Don't assume that file binary exists on *nix OS

teohhanhui · teohhanhui · commit e2c1f24fbd17 · 2018-04-17T11:15:40.000+02:00
Certain lightweight distributions such as Alpine Linux (popular for smaller Docker images) do not include it by default.
diff --git a/src/Symfony/Component/HttpFoundation/File/MimeType/FileBinaryMimeTypeGuesser.php b/src/Symfony/Component/HttpFoundation/File/MimeType/FileBinaryMimeTypeGuesser.php
@@ -43,7 +43,21 @@ public function __construct($cmd = 'file -b --mime %s 2>/dev/null')
      */
     public static function isSupported()
     {
-        return '\\' !== DIRECTORY_SEPARATOR && function_exists('passthru') && function_exists('escapeshellarg');
+        static $supported = null;
+
+        if (null !== $supported) {
+            return $supported;
+        }
+
+        if ('\\' === DIRECTORY_SEPARATOR || !function_exists('passthru') || !function_exists('escapeshellarg')) {
+            return $supported = false;
+        }
+
+        ob_start();
+        passthru('command -v file', $exitStatus);
+        $binPath = trim(ob_get_clean());
+
+        return $supported = 0 === $exitStatus && '' !== $binPath;
     }
 
     /**
