[12.x] mergeIfMissing allows merging with nested arrays (#52242)

* feat: mergeIfMissing allows merging with nested arrays

* Fix failing tests

* Fix styling

Author: KIKOmanasijev

src/Illuminate/Http/Request.php

@@ -349,9 +349,13 @@ public function userAgent()
      */
     public function merge(array $input)
     {
-        $this->getInputSource()->add($input);
-
-        return $this;
+        return tap($this, function (Request $request) use ($input) {
+            $request->getInputSource()
+                    ->replace(collect($input)->reduce(
+                        fn ($requestInput, $value, $key) => data_set($requestInput, $key, $value),
+                        $this->getInputSource()->all()
+                    ));
+        });
     }
 
     /**
@@ -547,8 +551,8 @@ public function hasSession(bool $skipIfUninitialized = false): bool
     public function getSession(): SessionInterface
     {
         return $this->hasSession()
-                    ? $this->session
-                    : throw new SessionNotFoundException;
+            ? $this->session
+            : throw new SessionNotFoundException;
     }
 
     /**

tests/Http/HttpRequestTest.php

@@ -983,6 +983,16 @@ public function testMergeIfMissingMethod()
         $request->mergeIfMissing($merge);
         $this->assertSame('Taylor', $request->input('name'));
         $this->assertSame(1, $request->input('boolean_setting'));
+
+        $request = Request::create('/', 'GET', ['user' => ['first_name' => 'Taylor', 'email' => 'taylor@laravel.com']]);
+        $merge = ['user.last_name' => 'Otwell'];
+        $request->mergeIfMissing($merge);
+        $this->assertSame('Otwell', $request->input('user.last_name'));
+
+        $request = Request::create('/', 'GET', ['user' => ['first_name' => 'Taylor', 'email' => 'taylor@laravel.com']]);
+        $merge = ['user.first_name' => 'John'];
+        $request->mergeIfMissing($merge);
+        $this->assertSame('Taylor', $request->input('user.first_name'));
     }
 
     public function testReplaceMethod()