From c9719f6bc8ee5ca28e2091db0cf530d18af2460f Mon Sep 17 00:00:00 2001
From: vpoturaev <viacheslav.poturaev@lazada.com>
Date: Sat, 28 Apr 2018 11:37:47 +0700
Subject: [PATCH] option to skip overwriting value if it is set

---
 src/JsonPointer.php           | 8 ++++++++
 tests/src/JsonPointerTest.php | 9 +++++++++
 2 files changed, 17 insertions(+)

diff --git a/src/JsonPointer.php b/src/JsonPointer.php
index 6ba10e7..1413cb3 100644
--- a/src/JsonPointer.php
+++ b/src/JsonPointer.php
@@ -15,6 +15,11 @@ class JsonPointer
      */
     const STRICT_MODE = 2;
 
+    /**
+     * Skip action if holder already has a non-null value at path
+     */
+    const SKIP_IF_ISSET = 4;
+
     /**
      * @param string $key
      * @param bool $isURIFragmentId
@@ -143,6 +148,9 @@ public static function add(&$holder, $pathItems, $value, $flags = self::RECURSIV
                 }
             }
         }
+        if ($ref !== null && $flags & self::SKIP_IF_ISSET) {
+            return;
+        }
         $ref = $value;
     }
 
diff --git a/tests/src/JsonPointerTest.php b/tests/src/JsonPointerTest.php
index 45d8a9b..9658bfd 100644
--- a/tests/src/JsonPointerTest.php
+++ b/tests/src/JsonPointerTest.php
@@ -17,6 +17,15 @@ public function testProcess()
         JsonPointer::add($json, ['l1','l2','l3'], 'hello!');
         $this->assertSame('{"l1":{"l2":{"l3":"hello!"}}}', json_encode($json));
 
+        JsonPointer::add($json, ['l1', 'l2', 'l3'], 'hello again!', JsonPointer::SKIP_IF_ISSET);
+        $this->assertSame('{"l1":{"l2":{"l3":"hello!"}}}', json_encode($json));
+
+        JsonPointer::add($json, ['l1', 'l2', 'l3'], 'hello again!');
+        $this->assertSame('{"l1":{"l2":{"l3":"hello again!"}}}', json_encode($json));
+
+        JsonPointer::add($json, ['l1', 'l2', 'l3'], 'hello!');
+        $this->assertSame('{"l1":{"l2":{"l3":"hello!"}}}', json_encode($json));
+
         $this->assertSame('{"l3":"hello!"}', json_encode(JsonPointer::get($json, JsonPointer::splitPath('/l1/l2'))));
 
         try {