[BrowserKit] Fix submitting forms with empty file fields

Author: nicolas-grekas

HttpBrowser.php

@@ -143,10 +143,15 @@ private function getUploadedFiles(array $files): array
             }
             if (!isset($file['tmp_name'])) {
                 $uploadedFiles[$name] = $this->getUploadedFiles($file);
+                continue;
             }
-            if (isset($file['tmp_name'])) {
-                $uploadedFiles[$name] = DataPart::fromPath($file['tmp_name'], $file['name']);
+
+            if ('' === $file['tmp_name']) {
+                $uploadedFiles[$name] = new DataPart('', '');
+                continue;
             }
+
+            $uploadedFiles[$name] = DataPart::fromPath($file['tmp_name'], $file['name']);
         }
 
         return $uploadedFiles;

Tests/HttpBrowserTest.php

@@ -14,6 +14,8 @@
 use Symfony\Component\BrowserKit\CookieJar;
 use Symfony\Component\BrowserKit\History;
 use Symfony\Component\BrowserKit\HttpBrowser;
+use Symfony\Component\HttpClient\MockHttpClient;
+use Symfony\Component\HttpClient\Response\MockResponse;
 use Symfony\Contracts\HttpClient\HttpClientInterface;
 use Symfony\Contracts\HttpClient\ResponseInterface;
 
@@ -208,6 +210,37 @@ public static function forwardSlashesRequestPathProvider()
         ];
     }
 
+    public function testEmptyUpload()
+    {
+        $client = new MockHttpClient(function ($method, $url, $options) {
+            $this->assertSame('POST', $method);
+            $this->assertSame('http://localhost/', $url);
+            $this->assertStringStartsWith('Content-Type: multipart/form-data; boundary=', $options['normalized_headers']['content-type'][0]);
+
+            $body = '';
+            while ('' !== $data = $options['body'](1024)) {
+                $body .= $data;
+            }
+
+            $expected = <<<EOTXT
+                --%s\r
+                Content-Type: application/octet-stream\r
+                Content-Transfer-Encoding: 8bit\r
+                Content-Disposition: form-data; name="file"; filename=""\r
+                \r
+                \r
+                --%s--\r
+
+                EOTXT;
+            $this->assertStringMatchesFormat($expected, $body);
+
+            return new MockResponse();
+        });
+
+        $browser = new HttpBrowser($client);
+        $browser->request('POST', '/', [], ['file' => ['tmp_name' => '', 'name' => 'file']]);
+    }
+
     private function uploadFile(string $data): string
     {
         $path = tempnam(sys_get_temp_dir(), 'http');