How m2e detects what it automatically adds to .factorypath ?

[cvgaviao]

Hello. I'm facing a strange problem on Eclipse 202509 / 202512.

I have at least three processors on the project's classpath, as shown in the image below.

All three are properly defined as annotationProcessorPath in the maven-compiler-plugin

But m2e is adding only immutables to the .factorypath:

<factorypath>
    <factorypathentry kind="VARJAR" id="M2_REPO/org/immutables/value/2.11.3/value-2.11.3.jar" enabled="true" runInBatchMode="false"/>
</factorypath>

As a workaround, I added the missing two manually, but then they will disappear after a maven update.

[fbricon]

IIRC it detects annotation jars if they contain the proper metadata files. Usually mapstruct works. Can you share a sample project reproducing the issue?

[cvgaviao]

I believed I found the source of the problem.

I had a situation last week where Mapstruct processor was not being able to find some classes generated by Immutables, even if immutables processor was declared in the front of Mapstruct one in the maven-compiler.

After some hours of digging, I managed the problem by adding another compiler execution in the generate-source phase for immutables.

	<build>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<executions>
					<!-- Run immutables in generate-sources phase -->
					<execution>
						<id>generate-immutables</id>
						<phase>generate-sources</phase>
						<goals>
							<goal>compile</goal>
						</goals>
						<configuration>
							<proc>only</proc>
							<failOnError>false</failOnError>
							<annotationProcessorPaths>
								<annotationProcessorPath>
									<groupId>org.immutables</groupId>
									<artifactId>value</artifactId>
								</annotationProcessorPath>
							</annotationProcessorPaths>
							<generatedSourcesDirectory>
								${project.build.directory}/generated-sources/immutables</generatedSourcesDirectory>
							<verbose>${debug-processors}</verbose>
						</configuration>
					</execution>
					<!-- Added Hibernate and Mapstruct in the default compile, so Ide can get feedbacks -->
					<execution>
						<id>default-compile</id>
						<phase>compile</phase>
						<goals>
							<goal>compile</goal>
						</goals>
						<configuration>
							<verbose>${debug-processors}</verbose>
							<annotationProcessorPaths>
								<annotationProcessorPath>
									<groupId>org.mapstruct</groupId>
									<artifactId>mapstruct-processor</artifactId>
								</annotationProcessorPath>
								<annotationProcessorPath>
									<groupId>org.hibernate.orm</groupId>
									<artifactId>hibernate-processor</artifactId>
								</annotationProcessorPath>
							</annotationProcessorPaths>
						</configuration>
					</execution>
				</executions>
			</plugin>

            <!-- Add the Immutables generated sources to the compilation -->
			<plugin>
				<groupId>org.codehaus.mojo</groupId>
				<artifactId>build-helper-maven-plugin</artifactId>
				<executions>
					<execution>
						<id>add-immutables-sources</id>
						<phase>generate-sources</phase>
						<goals>
							<goal>add-source</goal>
						</goals>
						<configuration>
							<skipAddSourceIfMissing>true</skipAddSourceIfMissing>
							<sources>
								<source>target/generated-sources/immutables</source>
							</sources>
						</configuration>
					</execution>
				</executions>
			</plugin>

Since our CICD did not complain, I moved to another task, and only today I noted that Eclipse JDT was not working anymore.

M2e is using target/generated-sources/immutables as Generated source directory and the .factorypath contains only one jar.

Reverting the change to have all processors in the same executor made .factorypath to be produced properly:

					<execution>
						<id>default-compile</id>
						<phase>compile</phase>
						<goals>
							<goal>compile</goal>
						</goals>
						<configuration>
							<verbose>${debug-processors}</verbose>
							<annotationProcessorPaths>
								<annotationProcessorPath>
									<groupId>org.immutables</groupId>
									<artifactId>value</artifactId>
								</annotationProcessorPath>
								<annotationProcessorPath>
									<groupId>org.mapstruct</groupId>
									<artifactId>mapstruct-processor</artifactId>
								</annotationProcessorPath>
								<annotationProcessorPath>
									<groupId>org.hibernate.orm</groupId>
									<artifactId>hibernate-processor</artifactId>
								</annotationProcessorPath>
							</annotationProcessorPaths>
						</configuration>
					</execution>