Description

1. What is the reason for the change?
   When the user changed the payment token or when the effective balance dropped, the Perps order form was resetting the amount to max whenever the current amount was greater than the new max. That logic could also run when the user had intentionally set the amount to 0 or left it empty (e.g. initial value 10), and setAmount was forcing empty values to '0', which made it harder to preserve the intended initial amount.

2. What is the improvement/solution?

   • In the useEffect that reacts to balanceForMax / maxPossibleAmount / orderForm.amount: only reset the amount when it actually exceeds the new max. If currentAmount === 0, maxPossibleAmount === 0, or currentAmount < maxPossibleAmount, we return early and do not overwrite the form amount.
   • In setAmount, pass through the amount string as-is and remove the || '0' fallback so the form can keep an empty or user-chosen initial value (e.g. 10) without being forced to '0'.

Changelog

CHANGELOG entry: Fixed Perps order form so the amount is only reset when it exceeds the new max after changing payment token or balance, and no longer overwrites an initial or empty amount.

Related issues

Fixes:

Manual testing steps

Feature: Perps order form amount when balance or payment token changes

  Scenario: user has set amount to 10 and then changes payment token
    Given user is on the Perps order view with amount set to 10 (or another value below the new max)

    When user changes the payment token (or balance updates so max possible amount changes)
    Then the amount remains 10 and is not reset to max or to 0

Screenshots/Recordings

Before

No visible change

After

No visible change

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Mobile Coding Standards.
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• I've included tests if applicable
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Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.