Make the updateOrCreate methods in relations use firstOrCreate behind the scenes

Related to laravel#48160, laravel#48192

Author: mpyw

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

@@ -672,17 +672,13 @@ public function createOrFirst(array $attributes = [], array $values = [], array
      */
     public function updateOrCreate(array $attributes, array $values = [], array $joining = [], $touch = true)
     {
-        if (is_null($instance = (clone $this)->where($attributes)->first())) {
-            if (is_null($instance = $this->related->where($attributes)->first())) {
-                return $this->create(array_merge($attributes, $values), $joining, $touch);
-            } else {
-                $this->attach($instance, $joining, $touch);
-            }
-        }
+        $instance = $this->firstOrCreate($attributes, $values, $joining, $touch);
 
-        $instance->fill($values);
+        if (! $instance->wasRecentlyCreated) {
+            $instance->fill($values);
 
-        $instance->save(['touch' => false]);
+            $instance->save(['touch' => false]);
+        }
 
         return $instance;
     }

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

@@ -271,11 +271,11 @@ public function firstOrNew(array $attributes)
      */
     public function updateOrCreate(array $attributes, array $values = [])
     {
-        $instance = $this->firstOrNew($attributes);
-
-        $instance->fill($values)->save();
-
-        return $instance;
+        return tap($this->firstOrCreate($attributes, $values), function ($instance) use ($values) {
+            if (! $instance->wasRecentlyCreated) {
+                $instance->fill($values)->save();
+            }
+        });
     }
 
     /**

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

@@ -267,10 +267,10 @@ public function createOrFirst(array $attributes = [], array $values = [])
      */
     public function updateOrCreate(array $attributes, array $values = [])
     {
-        return tap($this->firstOrNew($attributes), function ($instance) use ($values) {
-            $instance->fill($values);
-
-            $instance->save();
+        return tap($this->firstOrCreate($attributes, $values), function ($instance) use ($values) {
+            if (! $instance->wasRecentlyCreated) {
+                $instance->fill($values)->save();
+            }
         });
     }