class FormState

class FormState implements FormStateInterface {
    use FormStateValuesTrait;
    
    /**
     * Tracks if any errors have been set on any form.
     *
     * @var bool
     */
    protected static $anyErrors = FALSE;
    
    /**
     * The complete form structure.
     *
     * #process, #after_build, #element_validate, and other handlers being invoked
     * on a form element may use this reference to access other information in the
     * form the element is contained in.
     *
     * @see self::getCompleteForm()
     *
     * This property is uncacheable.
     *
     * @var array
     */
    protected $complete_form;
    
    /**
     * An associative array of information stored by Form API.
     *
     * This associative array is necessary to build and rebuild the form from
     * cache when the original context may no longer be available:
     *   - callback: The actual callback to be used to retrieve the form array.
     *     Can be any callable. If none is provided $form_id is used as the name
     *     of a function to call instead.
     *   - args: A list of arguments to pass to the form constructor.
     *   - files: An optional array defining include files that need to be loaded
     *     for building the form. Each array entry may be the path to a file or
     *     another array containing values for the parameters 'type', 'module' and
     *     'name' as needed by \Drupal::moduleHandler()->loadInclude(). The files
     *     listed here are automatically loaded by
     *     \Drupal::formBuilder()->getCache(). By default the current menu router
     *     item's 'file' definition is added, if any. Use self::loadInclude() to
     *     add include files from a form constructor.
     *   - form_id: Identification of the primary form being constructed and
     *     processed.
     *   - base_form_id: Identification for a base form, as declared in the form
     *     class's \Drupal\Core\Form\BaseFormIdInterface::getBaseFormId() method.
     *   - immutable: If this flag is set to TRUE, a new form build id is
     *     generated when the form is loaded from the cache. If it is subsequently
     *     saved to the cache again, it will have another cache id and therefore
     *     the original form and form-state will remain unaltered. This is
     *     important when page caching is enabled in order to prevent form state
     *     from leaking between anonymous users.
     *
     * @var array
     */
    protected $build_info = [
        'args' => [],
        'files' => [],
    ];
    
    /**
     * Similar to self::$build_info.
     *
     * But pertaining to \Drupal\Core\Form\FormBuilderInterface::rebuildForm().
     *
     * This property is uncacheable.
     *
     * @var array
     */
    protected $rebuild_info = [];
    
    /**
     * Determines whether the form is rebuilt.
     *
     * Normally, after the entire form processing is completed and submit handlers
     * have run, a form is considered to be done and
     * \Drupal\Core\Form\FormSubmitterInterface::redirectForm() will redirect the
     * user to a new page using a GET request (so a browser refresh does not
     * re-submit the form). However, if 'rebuild' has been set to TRUE, then a new
     * copy of the form is immediately built and sent to the browser, instead of a
     * redirect. This is used for multi-step forms, such as wizards and
     * confirmation forms. Normally, self::$rebuild is set by a submit handler,
     * since it is usually logic within a submit handler that determines whether a
     * form is done or requires another step. However, a validation handler may
     * already set self::$rebuild to cause the form processing to bypass submit
     * handlers and rebuild the form instead, even if there are no validation
     * errors.
     *
     * This property is uncacheable.
     *
     * @see self::setRebuild()
     *
     * @var bool
     */
    protected $rebuild = FALSE;
    
    /**
     * Determines if only safe element value callbacks are called.
     *
     * If set to TRUE the form will skip calling form element value callbacks,
     * except for a select list of callbacks provided by Drupal core that are
     * known to be safe.
     *
     * This property is uncacheable.
     *
     * @see self::setInvalidToken()
     *
     * @var bool
     */
    protected $invalidToken = FALSE;
    
    /**
     * The response object.
     *
     * Used when a form needs to return some kind of a
     * \Symfony\Component\HttpFoundation\Response object, e.g., a
     * \Symfony\Component\HttpFoundation\BinaryFileResponse when triggering a
     * file download. If you use self::setRedirect() or self::setRedirectUrl(),
     * it will be used to build a
     * \Symfony\Component\HttpFoundation\RedirectResponse and will populate this
     * key.
     *
     * @var \Symfony\Component\HttpFoundation\Response|null
     */
    protected $response;
    
    /**
     * Used to redirect the form on submission.
     *
     * @see self::getRedirect()
     *
     * This property is uncacheable.
     *
     * @var \Drupal\Core\Url|\Symfony\Component\HttpFoundation\RedirectResponse|null
     */
    protected $redirect;
    
    /**
     * If set to TRUE the form will NOT perform a redirect.
     *
     * Redirect will not be performed, even if self::$redirect is set.
     *
     * This property is uncacheable.
     *
     * @var bool
     */
    protected $no_redirect;
    
    /**
     * The HTTP form method to use for finding the input for this form.
     *
     * May be 'POST' or 'GET'. Defaults to 'POST'. Note that 'GET' method forms do
     * not use form ids so are always considered to be submitted, which can have
     * unexpected effects. The 'GET' method should only be used on forms that do
     * not change data, as that is exclusively the domain of 'POST.'
     *
     * This property is uncacheable.
     *
     * @var string
     */
    protected $method = 'POST';
    
    /**
     * The HTTP method used by the request building or processing this form.
     *
     * May be any valid HTTP method. Defaults to 'GET', because even though
     * $method is 'POST' for most forms, the form's initial build is usually
     * performed as part of a GET request.
     *
     * This property is uncacheable.
     *
     * @var string
     */
    protected $requestMethod = 'GET';
    
    /**
     * Determines if the unprocessed form structure is cached.
     *
     * If set to TRUE the original, unprocessed form structure will be cached,
     * which allows the entire form to be rebuilt from cache. A typical form
     * workflow involves two page requests; first, a form is built and rendered
     * for the user to fill in. Then, the user fills the form in and submits it,
     * triggering a second page request in which the form must be built and
     * processed. By default, $form and $form_state are built from scratch during
     * each of these page requests. Often, it is necessary or desired to persist
     * the $form and $form_state variables from the initial page request to the
     * one that processes the submission. 'cache' can be set to TRUE to do this.
     * A prominent example is an Ajax-enabled form, in which
     * \Drupal\Core\Render\Element\RenderElement::processAjaxForm()
     * enables form caching for all forms that include an element with the #ajax
     * property. (The Ajax handler has no way to build the form itself, so must
     * rely on the cached version.) Note that the persistence of $form and
     * $form_state happens automatically for (multi-step) forms having the
     * self::$rebuild flag set, regardless of the value for self::$cache.
     *
     * @var bool
     */
    protected $cache = FALSE;
    
    /**
     * If set to TRUE the form will NOT be cached, even if 'cache' is set.
     *
     * @var bool
     */
    protected $no_cache;
    
    /**
     * An associative array of values submitted to the form.
     *
     * The validation functions and submit functions use this array for nearly all
     * their decision making. (Note that #tree determines whether the values are a
     * flat array or an array whose structure parallels the $form array. See
     * \Drupal\Core\Render\Element\FormElement for more information.)
     *
     * This property is uncacheable.
     *
     * @var array
     */
    protected $values = [];
    
    /**
     * An associative array of form value keys to be removed by cleanValues().
     *
     * Any values that are temporary but must still be displayed as values in
     * the rendered form should be added to this array using addCleanValueKey().
     * Initialized with internal Form API values.
     *
     * This property is uncacheable.
     *
     * @var array
     */
    protected $cleanValueKeys = [
        'form_id',
        'form_token',
        'form_build_id',
        'op',
    ];
    
    /**
     * The array of values as they were submitted by the user.
     *
     * These are raw and unvalidated, so should not be used without a thorough
     * understanding of security implications. In almost all cases, code should
     * use the data in the 'values' array exclusively. The most common use of this
     * key is for multi-step forms that need to clear some of the user input when
     * setting 'rebuild'. The values correspond to \Drupal::request()->request or
     * \Drupal::request()->query, depending on the 'method' chosen.
     *
     * This property is uncacheable.
     *
     * @var array|null
     *   The submitted user input array, or NULL if no input was submitted yet.
     */
    protected $input;
    
    /**
     * If TRUE and the method is GET, a form_id is not necessary.
     *
     * This property is uncacheable.
     *
     * @var bool
     */
    protected $always_process;
    
    /**
     * Indicates if a validation will be forced.
     *
     * Ordinarily, a form is only validated once, but there are times when a form
     * is resubmitted internally and should be validated again. Setting this to
     * TRUE will force that to happen. This is most likely to occur during Ajax
     * operations.
     *
     * This property is uncacheable.
     *
     * @var bool
     */
    protected $must_validate;
    
    /**
     * Indicates if the form was submitted programmatically.
     *
     * If TRUE, the form was submitted programmatically, usually invoked via
     * \Drupal\Core\Form\FormBuilderInterface::submitForm(). Defaults to FALSE.
     *
     * @var bool
     */
    protected $programmed = FALSE;
    
    /**
     * Indicates if programmatic form submissions bypasses #access check.
     *
     * If TRUE, programmatic form submissions are processed without taking #access
     * into account. Set this to FALSE when submitting a form programmatically
     * with values that may have been input by the user executing the current
     * request; this will cause #access to be respected as it would on a normal
     * form submission. Defaults to TRUE.
     *
     * @var bool
     */
    protected $programmed_bypass_access_check = TRUE;
    
    /**
     * Indicates correct form submission.
     *
     * TRUE signifies correct form submission. This is always TRUE for programmed
     * forms coming from \Drupal\Core\Form\FormBuilderInterface::submitForm() (see
     * 'programmed' key), or if the form_id coming from the
     * \Drupal::request()->request data is set and matches the current form_id.
     *
     * @var bool
     */
    protected $process_input;
    
    /**
     * If TRUE, the form has been submitted. Defaults to FALSE.
     *
     * This property is uncacheable.
     *
     * @var bool
     */
    protected $submitted = FALSE;
    
    /**
     * If TRUE, the form was submitted and has been processed and executed.
     *
     * This property is uncacheable.
     *
     * @var bool
     */
    protected $executed = FALSE;
    
    /**
     * The form element that triggered submission.
     *
     * This may or may not be a button (in the case of Ajax forms). This key is
     * often used to distinguish between various buttons in a submit handler, and
     * is also used in Ajax handlers.
     *
     * This property is uncacheable.
     *
     * @var array|null
     */
    protected $triggering_element;
    
    /**
     * Indicates a file element is present.
     *
     * If TRUE, there is a file element and Form API will set the appropriate
     * 'enctype' HTML attribute on the form.
     *
     * @var bool
     */
    protected $has_file_element;
    
    /**
     * Contains references to details elements to render them within vertical tabs.
     *
     * This property is uncacheable.
     *
     * @var array
     */
    protected $groups = [];
    
    /**
     * The storage.
     *
     * This is not a special key, and no specific support is provided for it in
     * the Form API. By tradition it was the location where application-specific
     * data was stored for communication between the submit, validation, and form
     * builder functions, especially in a multi-step-style form. Form
     * implementations may use any key(s) within $form_state (other than the keys
     * listed here and other reserved ones used by Form API internals) for this
     * kind of storage. The recommended way to ensure that the chosen key doesn't
     * conflict with ones used by the Form API or other modules is to use the
     * module name as the key name or a prefix for the key name. For example, the
     * entity form classes use $this->entity in entity forms, or
     * $form_state->getFormObject()->getEntity() outside the controller, to store
     * information about the entity being edited, and this information stays
     * available across successive clicks of the "Preview" button (if available)
     * as well as when the "Save" button is finally clicked.
     *
     * @var array
     */
    protected $storage = [];
    
    /**
     * A list containing copies of all submit and button elements in the form.
     *
     * This property is uncacheable.
     *
     * @var array
     */
    protected $buttons = [];
    
    /**
     * Holds temporary data accessible during the current page request only.
     *
     * All $form_state properties that are not reserved keys (see
     * other properties marked as uncacheable) persist throughout a multistep form
     * sequence. Form API provides this key for modules to communicate information
     * across form-related functions during a single page request. It may be used
     * to temporarily save data that does not need to or should not be cached
     * during the whole form workflow; e.g., data that needs to be accessed during
     * the current form build process only. There is no use-case for this
     * functionality in Drupal core.
     *
     * This property is uncacheable.
     *
     * @var array
     */
    protected $temporary = [];
    
    /**
     * Tracks if the form has finished validation.
     *
     * This property is uncacheable.
     *
     * @var bool
     */
    protected $validation_complete = FALSE;
    
    /**
     * Contains errors for this form.
     *
     * This property is uncacheable.
     *
     * @var array
     */
    protected $errors = [];
    
    /**
     * Stores which errors should be limited during validation.
     *
     * An array of "sections" within which user input must be valid. If the
     * element is within one of these sections, the error must be recorded.
     * Otherwise, it can be suppressed. self::$limit_validation_errors can be an
     * empty array, in which case all errors are suppressed. For example, a
     * "Previous" button might want its submit action to be triggered even if none
     * of the submitted values are valid.
     *
     * This property is uncacheable.
     *
     * @var array|null
     */
    protected $limit_validation_errors;
    
    /**
     * Stores the gathered validation handlers.
     *
     * This property is uncacheable.
     *
     * @var array
     */
    protected $validate_handlers = [];
    
    /**
     * Stores the gathered submission handlers.
     *
     * This property is uncacheable.
     *
     * @var array
     */
    protected $submit_handlers = [];
    
    /**
     * {@inheritdoc}
     */
    public function setFormState(array $form_state_additions) {
        foreach ($form_state_additions as $key => $value) {
            if (property_exists($this, $key)) {
                $this->{$key} = $value;
            }
            else {
                $this->set($key, $value);
            }
        }
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setAlwaysProcess($always_process = TRUE) {
        $this->always_process = (bool) $always_process;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getAlwaysProcess() {
        return $this->always_process;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setButtons(array $buttons) {
        $this->buttons = $buttons;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getButtons() {
        return $this->buttons;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setCached($cache = TRUE) {
        // Persisting $form_state is a side-effect disallowed during a "safe" HTTP
        // method.
        if ($cache && $this->isRequestMethodSafe()) {
            throw new \LogicException(sprintf('Form state caching on %s requests is not allowed.', $this->requestMethod));
        }
        $this->cache = (bool) $cache;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isCached() {
        return empty($this->no_cache) && $this->cache;
    }
    
    /**
     * {@inheritdoc}
     */
    public function disableCache() {
        $this->no_cache = TRUE;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setExecuted() {
        $this->executed = TRUE;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isExecuted() {
        return $this->executed;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setGroups(array $groups) {
        $this->groups = $groups;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function &getGroups() {
        return $this->groups;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setHasFileElement($has_file_element = TRUE) {
        $this->has_file_element = (bool) $has_file_element;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasFileElement() {
        return $this->has_file_element;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setLimitValidationErrors($limit_validation_errors) {
        $this->limit_validation_errors = $limit_validation_errors;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getLimitValidationErrors() {
        return $this->limit_validation_errors;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setMethod($method) {
        $this->method = strtoupper($method);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isMethodType($method_type) {
        return $this->method === strtoupper($method_type);
    }
    
    /**
     * {@inheritdoc}
     */
    public function setRequestMethod($method) {
        $this->requestMethod = strtoupper($method);
        return $this;
    }
    
    /**
     * Checks whether the request method is a "safe" HTTP method.
     *
     * Link below defines GET and HEAD as "safe" methods, meaning they SHOULD NOT
     * have side-effects, such as persisting $form_state changes.
     *
     * @return bool
     *
     * @see \Symfony\Component\HttpFoundation\Request::isMethodSafe()
     * @see http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.1.1
     */
    protected function isRequestMethodSafe() {
        return in_array($this->requestMethod, [
            'GET',
            'HEAD',
        ]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function setValidationEnforced($must_validate = TRUE) {
        $this->must_validate = (bool) $must_validate;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isValidationEnforced() {
        return $this->must_validate;
    }
    
    /**
     * {@inheritdoc}
     */
    public function disableRedirect($no_redirect = TRUE) {
        $this->no_redirect = (bool) $no_redirect;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isRedirectDisabled() {
        return $this->no_redirect;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setProcessInput($process_input = TRUE) {
        $this->process_input = (bool) $process_input;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isProcessingInput() {
        return $this->process_input;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setProgrammed($programmed = TRUE) {
        $this->programmed = (bool) $programmed;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isProgrammed() {
        return $this->programmed;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setProgrammedBypassAccessCheck($programmed_bypass_access_check = TRUE) {
        $this->programmed_bypass_access_check = (bool) $programmed_bypass_access_check;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isBypassingProgrammedAccessChecks() {
        return $this->programmed_bypass_access_check;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setRebuildInfo(array $rebuild_info) {
        $this->rebuild_info = $rebuild_info;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getRebuildInfo() {
        return $this->rebuild_info;
    }
    
    /**
     * {@inheritdoc}
     */
    public function addRebuildInfo($property, $value) {
        $rebuild_info = $this->getRebuildInfo();
        $rebuild_info[$property] = $value;
        $this->setRebuildInfo($rebuild_info);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setStorage(array $storage) {
        $this->storage = $storage;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function &getStorage() {
        return $this->storage;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setSubmitHandlers(array $submit_handlers) {
        $this->submit_handlers = $submit_handlers;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getSubmitHandlers() {
        return $this->submit_handlers;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setSubmitted() {
        $this->submitted = TRUE;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isSubmitted() {
        return $this->submitted;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setTemporary(array $temporary) {
        $this->temporary = $temporary;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getTemporary() {
        return $this->temporary;
    }
    
    /**
     * {@inheritdoc}
     */
    public function &getTemporaryValue($key) {
        $value =& NestedArray::getValue($this->temporary, (array) $key);
        return $value;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setTemporaryValue($key, $value) {
        NestedArray::setValue($this->temporary, (array) $key, $value, TRUE);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasTemporaryValue($key) {
        $exists = NULL;
        NestedArray::getValue($this->temporary, (array) $key, $exists);
        return $exists;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setTriggeringElement($triggering_element) {
        $this->triggering_element = $triggering_element;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function &getTriggeringElement() {
        return $this->triggering_element;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setValidateHandlers(array $validate_handlers) {
        $this->validate_handlers = $validate_handlers;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getValidateHandlers() {
        return $this->validate_handlers;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setValidationComplete($validation_complete = TRUE) {
        $this->validation_complete = (bool) $validation_complete;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isValidationComplete() {
        return $this->validation_complete;
    }
    
    /**
     * {@inheritdoc}
     */
    public function loadInclude($module, $type, $name = NULL) {
        if (!isset($name)) {
            $name = $module;
        }
        $build_info = $this->getBuildInfo();
        if (!isset($build_info['files']["{$module}:{$name}.{$type}"])) {
            // Only add successfully included files to the form state.
            if ($result = $this->moduleLoadInclude($module, $type, $name)) {
                $build_info['files']["{$module}:{$name}.{$type}"] = [
                    'type' => $type,
                    'module' => $module,
                    'name' => $name,
                ];
                $this->setBuildInfo($build_info);
                return $result;
            }
        }
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCacheableArray() {
        return [
            'build_info' => $this->getBuildInfo(),
            'response' => $this->getResponse(),
            'programmed' => $this->isProgrammed(),
            'programmed_bypass_access_check' => $this->isBypassingProgrammedAccessChecks(),
            'process_input' => $this->isProcessingInput(),
            'has_file_element' => $this->hasFileElement(),
            'storage' => $this->getStorage(),
            // Use the properties directly, since self::isCached() combines them and
            // cannot be relied upon.
'cache' => $this->cache,
            'no_cache' => $this->no_cache,
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function setCompleteForm(array &$complete_form) {
        $this->complete_form =& $complete_form;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function &getCompleteForm() {
        return $this->complete_form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function &get($property) {
        $value =& NestedArray::getValue($this->storage, (array) $property);
        return $value;
    }
    
    /**
     * {@inheritdoc}
     */
    public function set($property, $value) {
        NestedArray::setValue($this->storage, (array) $property, $value, TRUE);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function has($property) {
        $exists = NULL;
        NestedArray::getValue($this->storage, (array) $property, $exists);
        return $exists;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setBuildInfo(array $build_info) {
        $this->build_info = $build_info;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getBuildInfo() {
        return $this->build_info;
    }
    
    /**
     * {@inheritdoc}
     */
    public function addBuildInfo($property, $value) {
        $build_info = $this->getBuildInfo();
        $build_info[$property] = $value;
        $this->setBuildInfo($build_info);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function &getUserInput() {
        return $this->input;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setUserInput(array $user_input) {
        $this->input = $user_input;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function &getValues() {
        return $this->values;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setResponse(Response $response) {
        $this->response = $response;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getResponse() {
        return $this->response;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setRedirect($route_name, array $route_parameters = [], array $options = []) {
        $url = new Url($route_name, $route_parameters, $options);
        return $this->setRedirectUrl($url);
    }
    
    /**
     * {@inheritdoc}
     */
    public function setRedirectUrl(Url $url) {
        $this->redirect = $url;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getRedirect() {
        // Skip redirection for form submissions invoked via
        // \Drupal\Core\Form\FormBuilderInterface::submitForm().
        if ($this->isProgrammed()) {
            return FALSE;
        }
        // Skip redirection if rebuild is activated.
        if ($this->isRebuilding()) {
            return FALSE;
        }
        // Skip redirection if it was explicitly disallowed.
        if ($this->isRedirectDisabled()) {
            return FALSE;
        }
        return $this->redirect;
    }
    
    /**
     * Sets the global status of errors.
     *
     * @param bool $errors
     *   TRUE if any form has any errors, FALSE otherwise.
     */
    protected static function setAnyErrors($errors = TRUE) {
        static::$anyErrors = $errors;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function hasAnyErrors() {
        return static::$anyErrors;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setErrorByName($name, $message = '') {
        if ($this->isValidationComplete()) {
            throw new \LogicException('Form errors cannot be set after form validation has finished.');
        }
        $errors = $this->getErrors();
        if (!isset($errors[$name])) {
            $record = TRUE;
            $limit_validation_errors = $this->getLimitValidationErrors();
            if ($limit_validation_errors !== NULL) {
                $record = FALSE;
                foreach ($limit_validation_errors as $section) {
                    // Exploding by '][' reconstructs the element's #parents. If the
                    // reconstructed #parents begin with the same keys as the specified
                    // section, then the element's values are within the part of
                    // $form_state->getValues() that the clicked button requires to be
                    // valid, so errors for this element must be recorded. As the exploded
                    // array will all be strings, we need to cast every value of the
                    // section array to string.
                    if (array_slice(explode('][', $name), 0, count($section)) === array_map('strval', $section)) {
                        $record = TRUE;
                        break;
                    }
                }
            }
            if ($record) {
                $errors[$name] = $message;
                $this->errors = $errors;
                static::setAnyErrors();
            }
        }
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setError(array &$element, $message = '') {
        $this->setErrorByName(implode('][', $element['#parents']), $message);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function clearErrors() {
        $this->errors = [];
        static::setAnyErrors(FALSE);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getError(array $element) {
        if ($errors = $this->getErrors()) {
            $parents = [];
            foreach ($element['#parents'] as $parent) {
                $parents[] = $parent;
                $key = implode('][', $parents);
                if (isset($errors[$key])) {
                    return $errors[$key];
                }
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function getErrors() {
        return $this->errors;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setRebuild($rebuild = TRUE) {
        $this->rebuild = $rebuild;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isRebuilding() {
        return $this->rebuild;
    }
    
    /**
     * {@inheritdoc}
     */
    public function prepareCallback($callback) {
        if (is_string($callback) && substr($callback, 0, 2) == '::') {
            $callback = [
                $this->getFormObject(),
                substr($callback, 2),
            ];
        }
        return $callback;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setFormObject(FormInterface $form_object) {
        $this->addBuildInfo('callback_object', $form_object);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFormObject() {
        return $this->getBuildInfo()['callback_object'];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCleanValueKeys() {
        return $this->cleanValueKeys;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setCleanValueKeys(array $cleanValueKeys) {
        $this->cleanValueKeys = $cleanValueKeys;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function addCleanValueKey($cleanValueKey) {
        $keys = $this->getCleanValueKeys();
        $this->setCleanValueKeys(array_merge((array) $keys, [
            $cleanValueKey,
        ]));
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function cleanValues() {
        foreach ($this->getCleanValueKeys() as $value) {
            $this->unsetValue($value);
        }
        // Remove button values.
        // \Drupal::formBuilder()->doBuildForm() collects all button elements in a
        // form. We remove the button value separately for each button element.
        foreach ($this->getButtons() as $button) {
            // Remove this button's value from the submitted form values by finding
            // the value corresponding to this button.
            // We iterate over the #parents of this button and move a reference to
            // each parent in self::getValues(). For example, if #parents is:
            // @code
            //   array('foo', 'bar', 'baz')
            // @endcode
            // then the corresponding self::getValues() part will look like this:
            // @code
            // array(
            //   'foo' => array(
            //     'bar' => array(
            //       'baz' => 'button_value',
            //     ),
            //   ),
            // )
            // @endcode
            // We start by (re)moving 'baz' to $last_parent, so we are able unset it
            // at the end of the iteration. Initially, $values will contain a
            // reference to self::getValues(), but in the iteration we move the
            // reference to self::getValue('foo'), and finally to
            // self::getValue(array('foo', 'bar')), which is the level where we
            // can unset 'baz' (that is stored in $last_parent).
            $parents = $button['#parents'];
            $last_parent = array_pop($parents);
            $key_exists = NULL;
            $values =& NestedArray::getValue($this->getValues(), $parents, $key_exists);
            if ($key_exists && is_array($values)) {
                unset($values[$last_parent]);
            }
        }
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setInvalidToken($invalid_token) {
        $this->invalidToken = (bool) $invalid_token;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasInvalidToken() {
        return $this->invalidToken;
    }
    
    /**
     * Wraps ModuleHandler::loadInclude().
     */
    protected function moduleLoadInclude($module, $type, $name = NULL) {
        return \Drupal::moduleHandler()->loadInclude($module, $type, $name);
    }

}