From 4b18d48366432908126d3f808a0fa61e13b31ebf Mon Sep 17 00:00:00 2001
From: Dan J Miller <danjm.com@gmail.com>
Date: Fri, 3 Feb 2023 08:00:49 -0800
Subject: [PATCH] Ensure the advanced gas modal displays a zero priority fee if
 that is how it is set in the transaction (#17559)

Co-authored-by: Pedro Figueiredo <pedro.figueiredo@consensys.net>
---
 .../gasFeeInput/useMaxPriorityFeePerGasInput.js  | 16 ++++++++++------
 .../useMaxPriorityFeePerGasInput.test.js         | 11 +++++++++++
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/ui/hooks/gasFeeInput/useMaxPriorityFeePerGasInput.js b/ui/hooks/gasFeeInput/useMaxPriorityFeePerGasInput.js
index 478039ca1..da29cb676 100644
--- a/ui/hooks/gasFeeInput/useMaxPriorityFeePerGasInput.js
+++ b/ui/hooks/gasFeeInput/useMaxPriorityFeePerGasInput.js
@@ -7,6 +7,8 @@ import { isLegacyTransaction } from '../../helpers/utils/transactions.util';
 import { hexWEIToDecGWEI } from '../../../shared/lib/transactions-controller-utils';
 import { feeParamsAreCustom, getGasFeeEstimate } from './utils';
 
+const isNullOrUndefined = (value) => value === null || value === undefined;
+
 const getMaxPriorityFeePerGasFromTransaction = (
   transaction,
   gasFeeEstimates,
@@ -17,9 +19,8 @@ const getMaxPriorityFeePerGasFromTransaction = (
   }
   const { maxPriorityFeePerGas, maxFeePerGas, gasPrice } =
     transaction?.txParams || {};
-  return Number(
-    hexWEIToDecGWEI(maxPriorityFeePerGas || maxFeePerGas || gasPrice),
-  );
+  const feeInHexWei = maxPriorityFeePerGas || maxFeePerGas || gasPrice;
+  return feeInHexWei ? Number(hexWEIToDecGWEI(feeInHexWei)) : null;
 };
 
 /**
@@ -50,17 +51,20 @@ export function useMaxPriorityFeePerGasInput({
 
   const initialMaxPriorityFeePerGas = supportsEIP1559
     ? getMaxPriorityFeePerGasFromTransaction(transaction, gasFeeEstimates)
-    : 0;
+    : null;
 
   const [maxPriorityFeePerGas, setMaxPriorityFeePerGas] = useState(() => {
-    if (initialMaxPriorityFeePerGas && feeParamsAreCustom(transaction)) {
+    if (
+      !isNullOrUndefined(initialMaxPriorityFeePerGas) &&
+      feeParamsAreCustom(transaction)
+    ) {
       return initialMaxPriorityFeePerGas;
     }
     return null;
   });
 
   useEffect(() => {
-    if (supportsEIP1559 && initialMaxPriorityFeePerGas) {
+    if (supportsEIP1559 && !isNullOrUndefined(initialMaxPriorityFeePerGas)) {
       setMaxPriorityFeePerGas(initialMaxPriorityFeePerGas);
     }
   }, [initialMaxPriorityFeePerGas, setMaxPriorityFeePerGas, supportsEIP1559]);
diff --git a/ui/hooks/gasFeeInput/useMaxPriorityFeePerGasInput.test.js b/ui/hooks/gasFeeInput/useMaxPriorityFeePerGasInput.test.js
index ac79332ed..ce2afeb79 100644
--- a/ui/hooks/gasFeeInput/useMaxPriorityFeePerGasInput.test.js
+++ b/ui/hooks/gasFeeInput/useMaxPriorityFeePerGasInput.test.js
@@ -102,4 +102,15 @@ describe('useMaxPriorityFeePerGasInput', () => {
     });
     expect(result.current.maxPriorityFeePerGas).toBe(100);
   });
+
+  it('returns maxPriorityFeePerGas from transaction if it is 0', () => {
+    const { result } = renderUseMaxPriorityFeePerGasInputHook({
+      transaction: {
+        txParams: {
+          maxPriorityFeePerGas: '0x0',
+        },
+      },
+    });
+    expect(result.current.maxPriorityFeePerGas).toBe(0);
+  });
 });