jacoco-it.exec</destFile>
                            <propertyName>failsafeArgLine</propertyName>
                        </configuration>
                    </execution>
                    <execution>
                        <id>post-my-test</id>
                        <phase>post-my-test</phase>
                        <goals>
                            <goal>report</goal>
                        </goals>
                        <configuration>
                            <dataFile>${project.build.directory}/jacoco-it.exec</dataFile>
                            <outputDirectory>${project.reporting.outputDirectory}/jacoco-it</outputDirectory>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

So I am able to run my tests just fine and also build the project just fine. Then I run

mvn clean verify org.jacoco:jacoco-maven-plugin:prepare-agent

I keep getting errors like

ERROR] Failed to execute goal org.jacoco:jacoco-maven-plugin:0.7.5.201505241946:
report (post-my-test) on project my-project: 
An error has occurred in JaCoCo Test report generation. 
Error while creating report: 
Error while analyzing class /path/tp/my/project/target/classes/META-INF/
bundled-dependencies/some-third-party-1-jar-with-dependencies.jar@org/slf4j/event/
EventConstants.class. Can't add different class with same name: 
org/slf4j/event/EventConstants -> [Help 1]

some-third-party-1-jar-with-dependencies.jar is an external dependency that I have. This is an uber/shaded jar. So I thought that some-third-party-1-jar-with-dependencies.jar must also have org.slf4j, hence the conflict. So I made a change to the pom as

            <plugin>
                <groupId>org.jacoco</groupId>
                <artifactId>jacoco-maven-plugin</artifactId>
                <version>0.7.5.201505241946</version>
                <configuration>
                    <excludes>
                        <exclude>**/org/slf4j/event/EventConstants.*</exclude>
                    </excludes>
                </configuration>
                <executions>
                    <execution>
                        <id>pre-integration-test</id>
                        <phase>pre-integration-test</phase>
                        <goals>
                            <goal>prepare-agent</goal>
                        </goals>
                        <configuration>
                            <append>true</append>
                            <destFile>${project.build.directory}/jacoco-it.exec</destFile>
                            <propertyName>failsafeArgLine</propertyName>
                        </configuration>
                    </execution>
                    <execution>
                        <id>post-integration-test</id>
                        <phase>post-integration-test</phase>
                        <goals>
                            <goal>report</goal>
                        </goals>
                        <configuration>
                            <dataFile>${project.build.directory}/jacoco-it.exec</dataFile>
                            <outputDirectory>${project.reporting.outputDirectory}/jacoco-it</outputDirectory>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

but I still get the same error. How can I make sure that jacoco ignores all duplicate dependencies? I also tried

<dependency>
            <groupId>some.third.party</groupId>
            <artifactId>some-third-party</artifactId>
            <version>1</version>
            <classifier>jar-with-dependencies</classifier>
            <exclusions>
                <exclusion>
                    <groupId>org.slf4j</groupId>
                    <artifactId>slf4j-api</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>org.slf4j</groupId>
                    <artifactId>slf4j-log4j12</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>org.slf4j</groupId>
                    <artifactId>slf4j-simple</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

but that did not work. Is it possible to have exclusions from shaded/uber jars?

Moreover, why does jacoco care? Is there any way to fix or ignore these errors? How can I resolve this issue?

Answer 1

Property excludes of report goal specifies which files should be excluded from analysis during generation of report. In case of /path/tp/my/project/target/classes/META-INF/bundled-dependencies/some-third-party-1-jar-with-dependencies.jar@org/slf4j/event/EventConstants.class file is /path/tp/my/project/target/classes/META-INF/bundled-dependencies/some-third-party-1-jar-with-dependencies.jar , and the rest is about class in JAR file.

Therefore as one of examples of correct configuration:

<configuration>
  <excludes>
    <exclude>META-INF/**</exclude>
  </excludes>
</configuration>

As a proof having pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>org.example</groupId>
  <artifactId>example</artifactId>
  <version>1.0-SNAPSHOT</version>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.jacoco</groupId>
        <artifactId>jacoco-maven-plugin</artifactId>
        <version>0.8.1</version>
      </plugin>
    </plugins>
  </build>

</project>

src/main/java/Example.java

public class Example {
}

and src/test/java/ExampleTest.java

public class ExampleTest {
  @org.junit.Test
  public void test() {
  }
}

Execution of

mvn clean jacoco:prepare-agent package
mkdir target/classes/META-INF/
cp ~/.m2/repository/org/slf4j/slf4j-api/1.4.2/slf4j-api-1.4.2.jar target/classes
cp ~/.m2/repository/org/slf4j/slf4j-api/1.7.7/slf4j-api-1.7.7.jar target/classes/META-INF
mvn jacoco:report

will fail with message

Error while analyzing /private/tmp/j/target/classes/slf4j-api-1.4.2.jar@org/slf4j/helpers/BasicMarker.class. Can't add different class with same name: org/slf4j/helpers/BasicMarker

while same execution with pom.xml containing exclusion of META-INF/**

<?xml version="1.0" encoding="UTF-8"?>
<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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>org.example</groupId>
  <artifactId>example</artifactId>
  <version>1.0-SNAPSHOT</version>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.jacoco</groupId>
        <artifactId>jacoco-maven-plugin</artifactId>
        <version>0.8.1</version>
        <configuration>
          <excludes>
            <exclude>META-INF/**</exclude>
          </excludes>
        </configuration>
      </plugin>
    </plugins>
  </build>

</project>

will succeed.

As a side note: semantic of property excludes of prepare-agent goal is different - it specifies class names (regardless of their on-disk location) that should be excluded from instrumentation during execution of tests.