Plexus and Maven

Prior to Maven 3.9, a component named plexus-tools was included by Apache Maven at runtime. The component is used by Maven plugin internals. In v3.9.0 of Maven, this was removed. Some older Maven plugins may still need this dependency to work. The protobuf-maven-plugin does not require this to operate in normal cases.

Under some conditions, it appears that the use of certain other plugins or extensions triggers an issue within Maven where plexus-utils becomes a requirement. A current known case occurs when users make use of the Maven Cache Extension. The following error may be observed if this issue is encountered:

[ERROR] org.apache.maven.plugin.PluginContainerException: Unable to load the mojo 'generate' (or one of its required components) from the plugin 'io.github.ascopes:protobuf-maven-plugin:2.7.0': com.google.inject.ProvisionException: Unable to provision, see the following errors:
[ERROR] 
[ERROR] 1) [Guice/ErrorInCustomProvider]: IllegalStateException
[ERROR]   at MojoExecutionScopeModule.configure(MojoExecutionScopeModule.java:50)
[ERROR]       \_ installed by: WireModule -> MojoExecutionScopeModule
[ERROR]   at TemporarySpace.<init>(TemporarySpace.java:45)
[ERROR]       \_ for 2nd parameter
[ERROR]   at UrlResourceFetcher.<init>(UrlResourceFetcher.java:65)
[ERROR]       \_ for 1st parameter
[ERROR]   at ProtocResolver.<init>(ProtocResolver.java:63)
[ERROR]       \_ for 5th parameter
[ERROR]   at ProtobufBuildOrchestrator.<init>(ProtobufBuildOrchestrator.java:71)
[ERROR]       \_ for 2nd parameter
[ERROR]   at AbstractGenerateMojo.sourceCodeGenerator(AbstractGenerateMojo.java:71)
[ERROR]       \_ for field sourceCodeGenerator
[ERROR]   while locating MainGenerateMojo
[ERROR]   at ClassRealm[plugin>io.github.ascopes:protobuf-maven-plugin:2.7.0, parent: ClassLoaders$AppClassLoader@531d72ca]
[ERROR]       \_ installed by: WireModule -> PlexusBindingModule
[ERROR]   while locating Mojo annotated with @Named("io.github.ascopes:protobuf-maven-plugin:2.7.0:generate")

Note that other errors like this may also occur.

The workaround for now appears to be to include plexus-utils explicitly as a dependency of this plugin:

<plugin>
  <groupId>io.github.ascopes</groupId>
  <artifactId>protobuf-maven-plugin</artifactId>
  <version>...</version>

  <configuration>...</configuration>
  <executions>...</executions>

  <dependencies>
    <dependency>
      <groupId>org.codehaus.plexus</groupId>
      <artifactId>plexus-utils</artifactId>
      <version>4.0.2</version>
    </dependency>
  </dependencies>
</plugin>

See GH-472 for tracking this issue.

Heap exhaustion under some configurations

GH-596 tracks an issue some users have raised when utilising large numbers of dependencies in their projects. The issue results in Eclipse Aether APIs exhausting heap memory, but so far appears to only occur if invoking Maven via IntelliJ IDEA.

We suspect this is an issue with Eclipse Aether itself, which is provided by Maven to allow plugins to perform custom dependency resolution.

The v2.13.0 release of this Maven plugin has moved most of the dependency resolution over to Maven to perform prior to invoking the plugin, but we still do not have a working reproduction of this issue at the time of writing. If you are able to provide a minimal working reproduction, please submit it at the link above.