Fix Phriction document move on to existing document placeholder

Summary:
Looks like the logic was there already but some minor parts were missing.
Fixes T8082.

Test Plan:
- Create document `/w/foo`
- Delete document `/w/foo`
- Create document `/w/bar`
- Move document `/w/bar` for `/w/foo`
No error was displayed and document `/w/bar` was moved to `/w/foo`.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin

Maniphest Tasks: T8082

Differential Revision: https://secure.phabricator.com/D16713

src/applications/phriction/controller/PhrictionMoveController.php

@@ -31,11 +31,11 @@ final class PhrictionMoveController extends PhrictionController {
     if ($request->isFormPost()) {
       $v_note = $request->getStr('description');
       $v_slug = $request->getStr('slug');
+      $normal_slug = PhabricatorSlug::normalize($v_slug);
 
       // If what the user typed isn't what we're actually using, warn them
       // about it.
       if (strlen($v_slug)) {
-        $normal_slug = PhabricatorSlug::normalize($v_slug);
         $no_slash_slug = rtrim($normal_slug, '/');
         if ($normal_slug !== $v_slug && $no_slash_slug !== $v_slug) {
           return $this->newDialog()
@@ -66,9 +66,21 @@ final class PhrictionMoveController extends PhrictionController {
       $xactions[] = id(new PhrictionTransaction())
         ->setTransactionType(PhrictionTransaction::TYPE_MOVE_TO)
         ->setNewValue($document);
+      $target_document = id(new PhrictionDocumentQuery())
+        ->setViewer(PhabricatorUser::getOmnipotentUser())
+        ->withSlugs(array($normal_slug))
+        ->needContent(true)
+        ->requireCapabilities(
+          array(
+            PhabricatorPolicyCapability::CAN_VIEW,
+            PhabricatorPolicyCapability::CAN_EDIT,
+          ))
+        ->executeOne();
+      if (!$target_document) {
         $target_document = PhrictionDocument::initializeNewDocument(
           $viewer,
           $v_slug);
+      }
       try {
         $editor->applyTransactions($target_document, $xactions);
         $redir_uri = PhrictionDocument::getSlugURI(

src/applications/phriction/editor/PhrictionTransactionEditor.php

@@ -588,6 +588,7 @@ final class PhrictionTransactionEditor
           // Prevent overwrites and no-op moves.
           $exists = PhrictionDocumentStatus::STATUS_EXISTS;
           if ($target_document) {
+            $message = null;
             if ($target_document->getSlug() == $source_document->getSlug()) {
               $message = pht(
                 'You can not move a document to its existing location. '.
@@ -598,7 +599,7 @@ final class PhrictionTransactionEditor
                 'overwrite an existing document which is already at that '.
                 'location. Move or delete the existing document first.');
             }
-
+            if ($message !== null) {
               $error = new PhabricatorApplicationTransactionValidationError(
                 $type,
                 pht('Invalid'),
@@ -606,6 +607,7 @@ final class PhrictionTransactionEditor
                 $xaction);
               $errors[] = $error;
             }
+          }
           break;
 
         case PhrictionTransaction::TYPE_DELETE: