private List<Artifact> getTrail() throws OverConstrainedVersionException {
        if (trail == null) {
            List<Artifact> ids = new LinkedList<>();
            ResolutionNode node = this;
            while (node != null) {
                Artifact artifact = node.getArtifact();
                if (artifact.getVersion() == null) {
                    // set the recommended version

        if (reload) {
            if (reloadableFile == null) {
                throw new IllegalArgumentException("reloadableFile is null.");
            }
            return new InputStreamReader(new FileInputStream(reloadableFile), StandardCharsets.UTF_8);
        }

        Reader reader = null;
        if (settings.getAsList("synonyms", null) != null) {

     *
     * @param model The POM to extract the plugin configuration from, may be {@code null}.
     * @param pluginGroupId The group id of the plugin whose configuration should be used, must not be {@code null} or
     *            empty.
     * @param pluginArtifactId The artifact id of the plugin whose configuration should be used, must not be
     *            {@code null} or empty.

        if (path == null && url == null && reader == null && inputStream == null) {
            throw new IllegalArgumentException("path, url, reader or inputStream must be non null");
        }
        try {
            PluginDescriptorStaxReader xml = new PluginDescriptorStaxReader();
            xml.setAddDefaultEntities(request.isAddDefaultEntities());
            if (inputStream != null) {

     * created automatically.
     *
     * @param output The file to serialize the model to, must not be {@code null}.
     * @param options The options to use for serialization, may be {@code null} to use the default values.
     * @param model The model to serialize, must not be {@code null}.
     * @throws IOException If the model could not be serialized.
     */

    protected void assertObjectNotNull(String variableName, Object value) {
        if (variableName == null) {
            String msg = "The value should not be null: variableName=null value=" + value;
            throw new IllegalArgumentException(msg);
        }
        if (value == null) {
            String msg = "The value should not be null: variableName=" + variableName;
            throw new IllegalArgumentException(msg);
        }

            }

            if (location == null) {
                location = tracker.getLocation(EMPTY);
            }
        }

        return location != null ? new org.apache.maven.model.InputLocation(location) : null;
    }

    private static boolean equals(String s1, String s2) {
        String c1 = s1 == null ? "" : s1.trim();
        String c2 = s2 == null ? "" : s2.trim();
        return c1.equals(c2);

        if (available != null) {
            addFieldToSource(sourceMap, "available", available);
        }
        if (boost != null) {
            addFieldToSource(sourceMap, "boost", boost);
        }
        if (configParameter != null) {
            addFieldToSource(sourceMap, "configParameter", configParameter);
        }
        if (createdBy != null) {

            throws IntrospectionException {
        if (value == null || key == null) {
            return null;
        }

        if (value instanceof Map) {
            return ((Map) value).get(key);
        }

        final String message = String.format(
                "The token '%s' at position '%d' refers to a java.util.Map, but the value "

            if (textObj == null) {
                continue;
            }
            final String text = textObj.toString();
            final String lang = document.get(langFieldName) == null ? null : document.get(langFieldName).toString();

            final List<AnalyzeToken> tokens = analyzeText(analyzer, field, text, lang);
            if (tokens == null) {
                continue;
            }