Implement canAdopt() in IFileProcessor and FileProcessor

wcfsetup/install/files/lib/system/endpoint/controller/core/files/upload/SaveChunk.class.php

@@ -12,6 +12,7 @@
 use wcf\system\endpoint\IController;
 use wcf\system\endpoint\PostRequest;
 use wcf\system\exception\UserInputException;
+use wcf\system\file\processor\FileProcessor;
 use wcf\system\io\File;
 
 #[PostRequest('/core/files/upload/{identifier}/chunk/{sequenceNo:\d+}')]
@@ -118,9 +119,11 @@ public function __invoke(ServerRequestInterface $request, array $variables): Res
 
                     throw new UserInputException('validation', $exception->getType());
                 }
-            }
 
-            $processor?->adopt($file, $context);
+                if (FileProcessor::getInstance()->canAdopt($processor, $file, $context)) {
+                    $processor->adopt($file, $context);
+                }
+            }
 
             $generateThumbnails = false;
             if ($processor !== null && $file->isImage()) {

wcfsetup/install/files/lib/system/file/processor/AttachmentFileProcessor.class.php

@@ -40,6 +40,12 @@ public function getAllowedFileExtensions(array $context): array
         return $attachmentHandler->getAllowedExtensions();
     }
 
+    #[\Override]
+    public function canAdopt(File $file, array $context): bool
+    {
+        return Attachment::findByFileID($file->fileID) === null;
+    }
+
     #[\Override]
     public function adopt(File $file, array $context): void
     {

wcfsetup/install/files/lib/system/file/processor/FileProcessor.class.php

@@ -125,6 +125,16 @@ public function getHtmlElement(IFileProcessor $fileProcessor, array $context): s
         );
     }
 
+    public function canAdopt(IFileProcessor $fileProcessor, File $file, array $context): bool
+    {
+        $objectType = $this->getObjectType($fileProcessor->getObjectTypeName());
+        if ($objectType->objectTypeID !== $file->objectTypeID) {
+            return false;
+        }
+
+        return $fileProcessor->canAdopt($file, $context);
+    }
+
     public function generateWebpVariant(File $file): void
     {
         $canGenerateThumbnail = match ($file->mimeType) {

wcfsetup/install/files/lib/system/file/processor/IFileProcessor.class.php

@@ -36,12 +36,22 @@ public function acceptUpload(string $filename, int $fileSize, array $context): F
      */
     public function validateUpload(File $file): void;
 
+    /**
+     * Checks if the given `$file` can be assigned to the object referenced by the information
+     * contained in `$context`.
+     *
+     * The `$file` can be assigned if one of the following conditions is met:
+     * - The file has not yet been assigned to any object
+     * - The file is already assigned to the object referenced by `$context`
+     */
+    public function canAdopt(File $file, array $context): bool;
+
     /**
      * Notifies the file processor that the upload of a file has been completed
      * that belongs to this type.
      *
      * `$context` are the exact same values that have previously been passed to
-     * `acceptUpload()` before.
+     * `canAdopt()` before.
      */
     public function adopt(File $file, array $context): void;
 

wcfsetup/install/files/lib/system/form/builder/field/FileProcessorFormField.class.php

@@ -194,7 +194,7 @@ public function validate()
             $this->addValidationError(
                 new FormFieldValidationError(
                     'maximumFiles',
-                    'wcf.form.field.fileProcessor.error.maximumFiles',
+                    'wcf.upload.error.maximumCountReached',
                     [
                         'maximumCount' => $fileProcessor->getMaximumCount($this->context),
                         'count' => \count($this->files),
@@ -203,6 +203,18 @@ public function validate()
             );
         }
 
+        foreach ($this->files as $file) {
+            if (!FileProcessor::getInstance()->canAdopt($fileProcessor, $file, $this->context)) {
+                $this->addValidationError(
+                    new FormFieldValidationError(
+                        'adopt',
+                        'wcf.upload.error.adopt',
+                        ['filename' => $file->filename]
+                    )
+                );
+            }
+        }
+
         parent::validate();
     }
 

wcfsetup/install/lang/de.xml

@@ -5566,6 +5566,7 @@ Benachrichtigungen auf <a href="{link isHtmlEmail=true}{/link}">{PAGE_TITLE|phra
 		<item name="wcf.upload.error.fileExtensionNotPermitted"><![CDATA[Der Dateityp von „{$filename}“ ist unzulässig.]]></item>
 		<item name="wcf.upload.error.fileSizeTooLarge"><![CDATA[Die Datei ist zu groß.]]></item>
 		<item name="wcf.upload.error.maximumCountReached"><![CDATA[Es {plural value=$maximumCount 1='darf nur eine Datei' other='dürfen nur # Dateien'} hochgeladen werden.]]></item>
+		<item name="wcf.upload.error.adopt"><![CDATA[Die Datei „{$filename}“ kann nicht zugewiesen werden.]]></item>
 	</category>
 </import>
 <delete>

wcfsetup/install/lang/en.xml

@@ -5568,6 +5568,7 @@ your notifications on <a href="{link isHtmlEmail=true}{/link}">{PAGE_TITLE|phras
 		<item name="wcf.upload.error.fileExtensionNotPermitted"><![CDATA[The file type of “{$filename}” is not permitted.]]></item>
 		<item name="wcf.upload.error.fileSizeTooLarge"><![CDATA[The file is too large.]]></item>
 		<item name="wcf.upload.error.maximumCountReached"><![CDATA[{plural value=$maximumCount 1='Only one file' other='Only up to # files'} may be uploaded.]]></item>
+		<item name="wcf.upload.error.adopt"><![CDATA[The file „{$filename}“ cannot be assigned.]]></item>
 	</category>
 </import>
 <delete>