}

    private InnerInterpolator createInterpolator( List<? extends ValueSource> valueSources,
                                                  List<? extends InterpolationPostProcessor> postProcessors,
                                                  final ModelProblemCollector problems )
    {
        final Map<String, String> cache = new HashMap<>();
        final StringSearchInterpolator interpolator = new StringSearchInterpolator();
        interpolator.setCacheAnswers( true );
        for ( ValueSource vs : valueSources )
        {
            interpolator.addValueSource( vs );
        }
        for ( InterpolationPostProcessor postProcessor : postProcessors )
        {
            interpolator.addPostProcessor( postProcessor );
        }
        final RecursionInterceptor recursionInterceptor = createRecursionInterceptor();
        return new InnerInterpolator()
        {
            @Override
            public String interpolate( String value )
            {
                if ( value != null && value.contains( "${" ) )
                {
                    String c = cache.get( value );
                    if ( c == null )
                    {
                        try
                        {
                            c = interpolator.interpolate( value, recursionInterceptor );
                        }
                        catch ( InterpolationException e )
                        {
                            problems.add( new ModelProblemCollectorRequest( Severity.ERROR, Version.BASE )
                                    .setMessage( e.getMessage() ).setException( e ) );
                        }
                        cache.put( value, c );
                    }
                    return c;
                }
                return value;
            }
        };
    }

                        master.put( key, element );

                        if ( !pending.isEmpty() )
                        {
                            predecessors.put( key, pending );
                            pending = new ArrayList<>();
                        }
                    }
                    else
                    {
                        pending.add( element );
                    }
                }

                List<Plugin> result = new ArrayList<>( src.size() + tgt.size() );
                for ( Map.Entry<Object, Plugin> entry : master.entrySet() )
                {
                    List<Plugin> pre = predecessors.get( entry.getKey() );
                    if ( pre != null )
                    {
                        result.addAll( pre );
                    }
                    result.add( entry.getValue() );
                }
                result.addAll( pending );

                target.setPlugins( result );
            }
        }

        @Override
        protected void mergePlugin( Plugin target, Plugin source, boolean sourceDominant, Map<Object, Object> context )

        private void visit( Plugin plugin )
        {
            if ( plugin != null )
            {
                String org, val;
                // Inherited
                org = plugin.getInherited();
                val = interpolate( org );
                if ( org != val )
                {
                    plugin.setInherited( val );
                }
                // Configuration
                visit( (Xpp3Dom) plugin.getConfiguration() );
                // GroupId
                org = plugin.getGroupId();
                val = interpolate( org );
                if ( org != val )
                {
                    plugin.setGroupId( val );
                }
                // ArtifactId
                org = plugin.getArtifactId();
                val = interpolate( org );
                if ( org != val )
                {
                    plugin.setArtifactId( val );
                }
                // Version
                org = plugin.getVersion();
                val = interpolate( org );
                if ( org != val )
                {
                    plugin.setVersion( val );
                }

            List<Repository> tgt = target.getRepositories();
            Map<Object, Repository> merged = new LinkedHashMap<>( ( src.size() + tgt.size() ) * 2 );

            List<Repository> dominant, recessive;
            if ( sourceDominant )
            {
                dominant = src;
                recessive = tgt;
            }
            else
            {
                dominant = tgt;
                recessive = src;
            }

            for ( Repository element : dominant )
            {
                Object key = getRepositoryKey( element );
                merged.put( key, element );
            }

            for ( Repository element : recessive )
            {
                Object key = getRepositoryKey( element );
                if ( !merged.containsKey( key ) )
                {
                    merged.put( key, element );
                }
            }

            target.setRepositories( new ArrayList<>( merged.values() ) );