Minor fixes described in changeset

.changeset/olive-pots-brush.md

@@ -0,0 +1,5 @@
+---
+'@chainlink/functions-toolkit': patch
+---
+
+Support `0x` in decodeResult, fixed simulator shutdown when error is encountered, added explicitly supported versions to README

README.md

@@ -6,6 +6,10 @@ Up-to-date documentation on Chainlink Functions can be found [here](https://docs
 
 > :warning: Chainlink Functions requires signing a terms of service agreement before creating a billing subscription. See this [getting started](https://docs.chain.link/chainlink-functions/getting-started) section in the docs.
 
+# Prerequisites
+
+Install Node.js version `18.18.0` or higher _and_ Deno version `1.36.0` or higher.
+
 # How to use this package
 
 The following classes expose functionality one would expect from their name.
@@ -23,6 +27,7 @@ The `SubscriptionManager` class is used to manage the Chainlink billing [subscri
 
 The typical subscriptions-related operations are
 
+- [Prerequisites](#prerequisites)
 - [How to use this package](#how-to-use-this-package)
   - [Functions Billing Subscription Management](#functions-billing-subscription-management)
     - [Subscription Initialization](#subscription-initialization)

src/decodeResult.ts

@@ -6,7 +6,7 @@ export const decodeResult = (
   resultHexstring: string,
   expectedReturnType: ReturnType,
 ): DecodedResult => {
-  if (!isValidHexadecimal(resultHexstring)) {
+  if (!isValidHexadecimal(resultHexstring) && resultHexstring.slice(0, 2) !== '0x') {
     throw Error(`'${resultHexstring}' is not a valid hexadecimal string`)
   }
   expectedReturnType = expectedReturnType.toLowerCase() as ReturnType
@@ -29,6 +29,9 @@ export const decodeResult = (
           `'${resultHexstring}' has '${resultHexBits}' bits which is too large for uint256`,
         )
       }
+      if (resultHexstring === '0x') {
+        return BigInt(0)
+      }
       decodedOutput = BigInt('0x' + resultHexstring.slice(2).slice(-64))
       break
     case ReturnType.int256:
@@ -37,9 +40,15 @@ export const decodeResult = (
           `'${resultHexstring}' has '${resultHexBits}' bits which is too large for int256`,
         )
       }
+      if (resultHexstring === '0x') {
+        return BigInt(0)
+      }
       decodedOutput = signedInt256toBigInt('0x' + resultHexstring.slice(2).slice(-64))
       break
     case ReturnType.string:
+      if (resultHexstring === '0x') {
+        return ''
+      }
       decodedOutput = Buffer.from(resultHexstring.slice(2), 'hex').toString()
       break
     case ReturnType.bytes:

src/simulateScript/deno-sandbox/sandbox.ts

@@ -452,8 +452,6 @@ try {
   }) as () => Promise<unknown>
   const result = await userScript()
 
-  __2___.close()
-
   if (!(result instanceof ArrayBuffer) && !(result instanceof Uint8Array)) {
     throw Error('returned value not an ArrayBuffer or Uint8Array')
   }
@@ -495,4 +493,6 @@ try {
         },
       }),
   )
+} finally {
+  __2___.close()
 }

test/unit/decode_result.test.ts

@@ -2,6 +2,24 @@ import { decodeResult, ReturnType } from '../../src/index'
 
 describe('decodeResult', () => {
   it.each([
+    {
+      result: '0x',
+      expectedDataType: ReturnType.string,
+      decodedResult: '',
+      label: 'decodes empty string',
+    },
+    {
+      result: '0x',
+      expectedDataType: ReturnType.uint256,
+      decodedResult: BigInt(0),
+      label: 'decodes empty uint256',
+    },
+    {
+      result: '0x',
+      expectedDataType: ReturnType.int256,
+      decodedResult: BigInt(0),
+      label: 'decodes empty int256',
+    },
     {
       result: '0x48656c6c6f2c20576f726c6421',
       expectedDataType: ReturnType.string,