Add Eloquent Collection loadMorph()

Allow nested relations to be eager loaded for
morphTo() relationships of mixed classes.

e.g.,

class ActivityFeed
{
    function parentable()
    {
        return $this->morphTo();
    }
}

$collection = ActivityFeed::with('parentable')
    ->get()
    ->loadMorph('parentable', [
        Event::class => 'calendar',
        Photo::class => 'tags',
        Post::class => ['author', 'commentsCount'],
    ]);

or

$paginator = ActivityFeed::with('parentable')
    ->paginate()
    ->loadMorph('parentable', [
        // etc.
    ]);

src/Illuminate/Database/Eloquent/Collection.php

@@ -62,6 +62,30 @@ public function load($relations)
         return $this;
     }
 
+    /**
+     * Load a set of relationships onto the mixed relationship collection.
+     *
+     * @param  string $relation
+     * @param  array  $relations
+     * @return $this
+     */
+    public function loadMorph($relation, $relations)
+    {
+        $this->pluck($relation)
+            ->groupBy(function ($model) {
+                return get_class($model);
+            })
+            ->filter(function ($models, $className) use ($relations) {
+                return Arr::has($relations, $className);
+            })
+            ->each(function ($models, $className) use ($relations) {
+                $className::with($relations[$className])
+                    ->eagerLoadRelations($models->all());
+            });
+
+        return $this;
+    }
+
     /**
      * Add an item to the collection.
      *

src/Illuminate/Pagination/AbstractPaginator.php

@@ -521,6 +521,20 @@ public function setCollection(Collection $collection)
         return $this;
     }
 
+    /**
+     * Load a set of relationships onto the mixed relationship collection.
+     *
+     * @param  string $relation
+     * @param  array  $relations
+     * @return $this
+     */
+    public function loadMorph($relation, $relations)
+    {
+        $this->getCollection()->loadMorph($relation, $relations);
+
+        return $this;
+    }
+
     /**
      * Determine if the given item exists.
      *

tests/Database/DatabaseEloquentPolymorphicIntegrationTest.php

@@ -4,7 +4,6 @@
 
 use PHPUnit\Framework\TestCase;
 use Illuminate\Database\Connection;
-use Illuminate\Database\Query\Builder;
 use Illuminate\Database\Capsule\Manager as DB;
 use Illuminate\Database\Eloquent\Model as Eloquent;
 
@@ -119,6 +118,26 @@ public function testItLoadsNestedRelationshipsOnDemand()
         $this->assertEquals(TestUser::first(), $like->likeable->owner);
     }
 
+    public function testItLoadsNestedMorphRelationshipsOnDemand()
+    {
+        $this->seedData();
+
+        TestPost::first()->likes()->create([]);
+
+        $likes = TestLike::with('likeable.owner')->get()->loadMorph('likeable', [
+            TestComment::class => ['commentable'],
+            TestPost::class => 'comments',
+        ]);
+
+        $this->assertTrue($likes[0]->relationLoaded('likeable'));
+        $this->assertTrue($likes[0]->likeable->relationLoaded('owner'));
+        $this->assertTrue($likes[0]->likeable->relationLoaded('commentable'));
+
+        $this->assertTrue($likes[1]->relationLoaded('likeable'));
+        $this->assertTrue($likes[1]->likeable->relationLoaded('owner'));
+        $this->assertTrue($likes[1]->likeable->relationLoaded('comments'));
+    }
+
     /**
      * Helpers...
      */
@@ -144,7 +163,7 @@ protected function connection()
     /**
      * Get a schema builder instance.
      *
-     * @return Schema\Builder
+     * @return \Illuminate\Database\Schema\Builder
      */
     protected function schema()
     {
@@ -183,6 +202,11 @@ public function owner()
     {
         return $this->belongsTo(TestUser::class, 'user_id');
     }
+
+    public function likes()
+    {
+        return $this->morphMany(TestLike::class, 'likeable');
+    }
 }
 
 /**

tests/Pagination/PaginatorLoadMorphTest.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace Illuminate\Tests\Pagination;
+
+use Mockery;
+use PHPUnit\Framework\TestCase;
+use Illuminate\Database\Eloquent\Collection;
+use Illuminate\Pagination\AbstractPaginator;
+
+class PaginatorLoadMorphTest extends TestCase
+{
+    public function testCollectionLoadMorphCanChainOnThePaginator()
+    {
+        $relations = [
+            'App\\User' => 'photos',
+            'App\\Company' => ['employees', 'calendars'],
+        ];
+
+        $items = Mockery::mock(Collection::class);
+        $items->shouldReceive('loadMorph')->with('parentable', $relations);
+
+        $p = (new class extends AbstractPaginator {})->setCollection($items);
+
+        $this->assertSame($p, $p->loadMorph('parentable', $relations));
+    }
+}