[8.x] MorphTo relationship eager loading constraints

src/Illuminate/Database/Eloquent/Relations/MorphTo.php

@@ -51,6 +51,13 @@ class MorphTo extends BelongsTo
      */
     protected $morphableEagerLoadCounts = [];
 
+    /**
+     * A map of constraints to apply for each individual morph type.
+     *
+     * @var array
+     */
+    protected $morphableConstraints = [];
+
     /**
      * Create a new morph to relationship instance.
      *
@@ -133,6 +140,10 @@ protected function getResultsByType($type)
                                 (array) ($this->morphableEagerLoadCounts[get_class($instance)] ?? [])
                             );
 
+        if ($callback = $this->morphableConstraints[get_class($instance)] ?? null) {
+            $callback($query);
+        }
+
         $whereIn = $this->whereInMethod($instance, $ownerKey);
 
         return $query->{$whereIn}(
@@ -312,6 +323,21 @@ public function morphWithCount(array $withCount)
         return $this;
     }
 
+    /**
+     * Specify constraints on the query for a given morph type.
+     *
+     * @param  array  $with
+     * @return \Illuminate\Database\Eloquent\Relations\MorphTo
+     */
+    public function constrain(array $callbacks)
+    {
+        $this->morphableConstraints = array_merge(
+            $this->morphableConstraints, $callbacks
+        );
+
+        return $this;
+    }
+
     /**
      * Replay stored macro calls on the actual related instance.
      *

tests/Integration/Database/EloquentMorphConstrainTest.php

@@ -0,0 +1,93 @@
+<?php
+
+namespace Illuminate\Tests\Integration\Database\EloquentMorphConstrainTest;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\MorphTo;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+use Illuminate\Tests\Integration\Database\DatabaseTestCase;
+
+/**
+ * @group integration
+ */
+class EloquentMorphConstrainTest extends DatabaseTestCase
+{
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        Schema::create('posts', function (Blueprint $table) {
+            $table->increments('id');
+            $table->boolean('post_visible');
+        });
+
+        Schema::create('videos', function (Blueprint $table) {
+            $table->increments('id');
+            $table->boolean('video_visible');
+        });
+
+        Schema::create('comments', function (Blueprint $table) {
+            $table->increments('id');
+            $table->string('commentable_type');
+            $table->integer('commentable_id');
+        });
+
+        $post1 = Post::create(['post_visible' => true]);
+        (new Comment)->commentable()->associate($post1)->save();
+
+        $post2 = Post::create(['post_visible' => false]);
+        (new Comment)->commentable()->associate($post2)->save();
+
+        $video1 = Video::create(['video_visible' => true]);
+        (new Comment)->commentable()->associate($video1)->save();
+
+        $video2 = Video::create(['video_visible' => false]);
+        (new Comment)->commentable()->associate($video2)->save();
+    }
+
+    public function testMorphConstraints()
+    {
+        $comments = Comment::query()
+            ->with(['commentable' => function (MorphTo $morphTo) {
+                $morphTo->constrain([
+                    Post::class => function ($query) {
+                        $query->where('post_visible', true);
+                    },
+                    Video::class => function ($query) {
+                        $query->where('video_visible', true);
+                    },
+                ]);
+            }])
+            ->get();
+
+        $this->assertTrue($comments[0]->commentable->post_visible);
+        $this->assertNull($comments[1]->commentable);
+        $this->assertTrue($comments[2]->commentable->video_visible);
+        $this->assertNull($comments[3]->commentable);
+    }
+}
+
+class Comment extends Model
+{
+    public $timestamps = false;
+
+    public function commentable()
+    {
+        return $this->morphTo();
+    }
+}
+
+class Post extends Model
+{
+    public $timestamps = false;
+    protected $fillable = ['post_visible'];
+    protected $casts = ['post_visible' => 'boolean'];
+}
+
+class Video extends Model
+{
+    public $timestamps = false;
+    protected $fillable = ['video_visible'];
+    protected $casts = ['video_visible' => 'boolean'];
+}