module a {
  yang-version 1.1;
  namespace "a";
  prefix a;

  grouping a-grp {
    action a-act {
      input {
        leaf a-action-input-leaf {
          type empty;
        }
      }
    }
  }
  container a-cont {
    uses a:a-grp;
  }
}

module b {
  yang-version 1.1;
  namespace "b";
  prefix b;

  import a {
    prefix a;
  }

  augment "/a:a-cont/a:a-act/a:input" {
   description
      "An augmentation of a action input of module a";
    leaf b-aug-leaf {
      type empty;
    }
  }
}

[ERROR] yang-to-sources: Unable to generate sources with org.opendaylight.mdsal.binding.maven.api.gen.plugin.CodeGeneratorImpl generator
java.lang.NullPointerException: Target type not yet generated: InputEffectiveStatementImpl{path=AbsoluteSchemaPath{path=[(a)a-cont, (a)a-act, (a)input]}}
    at org.opendaylight.mdsal.binding.generator.impl.AbstractTypeGenerator.augmentationToGenTypes (AbstractTypeGenerator.java:796)
    at org.opendaylight.mdsal.binding.generator.impl.AbstractTypeGenerator.allAugmentsToGenTypes (AbstractTypeGenerator.java:375)
    at java.util.ArrayList.forEach (ArrayList.java:1257)
    at org.opendaylight.mdsal.binding.generator.impl.AbstractTypeGenerator.<init> (AbstractTypeGenerator.java:203)
    at org.opendaylight.mdsal.binding.generator.impl.CodegenTypeGenerator.<init> (CodegenTypeGenerator.java:32)
    at org.opendaylight.mdsal.binding.generator.impl.BindingGeneratorImpl.generateTypes (BindingGeneratorImpl.java:64)
    at org.opendaylight.mdsal.binding.maven.api.gen.plugin.CodeGeneratorImpl.generateSources (CodeGeneratorImpl.java:70)
    at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.generateSourcesWithOneGenerator (YangToSourcesProcessor.java:383)
    at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.generateSources (YangToSourcesProcessor.java:332)
    at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.conditionalExecute (YangToSourcesProcessor.java:159)
    at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesMojo.execute (YangToSourcesMojo.java:127)