fix: Worker hangs when posting "undefined" as message (#8920)

This commit fixes hang in web workers occuring when sending
"undefined" as message value. It is a temporary band-aid
until proper structured close is implemented.

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/runtime/js/11_workers.js b/runtime/js/11_workers.js
index 57f420728..e943d66bc 100644
--- a/runtime/js/11_workers.js
+++ b/runtime/js/11_workers.js
@@ -47,6 +47,13 @@
   }
 
   function decodeMessage(dataIntArray) {
+    // Temporary solution until structured clone arrives in v8.
+    // Current clone is made by parsing json to byte array and from byte array back to json.
+    // In that case "undefined" transforms to empty byte array, but empty byte array does not transform back to undefined.
+    // Thats why this special is statement is needed.
+    if (dataIntArray.length == 0) {
+      return undefined;
+    }
     const dataJson = decoder.decode(dataIntArray);
     return JSON.parse(dataJson);
   }