From b97c5ac7dca70ada644e11294da0e38ba01a4418 Mon Sep 17 00:00:00 2001
From: neomerx <info@neomerx.com>
Date: Sat, 2 Mar 2019 19:01:31 +0300
Subject: [PATCH] Close #230

---
 src/Representation/DocumentWriter.php | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/src/Representation/DocumentWriter.php b/src/Representation/DocumentWriter.php
index f15d00e2..e2f5c292 100644
--- a/src/Representation/DocumentWriter.php
+++ b/src/Representation/DocumentWriter.php
@@ -266,21 +266,42 @@ protected function getResourceRepresentation(ResourceInterface $resource, FieldS
 
         $attributes = $this->getAttributesRepresentation($filter->getAttributes($resource));
         if (empty($attributes) === false) {
+            \assert(
+                \json_encode($attributes) !== false,
+                'Attributes for resource type `' . $resource->getType() .
+                '` cannot be converted into JSON. Please check its Schema returns valid data.'
+            );
             $representation[DocumentInterface::KEYWORD_ATTRIBUTES] = $attributes;
         }
 
         $relationships = $this->getRelationshipsRepresentation($filter->getRelationships($resource));
         if (empty($relationships) === false) {
+            \assert(
+                \json_encode($relationships) !== false,
+                'Relationships for resource type `' . $resource->getType() .
+                '` cannot be converted into JSON. Please check its Schema returns valid data.'
+            );
             $representation[DocumentInterface::KEYWORD_RELATIONSHIPS] = $relationships;
         }
 
         if ($resource->hasLinks() === true) {
-            $representation[DocumentInterface::KEYWORD_LINKS] =
-                $this->getLinksRepresentation($this->getUrlPrefix(), $resource->getLinks());
+            $links = $this->getLinksRepresentation($this->getUrlPrefix(), $resource->getLinks());
+            \assert(
+                \json_encode($links) !== false,
+                'Links for resource type `' . $resource->getType() .
+                '` cannot be converted into JSON. Please check its Schema returns valid data.'
+            );
+            $representation[DocumentInterface::KEYWORD_LINKS] = $links;
         }
 
         if ($resource->hasResourceMeta() === true) {
-            $representation[DocumentInterface::KEYWORD_META] = $resource->getResourceMeta();
+            $meta = $resource->getResourceMeta();
+            \assert(
+                \json_encode($meta) !== false,
+                'Meta for resource type `' . $resource->getType() .
+                '` cannot be converted into JSON. Please check its Schema returns valid data.'
+            );
+            $representation[DocumentInterface::KEYWORD_META] = $meta;
         }
 
         return $representation;