Add Hex Check For User Input

[rduttshukla]

Development & PR Process

1. Follow MetaMask Mobile Coding Standards
2. Add release-xx label to identify the PR slated for a upcoming release (will be used in release discussion)
3. Add needs-dev-review label when work is completed
4. Add needs-qa label when dev review is completed
5. Add QA Passed label when QA has signed off

Description

Added hex check for user input under Send Flow, the lack of which was causing the app to crash due to the toWei method not supporting hex strings. The reason for writing this PR are as below

1. The app crashed when I accidentally pasted a wallet address into the amount text input
2. Simply writing 0x1 also crashes the app

Screenshots/Recordings

Here is the screen recording demonstrating the issue.

WhatsApp.Video.2023-02-02.at.23.25.06.mp4

Issue

The issue is that the isDecimal check returns true a string like '0x1' but the resulting hex string is incompatible with the toWei method. While we can change the isDecimal to return false for hex strings, the solution I preferred is checking the string in the onInputChange method instead.

While we should depend on the keyboardType prop set as numeric, but as seen in the screen recording, it did not work as expected. Moreover, the prop didn't prevent pasting of non-numeric data at my end.

[github-actions]

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

[rduttshukla]

I have read the CLA Document and I hereby sign the CLA

[legobeat]

@MetaMask/mobile-devs PTAL

[digiwand]

hey @rduttshukla, thanks for the catch and fix! LGTM

I think we can add a test for invalid inputs with or following this PR

[legobeat]

This functionality is already imported at least through ethers.
See app/components/UI/PaymentRequest/index.js for example.

[legobeat]

@digiwand looks like this may be an inconsistent update-merge - could you take a look and rebase if necessary?

[digiwand]

Nice catch @legobeat. agreed using the ethers module would be preferred here too

---

I used the GitHub UI to resolve the merge conflict. I checked out the PR and the code looks good to me still

[leotm]

@digiwand looks like we're still importing from ethjs-util after the merge
could you retry or add a commit importing/using ethers? should fix the CI lint error too

[leotm]

🧹 as an aside could also follow-up separately to update below to ethers 🧹

metamask-mobile/app/util/address/index.js

Lines 4 to 8 in fbbd7d5

	isHexString,
	addHexPrefix,
	isValidChecksumAddress,
	isHexPrefixed,
	} from 'ethereumjs-util';

[legobeat]

^ Dropping ethereumjs-util (deprecated) in favor of either ethers or @ethereumjs/util would be great I think