Many many through syntax support added.

src/DataFormatter/JSONDataFormatter.php

@@ -2,6 +2,7 @@
 
 namespace SilverStripe\RestfulServer\DataFormatter;
 
+use SilverStripe\RestfulServer\RestfulServer;
 use SilverStripe\View\ArrayData;
 use SilverStripe\Core\Convert;
 use SilverStripe\RestfulServer\DataFormatter;
@@ -124,6 +125,8 @@ class JSONDataFormatter extends DataFormatter
             }
 
             foreach ($obj->hasMany() + $obj->manyMany() as $relName => $relClass) {
+                $relClass = RestfulServer::parseRelationClass($relClass);
+
                 //remove dot notation from relation names
                 $parts = explode('.', $relClass);
                 $relClass = array_shift($parts);

src/DataFormatter/XMLDataFormatter.php

@@ -10,6 +10,7 @@ use SilverStripe\ORM\DataObject;
 use SilverStripe\ORM\DataObjectInterface;
 use SilverStripe\Control\Director;
 use SilverStripe\ORM\SS_List;
+use SilverStripe\RestfulServer\RestfulServer;
 
 /**
  * Formats a DataObject's member fields into an XML string
@@ -196,6 +197,8 @@ class XMLDataFormatter extends DataFormatter
             }
 
             foreach ($obj->manyMany() as $relName => $relClass) {
+                $relClass = RestfulServer::parseRelationClass($relClass);
+
                 //remove dot notation from relation names
                 $parts = explode('.', $relClass);
                 $relClass = array_shift($parts);

src/RestfulServer.php

@@ -122,6 +122,32 @@ class RestfulServer extends Controller
         return str_replace('-', '\\', $className);
     }
 
+    /**
+     * Parse many many relation class (works with through array syntax)
+     *
+     * @param string|array $class
+     * @return string|array
+     */
+    public static function parseRelationClass($class)
+    {
+        // detect many many through syntax
+        if (is_array($class)
+            && array_key_exists('through', $class)
+            && array_key_exists('to', $class)
+        ) {
+            $toRelation = $class['to'];
+
+            $hasOne = Config::inst()->get($class['through'], 'has_one');
+            if (empty($hasOne) || !is_array($hasOne) || !array_key_exists($toRelation, $hasOne)) {
+                return $class;
+            }
+
+            return $hasOne[$toRelation];
+        }
+
+        return $class;
+    }
+
     /**
      * This handler acts as the switchboard for the controller.
      * Since no $Action url-param is set, all requests are sent here.
@@ -802,6 +828,8 @@ class RestfulServer extends Controller
         $relations = (array)$obj->hasOne() + (array)$obj->hasMany() + (array)$obj->manyMany();
         if ($relations) {
             foreach ($relations as $relName => $relClass) {
+                $relClass = static::parseRelationClass($relClass);
+
                 //remove dot notation from relation names
                 $parts = explode('.', $relClass);
                 $relClass = array_shift($parts);

tests/unit/RestfulServerTest.php

@@ -2,6 +2,7 @@
 
 namespace SilverStripe\RestfulServer\Tests;
 
+use SilverStripe\RestfulServer\RestfulServer;
 use SilverStripe\RestfulServer\Tests\Stubs\RestfulServerTestComment;
 use SilverStripe\RestfulServer\Tests\Stubs\RestfulServerTestExceptionThrown;
 use SilverStripe\RestfulServer\Tests\Stubs\RestfulServerTestSecretThing;
@@ -701,4 +702,17 @@ class RestfulServerTest extends SapphireTest
         $responseArr = Convert::xml2array($response->getBody());
         $this->assertEquals(\Exception::class, $responseArr['type']);
     }
+
+    public function testParseClassName()
+    {
+        $manyMany = RestfulServerTestAuthor::config()->get('many_many');
+
+        // simple syntax (many many standard)
+        $className = RestfulServer::parseRelationClass($manyMany['RelatedPages']);
+        $this->assertEquals(RestfulServerTestPage::class, $className);
+
+        // array syntax (many many through)
+        $className = RestfulServer::parseRelationClass($manyMany['SortedPages']);
+        $this->assertEquals(RestfulServerTestPage::class, $className);
+    }
 }

tests/unit/Stubs/AuthorSortedPageRelation.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace SilverStripe\RestfulServer\Tests\Stubs;
+
+use SilverStripe\Dev\TestOnly;
+use SilverStripe\ORM\DataObject;
+
+class AuthorSortedPageRelation extends DataObject implements TestOnly
+{
+    /**
+     * @var string
+     */
+    private static $table_name = 'AuthorSortedPageRelation';
+
+    /**
+     * @var array
+     */
+    private static $has_one = [
+        'Parent' => RestfulServerTestAuthor::class,
+        'SortedPage' => RestfulServerTestPage::class,
+    ];
+
+    /**
+     * @var array
+     */
+    private static $db = [
+        'Sort' => 'Int',
+    ];
+}

tests/unit/Stubs/RestfulServerTestAuthor.php

@@ -18,11 +18,17 @@ class RestfulServerTestAuthor extends DataObject implements TestOnly
     private static $many_many = array(
         'RelatedPages' => RestfulServerTestPage::class,
         'RelatedAuthors' => RestfulServerTestAuthor::class,
+        'SortedPages' => [
+            'through' => AuthorSortedPageRelation::class,
+            'from' => 'Parent',
+            'to' => 'SortedPage',
+        ],
     );
 
     private static $has_many = array(
         'PublishedPages' => RestfulServerTestPage::class,
         'Ratings' => RestfulServerTestAuthorRating::class,
+        'SortedPagesRelation' => AuthorSortedPageRelation::class . '.Parent',
     );
 
     public function canView($member = null)