}

    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()));