Maven 4: MavenSession.lookup() NPE — PlexusContainer not injected for plugins using deprecated API #12986

Problem

Plugins that use the deprecated PlexusContainer injection via MavenSession.lookup() get a NullPointerException in Maven 4 because this.container is null:

[ERROR] Failed to execute goal org.codehaus.groovy.maven:gmaven-plugin:1.0:execute
  on project manual: java.lang.NullPointerException:
  Cannot invoke "org.codehaus.plexus.PlexusContainer.lookup(String)"
  because "this.container" is null

Stack trace:

at org.apache.maven.execution.MavenSession.lookup(MavenSession.java:477)
at org.codehaus.groovy.maven.plugin.execute.ExpressionEvaluatorImpl.lookupPathTranslator(...)
at org.codehaus.groovy.maven.plugin.execute.ExpressionEvaluatorImpl.<init>(...)

Affected project

• servicemix — uses gmaven-plugin:1.0 which calls MavenSession.lookup() internally

Analysis

MavenSession.container was deprecated but still used by several plugins. In Maven 4, it appears the field is no longer populated. While the API is deprecated, the result is a hard NPE rather than a graceful deprecation warning.

Expected behavior

Either:

1. Continue injecting the PlexusContainer into MavenSession for backward compatibility (with a deprecation warning)
2. Or throw a descriptive exception (e.g., UnsupportedOperationException("PlexusContainer injection was removed in Maven 4. Use JSR 330 injection instead.")) rather than an NPE

Context

Data from maven4-testing run #13307 testing maven-4.0.x against all Apache projects.