I'm not sure we want to change the maven 3 code base too much. I've tried to revert most changes to get back into a compatible state, so if we add a constructor, it might break something. And for not much value, as this code is not really used.

Agreed, the compat/maven-embedder changes should be undone.

@gnodet @cstamas I also agree with this and have reverted the compatibility logic of maven3.

There are two references to new DefaultInterpolator() that can be easily removed:

• maven/impl/maven-impl/src/main/java/org/apache/maven/internal/impl/DefaultSettingsBuilder.java

  Lines 83 to 85 in f5a407c

  	public DefaultSettingsBuilder() {
  	this(new DefaultSettingsXmlFactory(), new DefaultInterpolator(), Map.of());
  	}

• maven/impl/maven-impl/src/main/java/org/apache/maven/internal/impl/DefaultToolchainsBuilder.java

  Lines 60 to 62 in f5a407c

  	public DefaultToolchainsBuilder() {
  	this(new DefaultInterpolator(), new DefaultToolchainsXmlFactory());
  	}

We can simply inline those constructors, as they are only used in a few tests. This will move the references to the implementation to the tests instead of the main code.

There are two references to new DefaultInterpolator() that can be easily removed:

• maven/impl/maven-impl/src/main/java/org/apache/maven/internal/impl/DefaultSettingsBuilder.java

  Lines 83 to 85 in f5a407c

  	public DefaultSettingsBuilder() {
  	this(new DefaultSettingsXmlFactory(), new DefaultInterpolator(), Map.of());
  	}

• maven/impl/maven-impl/src/main/java/org/apache/maven/internal/impl/DefaultToolchainsBuilder.java

  Lines 60 to 62 in f5a407c

  	public DefaultToolchainsBuilder() {
  	this(new DefaultInterpolator(), new DefaultToolchainsXmlFactory());
  	}

We can simply inline those constructors, as they are only used in a few tests. This will move the references to the implementation to the tests instead of the main code.

@gnodet Done.

Resolve #9918