StringStream is wrongly assuming that array items cannot be empty

When trying to deserialized a serialized array with an empty item, neon-js is throwing an error:

Reached the end of the stream!

I believe this should not happen, it should not be illegal to have empty items in a serialized array.

For example:

// We have a serialized array from a smart contract, for example: ['test','neon','']
serialized = '800200077075626c69736880040014f8af73dc ...'

// We try to deserialize it in neon-js:
deserialized = Neon.sc.StackItem.deserialize(serialized).value;
console.log(deserialized);

This will throw an error:

(node:25781) UnhandledPromiseRejectionWarning: Error: Reached the end of the stream!
    at StringStream.read (/usr/local/src/project/node_modules/@cityofzion/neon-js/dist/index.js:24755:19)
    at Function._deserialize (/usr/local/src/project/node_modules/@cityofzion/neon-js/dist/index.js:23029:33)
    at Function._deserialize (/usr/local/src/project/node_modules/@cityofzion/neon-js/dist/index.js:23014:42)
    at Function._deserialize (/usr/local/src/project/node_modules/@cityofzion/neon-js/dist/index.js:23014:42)
    at Function.deserialize (/usr/local/src/project/node_modules/@cityofzion/neon-js/dist/index.js:23005:21)
    at init (/usr/local/src/project/index.js:62:35)
    at Object.<anonymous> (/usr/local/src/project/index.js:71:1)
    at Module._compile (module.js:652:30)
    at Object.Module._extensions..js (module.js:663:10)
    at Module.load (module.js:565:32)
(node:25781) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:25781) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Proposed fix:

diff --git a/packages/neon-core/src/u/StringStream.ts b/packages/neon-core/src/u/StringStream.ts
index ebca4f2..f577213 100644
--- a/packages/neon-core/src/u/StringStream.ts
+++ b/packages/neon-core/src/u/StringStream.ts
@@ -51,9 +51,6 @@ export class StringStream {
    * ss.read(2); // "0203"
    */
   public read(bytes: number = 1): string {
-    if (this.isEmpty()) {
-      throw new Error("Reached the end of the stream!");
-    }
     const out = this.str.substr(this.pter, bytes * 2);
     this.pter += bytes * 2;
     return out;

[snowypowers]

v4.4.0 is released and includes this fix. Please verify it on your side.

[snowypowers]

I dug into this and found the reason why. When you place the zero at the end, the serialized output actually serialized it as a null, the OpCodes produced are 0000 which can be interpreted as:

00 (OpCode to indicate type ByteArray)
00 (OpCode to indicate length of bytes to read)

Essentially, the read(0) bytes off the stream is triggering the error because the stream is empty. The issue I have here is if this is intended. Are you intending to insert a null or actually insert the bytearray of length 1 with data 00. Because you used an int instead of a string there, the case is even more ambiguous.

If the null case is the correct way, we can amend read(0) to return null. Else, we should be amending the StackItem deserializer to prevent a read(0) and fill in some defaults.