Fix issues with `ShowOrderFormField`

See #2509

diff --git a/wcfsetup/install/files/lib/system/form/builder/field/ShowOrderFormField.class.php b/wcfsetup/install/files/lib/system/form/builder/field/ShowOrderFormField.class.php
index 677ae9b85138f80071a2dcbeddd10580bf04c9eb..c6ca5f2e286a973877e432804c7c2d9c927e2799 100644 (file)
--- a/wcfsetup/install/files/lib/system/form/builder/field/ShowOrderFormField.class.php
+++ b/wcfsetup/install/files/lib/system/form/builder/field/ShowOrderFormField.class.php
@@ -1,5 +1,6 @@
 <?php
 namespace wcf\system\form\builder\field;
+use wcf\system\form\builder\IFormDocument;
 use wcf\system\form\builder\IFormNode;
 use wcf\system\WCF;
 
@@ -14,6 +15,14 @@ use wcf\system\WCF;
  * This field uses the `wcf.form.field.showOrder` language item as the default form
  * field label uses `showOrder` as the default node id.
  * 
+ * While the options of the field work with the ids of the appropriate sibling objects
+ * as keys, the value of the field is the actual position of the relevant object (from
+ * `1` to `count($siblings)`.
+ * 
+ * If an object is edited, thus `$this->getDocument()->getFormMode() === IFormDocument::FORM_MODE_UPDATE`,
+ * it is expected that the edited objects itself is not part of the sibling list provided
+ * for the field options.
+ * 
  * @author     Matthias Schmidt
  * @copyright  2001-2018 WoltLab GmbH
  * @license    GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
@@ -32,7 +41,7 @@ class ShowOrderFormField extends SingleSelectionFormField {
         * @inheritDoc
         */
        public function getSaveValue() {
-               if ($this->__value) {
+               if ($this->__value !== null) {
                        $index = array_search($this->__value, array_keys($this->getOptions()));
                        
                        if ($index !== false) {
@@ -56,10 +65,8 @@ class ShowOrderFormField extends SingleSelectionFormField {
        public function options($options): ISelectionFormField {
                parent::options($options);
                
-               $this->__options = array_merge(
-                       [0 => WCF::getLanguage()->get('wcf.form.field.showOrder.firstPosition')],
-                       $this->__options
-               );
+               $this->__options = [0 => WCF::getLanguage()->get('wcf.form.field.showOrder.firstPosition')] + $this->__options;
+               $this->possibleValues[] = 0;
                
                return $this;
        }
@@ -70,7 +77,13 @@ class ShowOrderFormField extends SingleSelectionFormField {
        public function value($value): IFormField {
                $keys = array_keys($this->getOptions());
                
-               if (count($keys) < $value) {
+               // when editing an objects, the value has to be reduced by one to determine the
+               // relevant sibling as the edited object is shown after its previous sibling 
+               if ($this->getDocument()->getFormMode() === IFormDocument::FORM_MODE_UPDATE) {
+                       $value -= 1;
+               }
+               
+               if (count($keys) <= $value) {
                        throw new \InvalidArgumentException("Unknown value '{$value}' as only " . count($keys) . " values are available.");
                }