handle sparse fieldsets (?fields=)

src/Adapter/AdapterInterface.php

@@ -57,6 +57,13 @@ interface AdapterInterface
      */
     public function filterByExpression($query, string $expression): void;
 
+    /**
+     * Manipulate the query to only include specific fields.
+     *
+     * @param string|array $fields Comma-separated list of field names to include or array of such lists for every resource type
+     */
+    public function sparseFieldset($query, $fields): void;
+
     /**
      * Manipulate the query to sort by the given attribute in the given direction.
      */

src/Adapter/EloquentAdapter.php

@@ -65,6 +65,10 @@ class EloquentAdapter implements AdapterInterface
     {
     }
 
+    public function sparseFieldset($query, $fields): void
+    {
+    }
+
     public function sortByAttribute($query, Attribute $attribute, string $direction): void
     {
         $query->orderBy($this->getAttributeProperty($attribute), $direction);

src/Adapter/NullAdapter.php

@@ -31,6 +31,10 @@ class NullAdapter implements AdapterInterface
     {
     }
 
+    public function sparseFieldset($query, $fields): void
+    {
+    }
+
     public function sortByAttribute($query, Attribute $attribute, string $direction): void
     {
     }

src/Endpoint/Index.php

@@ -65,6 +65,10 @@ class Index
             $resourceType->applyFilters($query, $filter, $context);
         }
 
+        if ($fields = $context->getRequest()->getQueryParams()['fields'] ?? null) {
+            $resourceType->applySparseFieldset($query, $fields, $context);
+        }
+
         run_callbacks($schema->getListeners('listing'), [$query, $context]);
 
         $total = $schema->isCountable() ? $adapter->count($query) : null;

src/ResourceType.php

@@ -169,6 +169,14 @@ final class ResourceType
         }
     }
 
+    /**
+     * Apply the resource type's sparse fieldsets to a query.
+     */
+    public function applySparseFieldset($query, $fields, Context $context): void
+    {
+        $this->adapter->sparseFieldset($query, $fields);
+    }
+
     private function filterByAttribute($query, Attribute $attribute, $value): void
     {
         if (preg_match('/(.+)\.\.(.+)/', $value, $matches)) {