fix(#7044): toWei trim strings with more than 20 decimal places

Author: gordon-to

CHANGELOG.md

@@ -2480,6 +2480,7 @@ If there are any bugs, improvements, optimizations or any new feature proposal f
 
 #### web3-utils
 
+- Fixed `toWei` to avoid returning wrong value when more than 20 decimals passed as string (#7044)
 
 ### Fixed
 

packages/web3-utils/src/converters.ts

@@ -558,21 +558,22 @@ export const toWei = (number: Numbers, unit: EtherUnits): string => {
 	if (!denomination) {
 		throw new InvalidUnitError(unit);
 	}
-	let parsedNumber = number;
-	if (typeof parsedNumber === 'number'){
-		if (parsedNumber  < 1e-15){
+	let parsedNumber: string;
+	if (typeof number === 'number'){
+		if (number  < 1e-15){
 			console.warn(PrecisionLossWarning)
 		}
-		if (parsedNumber > 1e+20) {
+		if (number > 1e+20) {
 			console.warn(PrecisionLossWarning)
 
-			parsedNumber =  BigInt(parsedNumber);
+			parsedNumber =  BigInt(number).toLocaleString('fullwide');
 		} else {
 			// in case there is a decimal point, we need to convert it to string
-			parsedNumber = parsedNumber.toLocaleString('fullwide', {useGrouping: false, maximumFractionDigits: 20})
-		}
+			parsedNumber = number.toLocaleString('fullwide', {useGrouping: false, maximumFractionDigits: 20})
+        }
+
 	}
-	
+
 	// if value is decimal e.g. 24.56 extract `integer` and `fraction` part
 	// to avoid `fraction` to be null use `concat` with empty string
 	const [integer, fraction] = String(
@@ -581,10 +582,17 @@ export const toWei = (number: Numbers, unit: EtherUnits): string => {
 		.split('.')
 		.concat('');
 
+    // if the number of decimal places is over 20 we need to trim the extra decimal places before multiplying by
+    // the denomination to avoid returning an invalid result
+    let trimmedFraction = fraction
+    if (fraction.length >= 20) {
+        console.warn(PrecisionLossWarning)
+        trimmedFraction = fraction.substring(0,20)
+    }
+
 	// join the value removing `.` from
 	// 24.56 -> 2456
-	
-	const value = BigInt(`${integer}${fraction}`);
+	const value = BigInt(`${integer}${trimmedFraction}`);
 
 	// multiply value with denomination
 	// 2456 * 1000000 -> 2456000000