[11.x] Fixes through() relationship

src/Illuminate/Database/Eloquent/PendingHasThroughRelationship.php

@@ -4,6 +4,8 @@
 
 use BadMethodCallException;
 use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\MorphMany;
+use Illuminate\Database\Eloquent\Relations\MorphOneOrMany;
 use Illuminate\Support\Str;
 
 /**
@@ -44,7 +46,7 @@ public function __construct($rootModel, $localRelationship)
      *
      * @template TRelatedModel of \Illuminate\Database\Eloquent\Model
      *
-     * @param  string|(callable(TIntermediateModel): (\Illuminate\Database\Eloquent\Relations\HasOne<TRelatedModel, TIntermediateModel>|\Illuminate\Database\Eloquent\Relations\HasMany<TRelatedModel, TIntermediateModel>))  $callback
+     * @param  string|(callable(TIntermediateModel): (\Illuminate\Database\Eloquent\Relations\HasOne<TRelatedModel, TIntermediateModel>|\Illuminate\Database\Eloquent\Relations\HasMany<TRelatedModel, TIntermediateModel>|\Illuminate\Database\Eloquent\Relations\MorphOneOrMany<TRelatedModel, TIntermediateModel>))  $callback
      * @return (
      *     $callback is string
      *     ? \Illuminate\Database\Eloquent\Relations\HasManyThrough<\Illuminate\Database\Eloquent\Model, TIntermediateModel, TDeclaringModel>|\Illuminate\Database\Eloquent\Relations\HasOneThrough<\Illuminate\Database\Eloquent\Model, TIntermediateModel, TDeclaringModel>
@@ -64,24 +66,30 @@ public function has($callback)
         $distantRelation = $callback($this->localRelationship->getRelated());
 
         if ($distantRelation instanceof HasMany) {
-            return $this->rootModel->hasManyThrough(
+            $returnedRelation =  $this->rootModel->hasManyThrough(
                 $distantRelation->getRelated()::class,
                 $this->localRelationship->getRelated()::class,
                 $this->localRelationship->getForeignKeyName(),
                 $distantRelation->getForeignKeyName(),
                 $this->localRelationship->getLocalKeyName(),
                 $distantRelation->getLocalKeyName(),
             );
+        } else {
+            $returnedRelation = $this->rootModel->hasOneThrough(
+                $distantRelation->getRelated()::class,
+                $this->localRelationship->getRelated()::class,
+                $this->localRelationship->getForeignKeyName(),
+                $distantRelation->getForeignKeyName(),
+                $this->localRelationship->getLocalKeyName(),
+                $distantRelation->getLocalKeyName(),
+            );
+        }
+
+        if ($this->localRelationship instanceof MorphOneOrMany) {
+            $returnedRelation->where($this->localRelationship->getQualifiedMorphType(), $this->localRelationship->getMorphClass());
         }
 
-        return $this->rootModel->hasOneThrough(
-            $distantRelation->getRelated()::class,
-            $this->localRelationship->getRelated()::class,
-            $this->localRelationship->getForeignKeyName(),
-            $distantRelation->getForeignKeyName(),
-            $this->localRelationship->getLocalKeyName(),
-            $distantRelation->getLocalKeyName(),
-        );
+        return $returnedRelation;
     }
 
     /**

tests/Integration/Database/EloquentThroughTest.php

@@ -0,0 +1,122 @@
+<?php
+
+namespace Illuminate\Tests\Integration\Database\EloquentThroughTest;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+use Illuminate\Tests\Integration\Database\DatabaseTestCase;
+
+class EloquentThroughTest extends DatabaseTestCase
+{
+    protected function afterRefreshingDatabase()
+    {
+        Schema::create('posts', function (Blueprint $table) {
+            $table->increments('id');
+            $table->boolean('public');
+        });
+
+        Schema::create('other_commentables', function (Blueprint $table) {
+            $table->increments('id');
+        });
+
+        Schema::create('comments', function (Blueprint $table) {
+            $table->increments('id');
+            $table->string('commentable_type');
+            $table->integer('commentable_id');
+        });
+
+        Schema::create('likes', function (Blueprint $table) {
+            $table->increments('id');
+            $table->unsignedInteger('comment_id');
+        });
+
+
+        $post = tap(new Post(['public' => true]))->save();
+        $comment = tap((new Comment)->commentable()->associate($post))->save();
+        (new Like())->comment()->associate($comment)->save();
+        (new Like())->comment()->associate($comment)->save();
+
+        $otherCommentable = tap(new OtherCommentable())->save();
+        $comment2 = tap((new Comment)->commentable()->associate($otherCommentable))->save();
+        (new Like())->comment()->associate($comment2)->save();
+    }
+
+    public function test()
+    {
+        /** @var Post $post */
+        $post = Post::first();
+        $this->assertEquals(2, $post->commentLikes()->count());
+    }
+}
+
+class Comment extends Model
+{
+    public $timestamps = false;
+
+    public function commentable()
+    {
+        return $this->morphTo();
+    }
+
+    public function likes()
+    {
+        return $this->hasMany(Like::class);
+    }
+}
+
+class Post extends Model
+{
+    public $timestamps = false;
+
+    protected $guarded = [];
+
+    protected $withCount = ['comments'];
+
+    public function comments()
+    {
+        return $this->morphMany(Comment::class, 'commentable');
+    }
+
+    public function commentLikes()
+    {
+        return $this->through($this->comments())->has('likes');
+    }
+
+    public function texts()
+    {
+        return $this->hasMany(Text::class);
+    }
+}
+
+class OtherCommentable extends Model
+{
+    public $timestamps = false;
+
+    public function comments()
+    {
+        return $this->morphMany(Comment::class, 'commentable');
+    }
+}
+
+class Text extends Model
+{
+    public $timestamps = false;
+
+    protected $guarded = [];
+
+    public function post()
+    {
+        return $this->belongsTo(Post::class);
+    }
+}
+
+class Like extends Model
+{
+    public $timestamps = false;
+
+    public function comment()
+    {
+        return $this->belongsTo(Comment::class);
+    }
+}