From 627b54768293ec277f1adb997c888ec524f4174d Mon Sep 17 00:00:00 2001
From: Jb Aviat <jb@sqreen.io>
Date: Fri, 22 May 2020 14:19:14 +0200
Subject: [PATCH] Fix array conversion when size changes dynamically

---
 .../extension/mini_racer_extension.cc         |  9 ++-
 tests/test_array_growth.py                    | 80 +++++++++++++++++++
 2 files changed, 86 insertions(+), 3 deletions(-)
 create mode 100644 tests/test_array_growth.py

diff --git a/py_mini_racer/extension/mini_racer_extension.cc b/py_mini_racer/extension/mini_racer_extension.cc
index da4a6049..52b064b4 100644
--- a/py_mini_racer/extension/mini_racer_extension.cc
+++ b/py_mini_racer/extension/mini_racer_extension.cc
@@ -447,20 +447,23 @@ static BinaryValue *convert_v8_to_binary(Isolate * isolate,
 
     else if (value->IsArray()) {
         Local<Array> arr = Local<Array>::Cast(value);
-        size_t len = arr->Length();
+        uint32_t len = arr->Length();
+
         BinaryValue **ary = xalloc(ary, sizeof(*ary) * len);
 
         res->type = type_array;
         res->array_val = ary;
+        res->len = (size_t) len;
 
-        for(uint32_t i = 0; i < arr->Length(); i++) {
+        for(uint32_t i = 0; i < len; i++) {
             Local<Value> element = arr->Get(context, i).ToLocalChecked();
             BinaryValue *bin_value = convert_v8_to_binary(isolate, context, element);
             if (bin_value == NULL) {
+                // adjust final array length
+                res->len = (size_t) i;
                 goto err;
             }
             ary[i] = bin_value;
-            res->len++;
         }
     }
 
diff --git a/tests/test_array_growth.py b/tests/test_array_growth.py
new file mode 100644
index 00000000..8605e0ae
--- /dev/null
+++ b/tests/test_array_growth.py
@@ -0,0 +1,80 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+""" Growing and reducing arrays """
+
+import unittest
+import json
+import time
+
+from datetime import datetime
+
+from py_mini_racer import py_mini_racer
+
+
+class Test(unittest.TestCase):
+    """ Test basic types """
+
+
+    def setUp(self):
+
+        self.mr = py_mini_racer.MiniRacer()
+
+    def test_growing_array(self):
+
+        js = """
+    var global_array = [
+        {
+            get first() {
+                for(var i=0; i<100; i++) {
+                    global_array.push(0x41);
+                }
+            }
+        }
+    ];
+
+    // when accessed, the first element will make the array grow by 100 items.
+    global_array;
+    """
+
+        res = self.mr.eval(js)
+        # Initial array size was 100
+        self.assertEqual(res, [{'first': None}])
+
+
+    def test_shrinking_array(self):
+            js = """
+    var global_array = [
+        {
+            get first() {
+                for(var i=0; i<100; i++) {
+                    global_array.pop();
+                }
+            }
+        }
+    ];
+
+    // build a 200 elements array
+    for(var i=0; i < 200; i++)
+        global_array.push(0x41);
+
+    // when the first item will be accessed, it should remove 100 items.
+
+    global_array;
+            """
+
+            # The final array should have:
+            #   The initial item
+            #   The next 100 items (value 0x41)
+            #   The last 100 items which have been removed when the initial key was accessed
+            array = [{'first': None}] + \
+                    [0x41] * 100      + \
+                    [None] * 100
+
+            res = self.mr.eval(js)
+            self.assertEqual(res, array)
+
+
+if __name__ == '__main__':
+    import sys
+    sys.exit(unittest.main())