From 8d2d49ce0662452f8c73d9f1410b5a586fa3ee30 Mon Sep 17 00:00:00 2001
From: Nazar Hussain <nazarhussain@gmail.com>
Date: Thu, 27 Jan 2022 13:14:43 +0500
Subject: [PATCH] '0x' strings returned by contract are incorrectly interpreted
 as nulls (#4730)

* :bug: Fix decoding bug for the "0x" string

* :art: Update the validation check

* :art: Improve the condition to be more readable

* :memo: Update change log doc
---
 CHANGELOG.md                                        | 1 +
 packages/web3-eth-abi/src/index.js                  | 7 ++++++-
 packages/web3-eth-abi/types/tests/abi-coder-test.ts | 6 ++++++
 test/abi.decodeParameter.js                         | 3 +++
 4 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d2ec938d5d7..bac119c625f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -507,6 +507,7 @@ Released with 1.0.0-beta.37 code base.
 -  Updated README to include Webpack 5 create-react-app support instructions (#4173)
 -  Update the documentation for `methods.myMethod.estimateGas` (#4702)
 -  Fix typos in REVIEW.md and TESTING.md (#4691)
+-  Fix encoding for "0x" string values (#4512)
 
 
 ### Changed
diff --git a/packages/web3-eth-abi/src/index.js b/packages/web3-eth-abi/src/index.js
index 63728ac567c..8eaebdc35d2 100644
--- a/packages/web3-eth-abi/src/index.js
+++ b/packages/web3-eth-abi/src/index.js
@@ -362,7 +362,12 @@ ABICoder.prototype.decodeParametersWith = function (outputs, bytes, loose) {
 
     outputs.forEach(function (output, i) {
         var decodedValue = res[returnValue.__length__];
-        decodedValue = (decodedValue === '0x') ? null : decodedValue;
+
+        const isStringObject = typeof output === 'object' && output.type && output.type === 'string';
+        const isStringType = typeof output === 'string' && output === 'string';
+
+        // only convert `0x` to null if it's not string value
+        decodedValue = (decodedValue === '0x' && !isStringObject && !isStringType) ? null : decodedValue;
 
         returnValue[i] = decodedValue;
 
diff --git a/packages/web3-eth-abi/types/tests/abi-coder-test.ts b/packages/web3-eth-abi/types/tests/abi-coder-test.ts
index 0ed89e58c0a..677741041be 100644
--- a/packages/web3-eth-abi/types/tests/abi-coder-test.ts
+++ b/packages/web3-eth-abi/types/tests/abi-coder-test.ts
@@ -327,6 +327,12 @@ abiCoder.decodeParameter(
     0000000000000000000000004e`
 );
 
+// $ExpectType { [key: string]: any; }
+abiCoder.decodeParameter(
+    'string',
+    '0x000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000023078000000000000000000000000000000000000000000000000000000000000'
+);
+
 // $ExpectError
 abiCoder.decodeParameter('uint256', [345]);
 // $ExpectError
diff --git a/test/abi.decodeParameter.js b/test/abi.decodeParameter.js
index 6c09e2f2ed8..0e9c79cfa7b 100644
--- a/test/abi.decodeParameter.js
+++ b/test/abi.decodeParameter.js
@@ -635,6 +635,9 @@ describe('lib/solidity/coder', function () {
                         '0000000000000000000000000000000000000000000000000000000000000060' +
                         '0000000000000000000000000000000000000000000000000000000000000006' +
                         '737472696e670000000000000000000000000000000000000000000000000000'})
+
+        test( { types: ['string'], expected: ["0x"],
+                values: '0x000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000023078000000000000000000000000000000000000000000000000000000000000'})
     });
 });