Breaking change to plexus compiler api 2.9

The release of the plexus-compiler-api version 2.9 and release of the maven-compiler-plugin 2.5 has broken backwards compatibility. See GRECLIPSE-1441.

in 1.8.1:

CompilerConfiguration.getCustomCompilerArguments() returns LinkedHashMap

in 1.9:

CompilerConfiguration.getCustomCompilerArguments() returns  Map<String, String>

This means that a plugins compiled against one version will not work
against the other (java.lang.NoSuchMethodError is thrown). Is this
right? Am I missing something or must there be a strict dependency on
plexus-compiler-api (and hence the maven-compiler-plugin)?

I am attaching a failing maven project. When you run mvn clean compile on this project, it will fail with this error:

ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.5:compile (default-compile) on project org.codehaus.groovy: Execution default-compile of goal org.apache.maven.plugins:maven-compiler-plugin:2.5:compile failed: An API incompatibility was encountered while executing org.apache.maven.plugins:maven-compiler-plugin:2.5:compile: java.lang.NoSuchMethodError: org.codehaus.plexus.compiler.CompilerConfiguration.getCustomCompilerArguments()Ljava/util/LinkedHashMap;

If you edit the pom and change the maven-compile-plugin dependency to 2.3.2, the clean compile will succeed.

My suspicion is that if you change the signature of getCustomCompilerArguments to public LinkedHashMap<String, String> getCustomCompilerArguments(), this will succeed.