Always read out warnings from the ValidatingArrayLoader

src/Composer/Util/ConfigValidator.php

@@ -107,9 +107,10 @@ class ConfigValidator
             $loader->load($manifest);
         } catch (InvalidPackageException $e) {
             $errors = array_merge($errors, $e->getErrors());
-            $warnings = array_merge($warnings, $e->getWarnings());
         }
 
+        $warnings = array_merge($warnings, $loader->getWarnings());
+
         return array($errors, $publishErrors, $warnings);
     }
 }