[8.x] Add whereBelongsTo() Eloquent builder method

src/Illuminate/Database/Eloquent/Builder.php

@@ -8,6 +8,7 @@
 use Illuminate\Contracts\Support\Arrayable;
 use Illuminate\Database\Concerns\BuildsQueries;
 use Illuminate\Database\Concerns\ExplainsQueries;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\BelongsToMany;
 use Illuminate\Database\Eloquent\Relations\Relation;
 use Illuminate\Database\Query\Builder as QueryBuilder;
@@ -305,6 +306,42 @@ public function orWhere($column, $operator = null, $value = null)
         return $this->where($column, $operator, $value, 'or');
     }
 
+    /**
+     * Add a "BelongsTo" relationship where clause to the query.
+     *
+     * @param  \Illuminate\Database\Eloquent\Model  $related
+     * @param  string  $relationship
+     * @param  string  $boolean
+     * @return $this
+     *
+     * @throws \Exception
+     */
+    public function whereBelongsTo($related, $relationshipName = null, $boolean = 'and')
+    {
+        if ($relationshipName === null) {
+            $relationshipName = Str::camel(class_basename(get_class($related)));
+        }
+
+        try {
+            $relationship = $this->model->{$relationshipName}();
+        } catch (BadMethodCallException $exception) {
+            throw RelationNotFoundException::make($this->model, $relationshipName);
+        }
+
+        if (! $relationship instanceof BelongsTo) {
+            throw RelationNotFoundException::make($this->model, $relationshipName, BelongsTo::class);
+        }
+
+        $this->where(
+            $relationship->getForeignKeyName(),
+            '=',
+            $related->getAttributeValue($relationship->getOwnerKeyName()),
+            $boolean,
+        );
+
+        return $this;
+    }
+
     /**
      * Add an "order by" clause for a timestamp to the query.
      *

src/Illuminate/Database/Eloquent/RelationNotFoundException.php

@@ -25,13 +25,18 @@ class RelationNotFoundException extends RuntimeException
      *
      * @param  object  $model
      * @param  string  $relation
+     * @param  string  $type
      * @return static
      */
-    public static function make($model, $relation)
+    public static function make($model, $relation, $type = null)
     {
         $class = get_class($model);
 
-        $instance = new static("Call to undefined relationship [{$relation}] on model [{$class}].");
+        $instance = new static(
+            $type === null ?
+                "Call to undefined relationship [{$relation}] on model [{$class}]." :
+                "Call to undefined relationship [{$relation}] on model [{$class}] of type [{$type}].",
+        );
 
         $instance->model = $class;
         $instance->relation = $relation;

tests/Database/DatabaseEloquentBuilderTest.php

@@ -906,6 +906,35 @@ public function testPostgresOperatorsWhere()
         $this->assertEquals($result, $builder);
     }
 
+    public function testWhereBelongsTo()
+    {
+        $related = new EloquentBuilderTestWhereBelongsToStub([
+            'id' => 1,
+            'parent_id' => 2,
+        ]);
+
+        $parent = new EloquentBuilderTestWhereBelongsToStub([
+            'id' => 2,
+            'parent_id' => 1,
+        ]);
+
+        $builder = $this->getBuilder();
+        $builder->shouldReceive('from')->with('eloquent_builder_test_where_belongs_to_stubs');
+        $builder->setModel($related);
+        $builder->getQuery()->shouldReceive('where')->once()->with('parent_id', '=', 2, 'and');
+
+        $result = $builder->whereBelongsTo($parent);
+        $this->assertEquals($result, $builder);
+
+        $builder = $this->getBuilder();
+        $builder->shouldReceive('from')->with('eloquent_builder_test_where_belongs_to_stubs');
+        $builder->setModel($related);
+        $builder->getQuery()->shouldReceive('where')->once()->with('parent_id', '=', 2, 'and');
+
+        $result = $builder->whereBelongsTo($parent, 'parent');
+        $this->assertEquals($result, $builder);
+    }
+
     public function testDeleteOverride()
     {
         $builder = $this->getBuilder();
@@ -1948,3 +1977,21 @@ class EloquentBuilderTestStubStringPrimaryKey extends Model
 
     protected $keyType = 'string';
 }
+
+class EloquentBuilderTestWhereBelongsToStub extends Model
+{
+    protected $fillable = [
+        'id',
+        'parent_id',
+    ];
+
+    public function eloquentBuilderTestWhereBelongsToStub()
+    {
+        return $this->belongsTo(self::class, 'parent_id', 'id', 'parent');
+    }
+
+    public function parent()
+    {
+        return $this->belongsTo(self::class, 'parent_id', 'id', 'parent');
+    }
+}