[Bug]: Investigate and apply Permit token decimal value to Spending Cap and Message values

[digiwand]

Describe the bug

When we adopted fetchErc20Decimals for Permit Simulation, we enforced a default of 18 token decimals to be used when no token decimals are found in the details. fetchErc30Decimals is the same method used in ui/pages/confirmations/components/simulation-details/useBalanceChanges.test.ts which is why we adopted it.

Now, we can observe that the value no longer matches the value from previous confirmation versions.

Previously, clicking on test-dapp > Permit would display 3,000. Now, it displays 0 < 0.000001.

We also did not apply fetchErc20Decimals to the "Value" in the Message section which we can see the inconsistency of.

The question is, do we want to default to 18 decimals if no token decimals were found from the details?

If so:

• apply fetchErc20Decimals to Message > token values

Else:

• revert fetchErc20Decimals usage in permit-simulation or update fetchErc20Decimals default decimal value

Investigation Lead

@dbrans:

18 is the common convention for ERC20 tokens, largely due to OpenZeppelin's widely-used implementation. Vitalik proposed making it a required standard, though it didn’t gain momentum. EIP-1046 also suggests 18 as the default if decimals() isn’t implemented.

That said, some platforms, like Etherscan and certain wallets, default to zero when decimals() isn't defined, so there's a lot of inconsistency out there.

Expected behavior

No response

Screenshots/Recordings

Notice that Simulation > Spending Cap value does not match Message > Value

Steps to reproduce

1. Go to test-dapp
2. Click Permit button
3. Observe Spending Cap and Message > Value

Error messages or log output

No response

Detection stage

On the development branch

Version

12.2.2

Build type

None

Browser

Chrome

Operating system

MacOS

Hardware wallet

No response

Additional context

No response

Severity

No response

[bschorchit]

As discussed in the DSU, we can adopt the 18 decimals as the fallback and add metrics to capture when we fail to fetch decimals.
For metrics, we can re-use this event that we created for simulations:

event: Incomplete Asset Displayed

properties:
token_decimals_available: false
asset_address: < token address >
asset_type: erc20
chain_id: < chain id >
location: confirmation