magento graphql-ce#970 Cannot return several errors for one GraphQL request

lib/internal/Magento/Framework/GraphQl/Exception/GraphQlInputException.php

@@ -7,13 +7,15 @@
 
 namespace Magento\Framework\GraphQl\Exception;
 
-use Magento\Framework\Exception\InputException;
+use Magento\Framework\Exception\AggregateExceptionInterface;
+use Magento\Framework\Exception\LocalizedException;
 use Magento\Framework\Phrase;
+use GraphQL\Error\ClientAware;
 
 /**
  * Exception for GraphQL to be thrown when user supplies invalid input
  */
-class GraphQlInputException extends InputException implements \GraphQL\Error\ClientAware
+class GraphQlInputException extends LocalizedException implements AggregateExceptionInterface, ClientAware
 {
     const EXCEPTION_CATEGORY = 'graphql-input';
 
@@ -22,6 +24,13 @@ class GraphQlInputException extends InputException implements \GraphQL\Error\Cli
      */
     private $isSafe;
 
+    /**
+     * The array of errors that have been added via the addError() method
+     *
+     * @var \Magento\Framework\Exception\LocalizedException[]
+     */
+    private $errors = [];
+
     /**
      * Initialize object
      *
@@ -51,4 +60,22 @@ public function getCategory() : string
     {
         return self::EXCEPTION_CATEGORY;
     }
+
+    /**
+     * @param LocalizedException $exception
+     * @return $this
+     */
+    public function addError(LocalizedException $exception): self
+    {
+        $this->errors[] = $exception;
+        return $this;
+    }
+
+    /**
+     * @return LocalizedException[]
+     */
+    public function getErrors(): array
+    {
+        return $this->errors;
+    }
 }

lib/internal/Magento/Framework/GraphQl/Query/ErrorHandler.php

@@ -7,7 +7,7 @@
 
 namespace Magento\Framework\GraphQl\Query;
 
-use GraphQL\Error\ClientAware;
+use Magento\Framework\Exception\AggregateExceptionInterface;
 use Psr\Log\LoggerInterface;
 
 /**
@@ -36,13 +36,20 @@ public function __construct(
      */
     public function handle(array $errors, callable $formatter): array
     {
-        return array_map(
-            function (ClientAware $error) use ($formatter) {
-                $this->logger->error($error);
-
-                return $formatter($error);
-            },
-            $errors
-        );
+        $formattedErrors = [];
+        foreach ($errors as $error) {
+            $this->logger->error($error);
+            $previousError = $error->getPrevious();
+            if ($previousError instanceof AggregateExceptionInterface && !empty($previousError->getErrors())) {
+                $aggregatedErrors = $previousError->getErrors();
+                foreach ($aggregatedErrors as $aggregatedError) {
+                    $this->logger->error($aggregatedError);
+                    $formattedErrors[] = $formatter($aggregatedError);
+                }
+            } else {
+                $formattedErrors[] = $formatter($error);
+            }
+        }
+        return $formattedErrors;
     }
 }