don't open the file when handling HEAD requests

patches.txt

@@ -3,6 +3,7 @@ Patches:
 - patchwork/utf8: Remove trigger_error() that spammed the error log
 - Doctrine: fix error handling for not null columns on some mysql servers https://github.com/doctrine/dbal/pull/2422
 - SabreDAV: Make sure that files that are children of directories, are reported as files https://github.com/fruux/sabre-dav/issues/982
+- SabreDAV: Don't open the file on HEAD requests https://github.com/sabre-io/dav/pull/1058
 - SabreXML: Fix invalid PHP docs https://github.com/fruux/sabre-xml/pull/128
 - SabreXML: Prevent infinite loops for empty props element https://github.com/fruux/sabre-xml/pull/132
 - ZipStreamer: Fix zip generation for 7zip https://github.com/McNetic/PHPZipStreamer/pull/39

sabre/dav/lib/DAV/CorePlugin.php

@@ -82,14 +82,18 @@ function httpGet(RequestInterface $request, ResponseInterface $response) {
 
         if (!$node instanceof IFile) return;
 
-        $body = $node->get();
-
-        // Converting string into stream, if needed.
-        if (is_string($body)) {
-            $stream = fopen('php://temp', 'r+');
-            fwrite($stream, $body);
-            rewind($stream);
-            $body = $stream;
+        if ($request->getHeader('X-Sabre-Original-Method') === 'HEAD') {
+            $body = '';
+        } else {
+            $body = $node->get();
+
+            // Converting string into stream, if needed.
+            if (is_string($body)) {
+                $stream = fopen('php://temp', 'r+');
+                fwrite($stream, $body);
+                rewind($stream);
+                $body = $stream;
+            }
         }
 
         /*
@@ -245,13 +249,13 @@ function httpOptions(RequestInterface $request, ResponseInterface $response) {
     function httpHead(RequestInterface $request, ResponseInterface $response) {
 
         // This is implemented by changing the HEAD request to a GET request,
-        // and dropping the response body.
+        // and telling the request handler that is doesn't need to create the body.
         $subRequest = clone $request;
         $subRequest->setMethod('GET');
+        $subRequest->setHeader('X-Sabre-Original-Method', 'HEAD');
 
         try {
             $this->server->invokeMethod($subRequest, $response, false);
-            $response->setBody('');
         } catch (Exception\NotImplemented $e) {
             // Some clients may do HEAD requests on collections, however, GET
             // requests and HEAD requests _may_ not be defined on a collection,