Allow GraphQL to filter on nested property

fixes #1714, #1867

Author: antograssiot

features/graphql/filters.feature

@@ -88,3 +88,27 @@ Feature: Collections filtering
     And the JSON node "data.dummies.edges[1].node.relatedDummies.edges" should have 0 elements
     And the JSON node "data.dummies.edges[2].node.relatedDummies.edges" should have 1 element
     And the JSON node "data.dummies.edges[2].node.relatedDummies.edges[0].node.name" should be equal to "RelatedDummy13"
+
+  @createSchema
+  Scenario: Retrieve a collection filtered using the related search filter
+    Given there are 1 dummy objects having each 2 relatedDummies
+    And there are 1 dummy objects having each 3 relatedDummies
+    When I add "Accept" header equal to "application/hal+json"
+    And I send a "GET" request to "/dummies?relatedDummies.name=RelatedDummy31"
+    Then the response status code should be 200
+    And the response should be in JSON
+    And the JSON node "_embedded.item" should have 1 element
+    When I send the following GraphQL request:
+    """
+    {
+      dummies(relatedDummies_name: "RelatedDummy31") {
+        edges {
+          node {
+            id
+          }
+        }
+      }
+    }
+    """
+    And the response status code should be 200
+    And the JSON node "data.dummies.edges" should have 1 element

src/GraphQl/Resolver/Factory/CollectionResolverFactory.php

@@ -77,7 +77,14 @@ public function __invoke(string $resourceClass = null, string $rootClass = null,
             $resourceMetadata = $this->resourceMetadataFactory->create($resourceClass);
             $dataProviderContext = $resourceMetadata->getGraphqlAttribute('query', 'normalization_context', [], true);
             $dataProviderContext['attributes'] = $this->fieldsToAttributes($info);
-            $dataProviderContext['filters'] = $args;
+            $filters = $args;
+            foreach ($filters as $name => $value) {
+                if (strpos($name, '_')) {
+                    // Gives a chance to relations/nested fields
+                    $filters[str_replace('_', '.', $name)] = $value;
+                }
+            }
+            $dataProviderContext['filters'] = $filters;
 
             if (isset($rootClass, $source[$rootProperty = $info->fieldName], $source[ItemNormalizer::ITEM_KEY])) {
                 $rootResolvedFields = $this->identifiersExtractor->getIdentifiersFromItem(unserialize($source[ItemNormalizer::ITEM_KEY]));