Return and use isPreviewAvailable for share previews

Since the mime type is known, now isPreviewAvailable is returned as well
and used by the JS side to properly render mime icon and previews.

apps/files_sharing/js/sharedfilelist.js

@@ -166,11 +166,10 @@
 					}
 					else {
 						file.type = 'file';
-						// force preview retrieval as we don't have mime types,
-						// the preview endpoint will fall back to the mime type
-						// icon if no preview exists
-						file.isPreviewAvailable = true;
-						file.icon = true;
+						if (share.isPreviewAvailable) {
+							file.icon = true;
+							file.isPreviewAvailable = true;
+						}
 					}
 					file.share = {
 						id: share.id,

apps/files_sharing/lib/api.php

@@ -60,6 +60,9 @@ class Api {
 			foreach ($shares as &$share) {
 				if ($share['item_type'] === 'file' && isset($share['path'])) {
 					$share['mimetype'] = \OC_Helper::getFileNameMimeType($share['path']);
+					if (\OC::$server->getPreviewManager()->isMimeSupported($share['mimetype'])) {
+						$share['isPreviewAvailable'] = true;
+					}
 				}
 				$newShares[] = $share;
 			}
@@ -214,6 +217,9 @@ class Api {
 			foreach ($shares as &$share) {
 				if ($share['item_type'] === 'file') {
 					$share['mimetype'] = \OC_Helper::getFileNameMimeType($share['file_target']);
+					if (\OC::$server->getPreviewManager()->isMimeSupported($share['mimetype'])) {
+						$share['isPreviewAvailable'] = true;
+					}
 				}
 			}
 			$result = new \OC_OCS_Result($shares);