[Bug]: cannot send tokens with decimals > 20

[think-in-universe]

Describe the bug

Problem

When I'm trying to transfer $NEAR (also called WNEAR) in Aurora mainnet network, I cannot input the amount in the Send page in MetaMask. No matter what number I input, the value on the Send page will be 0. So I cannot transfer any $NEAR token in Aurora network with MetaMask.

• The address of $NEAR token on Aurora mainnet is: https://aurorascan.dev/address/0xC42C30aC6Cc15faC9bD938618BcaA1a1FaE8501d
• $NEAR is a ERC20 token, but its decimals is 24, which makes it special.

Analysis

The the issue is that when converting the value in the below function, the rate will become 0, and make the returned convertedValue to be 0 always.

metamask-extension/shared/modules/conversion.utils.js

Lines 117 to 120 in 3732c5f

	if (invertConversionRate) {
	rate = new BigNumber(1.0).div(conversionRate);
	}
	convertedValue = convertedValue.times(rate);

The root cause is, in LINE 118, conversionRate is 1e24 because $NEAR's decimals is 24, but the default DECIMAL_PLACES of BigNumber is 20, as stated here https://mikemcl.github.io/bignumber.js/#decimal-places

Default value: 20
The maximum number of decimal places of the results of operations involving division, i.e. division, square root and base conversion operations, and power operations with negative exponents.

As a result, any number smaller than 1e-20 will become 0. That's why any input for $NEAR amount will become 0.

A quick fix is to specify a large enough DECIMAL_PLACES in BigNumber.

BigNumber.config({ DECIMAL_PLACES: 32 })

Reference

• WNEAR token on Aurora mainnet: https://aurorascan.dev/address/0xC42C30aC6Cc15faC9bD938618BcaA1a1FaE8501d
• DECIMAL_PLACES setting in bignumber.js: https://mikemcl.github.io/bignumber.js/#decimal-places

Steps to reproduce

We can reproduce the issue on Aurora testnet:

1. Create a NEAR testnet account on: https://wallet.testnet.near.org/
2. Transfer some $NEAR from your NEAR account to Aurora account with Rainbow Bridge: https://testnet.rainbowbridge.app/ (you will need to connect to both NEAR and Aurora accounts, and then you can start the transfer)
3. Try to transfer your $NEAR on Aurora to another account in MetaMask

Error messages or log output

No

Version

10.12.4

Build type

No response

Browser

Chrome

Operating system

MacOS

Hardware wallet

No response

Additional context

Besides $NEAR, this should also happen to other tokens on Aurora with decimals = 24

[jatubio]

I have the same problem. Is it solved?

[dbale-altoros]

I also have the same problem when using metamask with this token
0xE39A5100B5B5b9985c5338B873eE2B10D5C36A7a on GOERLI
And also with this one
0x265C681aA55E8483e04788902e9190bd03a7f443 on MUMBAI

Is there any fix ?