Merge pull request #12 from swaggest/skip_if_isset

option to skip overwriting value if it is set

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 $isURIFragmentId
@@ -143,6 +148,9 @@ class JsonPointer
                 }
             }
         }
+        if ($ref !== null && $flags & self::SKIP_IF_ISSET) {
+            return;
+        }
         $ref = $value;
     }
 

tests/src/JsonPointerTest.php

@@ -17,6 +17,15 @@ class JsonPointerTest extends \PHPUnit_Framework_TestCase
         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 {