NEW Add support for ManyManyThrough relations

Previously relationships defiend as many_many came in a special type
of RelationList - however now this can be one of two types of
RelationList depending on the type of definition, with both being
valid many_many relationships.

This had the unfortunate side effect of seeing the OrderableRows
component in (the least) cease functioning correctly. No longer.

src/GridFieldOrderableRows.php

@@ -17,8 +17,11 @@
 use SilverStripe\ORM\DataList;
 use SilverStripe\ORM\DataObject;
 use SilverStripe\ORM\DataObjectInterface;
+use SilverStripe\ORM\DataObjectSchema;
 use SilverStripe\ORM\DB;
 use SilverStripe\ORM\ManyManyList;
+use SilverStripe\ORM\ManyManyThroughList;
+use SilverStripe\ORM\ManyManyThroughQueryManipulator;
 use SilverStripe\ORM\Map;
 use SilverStripe\ORM\SS_List;
 use SilverStripe\ORM\FieldType\DBDatetime;
@@ -141,6 +144,16 @@ public function getExtraSortFields()
         return $this->extraSortFields;
     }
 
+    /**
+     * Checks to see if the relationship list is for a type of many_many
+     *
+     * @param SS_List $list
+     */
+    protected function isManyMany(SS_List $list)
+    {
+        return $list instanceof ManyManyList || $list instanceof ManyManyThroughList;
+    }
+
     /**
      * Sets extra sort fields to apply before the sort field.
      *
@@ -189,6 +202,9 @@ public function validateSortField(SS_List $list)
             if ($extra && array_key_exists($field, $extra)) {
                 return;
             }
+        } elseif ($list instanceof ManyManyThroughList) {
+            $manipulator = $this->getManyManyInspector($list);
+            return DataObject::getSchema()->tableName($manipulator->getJoinClass(), $field);
         }
 
         $classes = ClassInfo::dataClassesFor($list->dataClass());
@@ -217,6 +233,8 @@ public function getSortTable(SS_List $list)
             if ($extra && array_key_exists($field, $extra)) {
                 return $table;
             }
+        } elseif ($list instanceof ManyManyThroughList) {
+            return $this->getManyManyInspector($list)->getJoinAlias();
         }
         $classes = ClassInfo::dataClassesFor($list->dataClass());
         foreach ($classes as $class) {
@@ -340,9 +358,10 @@ public function handleReorder($grid, $request)
         }
         $list = $grid->getList();
         $modelClass = $grid->getModelClass();
-        if ($list instanceof ManyManyList && !singleton($modelClass)->canView()) {
+        $isManyMany = $this->isManyMany($list);
+        if ($isManyMany && !singleton($modelClass)->canView()) {
             $this->httpError(403);
-        } elseif (!($list instanceof ManyManyList) && !singleton($modelClass)->canEdit()) {
+        } elseif (!$isManyMany && !singleton($modelClass)->canEdit()) {
             $this->httpError(403);
         }
 
@@ -510,6 +529,16 @@ protected function executeReorder(GridField $grid, $sortedIDs)
                     $current[$record->ID] = $record->$field;
                 }
             }
+        } elseif ($items instanceof ManyManyThroughList) {
+            $manipulator = $this->getManyManyInspector($list);
+            $joinClass = $manipulator->getJoinClass();
+            $fromRelationName = $manipulator->getForeignKey();
+            $toRelationName = $manipulator->getLocalKey();
+            $list = DataList::create($joinClass)->filter([
+                $toRelationName => $items->column('ID'),
+                $fromRelationName => $items->first()->getJoin()->$fromRelationName,
+            ]);
+            $current = $list->map('ID', $field)->toArray();
         } else {
             $current = $items->map('ID', $field)->toArray();
         }
@@ -629,7 +658,7 @@ protected function populateSortValues(DataList $list)
                 $this->getSortTableClauseForIds($list, $id)
             ));
 
-            if (!$isBaseTable && !$list instanceof ManyManyList) {
+            if (!$isBaseTable && !$this->isManyMany($list)) {
                 DB::query(sprintf(
                     'UPDATE "%s" SET "LastEdited" = \'%s\' WHERE %s',
                     $baseTable,
@@ -640,6 +669,18 @@ protected function populateSortValues(DataList $list)
         }
     }
 
+    /**
+     * Forms a WHERE clause for the table the sort column is defined on.
+     * e.g. ID = 5
+     * e.g. ID IN(5, 8, 10)
+     * e.g. SortOrder = 5 AND RelatedThing.ID = 3
+     * e.g. SortOrder IN(5, 8, 10) AND RelatedThing.ID = 3
+     *
+     * @param DataList $list
+     * @param int|string|array $ids a single number, or array of numbers
+     *
+     * @return string
+     */
     protected function getSortTableClauseForIds(DataList $list, $ids)
     {
         if (is_array($ids)) {
@@ -648,10 +689,13 @@ protected function getSortTableClauseForIds(DataList $list, $ids)
             $value = '= ' . (int) $ids;
         }
 
-        if ($list instanceof ManyManyList) {
-            $extra = $list->getExtraFields();
-            $key   = $list->getLocalKey();
-            $foreignKey = $list->getForeignKey();
+        if ($this->isManyMany($list)) {
+            $intropector = $this->getManyManyInspector($list);
+            $extra = $list instanceof ManyManyList ?
+                $intropector->getExtraFields() :
+                DataObjectSchema::create()->fieldSpecs($intropector->getJoinClass(), DataObjectSchema::DB_ONLY);
+            $key   = $intropector->getLocalKey();
+            $foreignKey = $intropector->getForeignKey();
             $foreignID  = (int) $list->getForeignID();
 
             if ($extra && array_key_exists($this->getSortField(), $extra)) {
@@ -667,4 +711,27 @@ protected function getSortTableClauseForIds(DataList $list, $ids)
 
         return "\"ID\" $value";
     }
+
+    /**
+     * A ManyManyList defines functions such as getLocalKey, however on ManyManyThroughList
+     * these functions are moved to ManyManyThroughQueryManipulator, but otherwise retain
+     * the same signature.
+     *
+     * @param ManyManyList|ManyManyThroughList
+     *
+     * @return ManyManyList|ManyManyThroughQueryManipulator
+     */
+    protected function getManyManyInspector($list)
+    {
+        $inspector = $list;
+        if ($list instanceof ManyManyThroughList) {
+            foreach ($list->dataQuery()->getDataQueryManipulators() as $manipulator) {
+                if ($manipulator instanceof ManyManyThroughQueryManipulator) {
+                    $inspector = $manipulator;
+                    break;
+                }
+            }
+        }
+        return $inspector;
+    }
 }