Create and install de-lomboked source jar in maven

The following solution is based on the one offered above but improves it by using the build-helper plugin to attach the generated delomboked source jar instead of using install-file. This has the benefit that the normal maven install and deploy phases correctly handle the generated file just as they would if the sources plugin had been used.

<project>
...
<build>
    <plugins>
        ...
        <plugin>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok-maven-plugin</artifactId>
            <version>1.18.12.0</version>
            <executions>
                <execution>
                    <id>delombok-sources</id>
                    <phase>generate-sources</phase>
                    <goals>
                        <goal>delombok</goal>
                    </goals>
                    <configuration>
                        <sourceDirectory>src/main/java</sourceDirectory>
                        <outputDirectory>${project.build.directory}/delombok</outputDirectory>
                        <addOutputDirectory>false</addOutputDirectory>
                        <encoding>UTF-8</encoding>
                    </configuration>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-antrun-plugin</artifactId>
            <version>1.8</version>
            <executions>
                <execution>
                    <id>generate-delomboked-sources-jar</id>
                    <phase>package</phase>
                    <goals>
                        <goal>run</goal>
                    </goals>
                    <configuration>
                        <target>
                            <jar destfile="${project.build.directory}/${project.build.finalName}-sources.jar"
                                 basedir="${project.build.directory}/delombok"/>
                        </target>
                    </configuration>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>build-helper-maven-plugin</artifactId>
            <version>3.1.0</version>
            <executions>
                <execution>
                    <id>attach-delomboked-sources-jar</id>
                    <phase>package</phase>
                    <goals>
                        <goal>attach-artifact</goal>
                    </goals>
                    <configuration>
                        <artifacts>
                            <artifact>
                                <file>${project.build.directory}/${project.build.finalName}-sources.jar</file>
                                <type>jar</type>
                                <classifier>sources</classifier>
                            </artifact>
                        </artifacts>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>
</project>

TL;DR (explained beneath)

Add the following plugins configuration to your plugins configuration in the project.build element of your pom.xml

<project>
    ...
<build>
<plugins>
    ...
<plugin>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok-maven-plugin</artifactId>
    <version>1.18.0.0</version>
    <executions>
        <execution>
            <phase>generate-sources</phase>
            <goals>
                <goal>delombok</goal>
            </goals>
        </execution>
    </executions>
    <configuration>
        <sourceDirectory>src/main/java</sourceDirectory>
        <outputDirectory>${project.build.directory}/delombok</outputDirectory>
        <addOutputDirectory>false</addOutputDirectory>
        <encoding>UTF-8</encoding>
    </configuration>
</plugin>
<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-resources-plugin</artifactId>
    <version>3.1.0</version>
    <executions>
        <execution>
            <id>copy-to-lombok-build</id>
            <phase>process-resources</phase>
            <goals>
                <goal>copy-resources</goal>
            </goals>
            <configuration>
                <resources>
                    <resource>
                        <directory>${project.basedir}/src/main/resources</directory>
                    </resource>
                </resources>
                <outputDirectory>${project.build.directory}/delombok</outputDirectory>
            </configuration>
        </execution>
    </executions>
</plugin>
<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-antrun-plugin</artifactId>
    <version>1.8</version>
    <executions>
        <execution>
            <id>generate-delomboked-sources-jar</id>
            <phase>package</phase>
            <goals>
                <goal>run</goal>
            </goals>
            <configuration>
                <target>
                    <jar destfile="${project.build.directory}/${project.build.finalName}-sources.jar"
                         basedir="${project.build.directory}/delombok"/>
                </target>
            </configuration>
        </execution>
    </executions>
</plugin>
<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-install-plugin</artifactId>
    <version>2.5.2</version>
    <executions>
        <execution>
            <id>install-source-jar</id>
            <goals>
                <goal>install-file</goal>
            </goals>
            <phase>install</phase>
            <configuration>
                <file>${project.build.directory}/${project.build.finalName}-sources.jar</file>
                <groupId>${project.groupId}</groupId>
                <artifactId>${project.artifactId}</artifactId>
                <version>${project.version}</version>
                <classifier>sources</classifier>
                <generatePom>true</generatePom>
                <pomFile>${project.basedir}/pom.xml</pomFile>
            </configuration>
        </execution>
    </executions>
</plugin>
</plugins>
</build>
</project>

Explanation

lombok-maven-plugin will enable you to delombok the source code (${project.basedir}/src/main/java) and place it in the target directory (${project.build.directory}/delombok). Usually this will place the code in the ${project.build.directory}/generated-sources/delombok folder, but because Intellij automatically considers this additional source-code, duplicate code errors will occur when developing your library, in order to stop this, just specify a non-default target directory (in this case just outside of the generated-sources dir).

maven-resources-plugin is necessary in order to also copy resources from the standard ${project.basedir}/src/main/resources directory. If there are any other non-standard resource directories in your project, you should configure them in the resources section for this plugin.

maven-antrun-plugin is used instead of the maven-source-plugin because you cannot specify a custom source directory in the later. The jar task points to our custom "generated-sources" and produces the standard-named sources jar.

maven-install-plugin install-file goal is used because you cannot attach jars using the install goal. We can hack a solution by manually installing a file using the install-file goal with a classifier of sources.

I hope this helps others who are on struggle street like I was with this problem.

Would like to point out that a profile can also be used (to get around the build source directory being un-customizable). The solution is described at https://sudonull.com/post/1197-Lombok-sourcesjar-and-convenient-debug

Add the following to the pom.xml properties:

<origSourceDir>${project.basedir}/src/main/java</origSourceDir>
<sourceDir>${origSourceDir}</sourceDir>
<delombokedSourceDir>${project.build.directory}/delombok</delombokedSourceDir>
</properties>

Profile and build section changes:

<profiles>
    <profile>
        <id>build</id>
        <properties>
            <sourceDir>${delombokedSourceDir}</sourceDir>
        </properties>
    </profile>
</profiles>
<build>
    <sourceDirectory>${sourceDir}</sourceDirectory>
    <plugins>
        <plugin>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok-maven-plugin</artifactId>
            <version>1.18.20.0</version>
            <executions>
                <execution>
                    <id>delombok</id>
                    <phase>generate-sources</phase>
                    <goals>
                        <goal>delombok</goal>
                    </goals>
                    <configuration>
                        <addOutputDirectory>false</addOutputDirectory>
                        <sourceDirectory>${origSourceDir}</sourceDirectory>
                        <outputDirectory>${delombokedSourceDir}</outputDirectory>
                    </configuration>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-source-plugin</artifactId>
            <version>3.0.1</version>
            <executions>
                <execution>
                    <id>attach-sources</id>
                    <goals>
                        <goal>jar</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>

Execute with mvn clean install -Pbuild

This should solve the "Library source does not match the bytecode for class" error in IntelliJ and allow seamless debugging in most cases.

Ref: "Delombok plugin + profile in maven"