[8.x] Add support for disallowing class morphs

src/Illuminate/Database/ClassMorphViolationException.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace Illuminate\Database;
+
+use RuntimeException;
+
+class ClassMorphViolationException extends RuntimeException
+{
+    /**
+     * The name of the affected Eloquent model.
+     *
+     * @var string
+     */
+    public $model;
+
+    /**
+     * Create a new exception instance.
+     *
+     * @param  object  $model
+     */
+    public function __construct($model)
+    {
+        $class = get_class($model);
+
+        parent::__construct("No morph map defined for model [{$class}].");
+
+        $this->model = $class;
+    }
+}

src/Illuminate/Database/Eloquent/Concerns/HasRelationships.php

@@ -3,6 +3,7 @@
 namespace Illuminate\Database\Eloquent\Concerns;
 
 use Closure;
+use Illuminate\Database\ClassMorphViolationException;
 use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Collection;
 use Illuminate\Database\Eloquent\Model;
@@ -731,6 +732,10 @@ public function getMorphClass()
             return array_search(static::class, $morphMap, true);
         }
 
+        if (Relation::requiresMorphMap()) {
+            throw new ClassMorphViolationException($this);
+        }
+
         return static::class;
     }
 

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

@@ -57,6 +57,13 @@ abstract class Relation
      */
     public static $morphMap = [];
 
+    /**
+     * Prevents morph relationships without a morph map.
+     *
+     * @var bool
+     */
+    protected static $requireMorphMap = false;
+
     /**
      * The count of self joins.
      *
@@ -376,6 +383,41 @@ protected function whereInMethod(Model $model, $key)
                         : 'whereIn';
     }
 
+    /**
+     * Prevent polymorphic relationships from being used without model mappings.
+     *
+     * @param  bool  $requireMorphMap
+     * @return void
+     */
+    public static function requireMorphMap($requireMorphMap = true)
+    {
+        static::$requireMorphMap = $requireMorphMap;
+    }
+
+    /**
+     * Determine if polymorphic relationships require explicit model mapping.
+     *
+     * @return bool
+     */
+    public static function requiresMorphMap()
+    {
+        return static::$requireMorphMap;
+    }
+
+    /**
+     * Define the morph map for polymorphic relations and require all morphed models to be explicitly mapped.
+     *
+     * @param  array|null  $map
+     * @param  bool  $merge
+     * @return array
+     */
+    public static function enforceMorphMap(array $map, $merge = true)
+    {
+        static::requireMorphMap();
+
+        return static::morphMap($map, $merge);
+    }
+
     /**
      * Set or get the morph map for polymorphic relations.
      *

tests/Integration/Database/EloquentStrictMorphsTest.php

@@ -0,0 +1,65 @@
+<?php
+
+namespace Illuminate\Tests\Integration\Database;
+
+use Illuminate\Database\ClassMorphViolationException;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\Relation;
+use Orchestra\Testbench\TestCase;
+
+class EloquentStrictMorphsTest extends TestCase
+{
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        Relation::requireMorphMap();
+    }
+
+    public function testStrictModeThrowsAnExceptionOnClassMap()
+    {
+        $this->expectException(ClassMorphViolationException::class);
+
+        $model = TestModel::make();
+
+        $model->getMorphClass();
+    }
+
+    public function testStrictModeDoesNotThrowExceptionWhenMorphMap()
+    {
+        $model = TestModel::make();
+
+        Relation::morphMap([
+            'test' => TestModel::class,
+        ]);
+
+        $morphName = $model->getMorphClass();
+        $this->assertEquals('test', $morphName);
+    }
+
+    public function testMapsCanBeEnforcedInOneMethod()
+    {
+        $model = TestModel::make();
+
+        Relation::requireMorphMap(false);
+
+        Relation::enforceMorphMap([
+            'test' => TestModel::class,
+        ]);
+
+        $morphName = $model->getMorphClass();
+        $this->assertEquals('test', $morphName);
+    }
+
+    protected function tearDown(): void
+    {
+        parent::tearDown();
+
+        Relation::morphMap([], false);
+        Relation::requireMorphMap(false);
+    }
+}
+
+class TestModel extends Model
+{
+}