Implemented sort clauses on type collections. Limited to metadata sort clauses.

```
{
  content {
    items(sortBy: [_datePublished, _desc, _name]) {
    }
  }
}
```

Author: Bertrand Dunogier

DomainContent/SchemaWorker/ContentType/AddDomainContentToDomainGroup.php

@@ -37,6 +37,10 @@ public function work(array &$schema, array $args)
                         'type' => "ContentSearchQuery",
                         'description' => "A Content query used to filter results"
                     ],
+                    'sortBy' => [
+                        'type' => '[SortByOptions]',
+                        'description' => "A sort clause, or array of clauses. Add _desc after a clause to reverse it"
+                    ],
                 ],
             ];
 

GraphQL/InputMapper/SearchQueryMapper.php

@@ -51,6 +51,37 @@ public function mapInputToQuery(array $inputArray)
         $criteria = array_merge($criteria, $this->mapDateMetadata($inputArray, 'Modified'));
         $criteria = array_merge($criteria, $this->mapDateMetadata($inputArray, 'Created'));
 
+        if (isset($inputArray['sortBy'])) {
+            $query->sortClauses = array_map(
+                function ($sortClauseClass) {
+                    /** @var Query\SortClause $lastSortClause */
+                    static $lastSortClause;
+
+                    if ($sortClauseClass === Query::SORT_DESC) {
+                        if (!$lastSortClause instanceof Query\SortClause) {
+                            return null;
+                        }
+
+                        $lastSortClause->direction = $sortClauseClass;
+                        return null;
+                    }
+
+                    if (!class_exists($sortClauseClass)) {
+                        return null;
+                    }
+
+                    if (!in_array(Query\SortClause::class, class_parents($sortClauseClass))) {
+                        return null;
+                    }
+
+                    return $lastSortClause = new $sortClauseClass;
+                },
+                $inputArray['sortBy']
+            );
+            // remove null entries left out because of sort direction
+            $query->sortClauses = array_filter($query->sortClauses);
+        }
+
         if (count($criteria) === 0) {
             return $query;
         }

GraphQL/Resolver/DomainContentResolver.php

@@ -95,6 +95,9 @@ private function findContentItemsByTypeIdentifier($contentTypeIdentifier, Argume
     {
         $queryArg = $args['query'];
         $queryArg['ContentTypeIdentifier'] = $contentTypeIdentifier;
+        if (isset($args['sortBy'])) {
+            $queryArg['sortBy'] = $args['sortBy'];
+        }
         $args['query'] = $queryArg;
 
         $query = $this->queryMapper->mapInputToQuery($args['query']);

Resources/config/graphql/Search.types.yml

@@ -81,4 +81,30 @@ DateCriterionOperator:
     config:
         values:
             before: {}
-            after: {}
+            after: {}
+
+SortByOptions:
+    type: enum
+    config:
+        values:
+            _contentId:
+                value: '\eZ\Publish\API\Repository\Values\Content\Query\SortClause\ContentId'
+                description: "Sort by content id"
+            _name:
+                value: '\eZ\Publish\API\Repository\Values\Content\Query\SortClause\ContentName'
+                description: "Sort by content name"
+            _dateModified:
+                value: '\eZ\Publish\API\Repository\Values\Content\Query\SortClause\DateModified'
+                description: "Sort by last modification date"
+            _datePublished:
+                value: '\eZ\Publish\API\Repository\Values\Content\Query\SortClause\DatePublished'
+                description: "Sort by initial publication date"
+            _sectionIdentifier:
+                value: '\eZ\Publish\API\Repository\Values\Content\Query\SortClause\SectionIdentifier'
+                description: "Sort by content section identifier"
+            _sectionName:
+                value: '\eZ\Publish\API\Repository\Values\Content\Query\SortClause\SectionName'
+                description: "Sort by section name"
+            _desc:
+                value: 'descending'
+                description: "Reverse the previous sorting option"