[9.x] Address Dynamic Relation Resolver inconsiency issue with extend…

…ed Models (#45122)

* laravel/framework#44741 - Address Dynamic Relation Resolver inconsistency issue with extended Models

* style fixes

Eloquent/Concerns/HasAttributes.php

@@ -541,7 +541,7 @@ public function isRelation($key)
         }
 
         return method_exists($this, $key) ||
-            (static::$relationResolvers[get_class($this)][$key] ?? null);
+               $this->relationResolver(static::class, $key);
     }
 
     /**

Eloquent/Concerns/HasRelationships.php

@@ -54,6 +54,26 @@ trait HasRelationships
      */
     protected static $relationResolvers = [];
 
+    /**
+     * Get the dynamic relation resolver if defined or inherited, or return null.
+     *
+     * @param  string  $class
+     * @param  string  $key
+     * @return mixed
+     */
+    public function relationResolver($class, $key)
+    {
+        if ($resolver = static::$relationResolvers[$class][$key] ?? null) {
+            return $resolver;
+        }
+
+        if ($parent = get_parent_class($class)) {
+            return $this->relationResolver($parent, $key);
+        }
+
+        return null;
+    }
+
     /**
      * Define a dynamic relation resolver.
      *

Eloquent/Model.php

@@ -2314,7 +2314,7 @@ public function __call($method, $parameters)
             return $this->$method(...$parameters);
         }
 
-        if ($resolver = (static::$relationResolvers[get_class($this)][$method] ?? null)) {
+        if ($resolver = ($this->relationResolver(static::class, $method))) {
             return $resolver($this);
         }