Fix parsing of strings, fixes #3543

src/Composer/Json/JsonManipulator.php

@@ -31,7 +31,7 @@ class JsonManipulator
         if (!self::$RECURSE_BLOCKS) {
             self::$RECURSE_BLOCKS = '(?:[^{}]*|\{(?:[^{}]*|\{(?:[^{}]*|\{(?:[^{}]*|\{[^{}]*\})*\})*\})*\})*';
             self::$RECURSE_ARRAYS = '(?:[^\]]*|\[(?:[^\]]*|\[(?:[^\]]*|\[(?:[^\]]*|\[[^\]]*\])*\])*\])*\]|'.self::$RECURSE_BLOCKS.')*';
-            self::$JSON_STRING = '"(?:\\\\["bfnrt/\\\\]|\\\\u[a-fA-F0-9]{4}|[^\0-\x09\x0a-\x1f\\\\"])+"';
+            self::$JSON_STRING = '"(?:\\\\["bfnrt/\\\\]|\\\\u[a-fA-F0-9]{4}|[^\0-\x09\x0a-\x1f\\\\"])*"';
             self::$JSON_VALUE = '(?:[0-9.]+|null|true|false|'.self::$JSON_STRING.'|\['.self::$RECURSE_ARRAYS.'\]|\{'.self::$RECURSE_BLOCKS.'\})';
         }
 

tests/Composer/Test/Json/JsonManipulatorTest.php

@@ -73,6 +73,7 @@ class JsonManipulatorTest extends \PHPUnit_Framework_TestCase
             ),
             array(
                 '{
+    "empty": "",
     "require": {
         "foo": "bar"
     }
@@ -81,6 +82,7 @@ class JsonManipulatorTest extends \PHPUnit_Framework_TestCase
                 'vendor/baz',
                 'qux',
                 '{
+    "empty": "",
     "require": {
         "foo": "bar",
         "vendor/baz": "qux"