NEW: Added replaceExistingFile setting for UploadField.

Sometimes has-one UploadFields can get confused about whether or not there is an existing file that needs deleting.  This setting lets you make a more robust has-one UploadField, where any existing file will be replaced.  It more closely mimics simple single-file upload fields.

_config/uploadfield.yml

@@ -6,6 +6,7 @@ UploadField:
     allowedMaxFileNumber:
     canUpload: true
     canAttachExisting: 'CMS_ACCESS_AssetAdmin'
+    replaceExistingFile: false
     previewMaxWidth: 80
     previewMaxHeight: 60
     uploadTemplateName: 'ss-uploadfield-uploadtemplate'

forms/UploadField.php

@@ -93,6 +93,13 @@ class UploadField extends FileField {
 		 * String values are interpreted as permission codes.
 		 */
 		'canAttachExisting' => "CMS_ACCESS_AssetAdmin",
+		/**
+		 * @var boolean If a second file is uploaded, should it replace the existing one rather than throwing an errror?
+		 * This only applies for has_one relationships, and only replaces the association
+		 * rather than the actual file database record or filesystem entry.
+		 */
+		'replaceExistingFile' => false,
+		/**
 		 * @var int
 		 */
 		'previewMaxWidth' => 80,
@@ -487,6 +494,10 @@ public function upload(SS_HTTPRequest $request) {
 				$tooManyFiles = $record->{$name}()->count() >= $this->getConfig('allowedMaxFileNumber');
 			// has_one only allows one file at any given time.
 			} elseif($record->has_one($name)) {
+				// If we're allowed to replace an existing file, clear out the old one
+				if($record->$name && $this->getConfig('replaceExistingFile')) {
+					$record->$name = null;
+				}
 				$tooManyFiles = $record->{$name}() && $record->{$name}()->exists();
 			}