fix: prevent race condition for swap state

[just-toby]

Description

This bug happens when the ConfirmSwapModal is dismissed before the swapCallback promise resolves.

When the bug happens, the state is set like this:

1. user proceeds normally and opens the ConfirmSwapModal -> showConfirm is true (set on L783)
2. handleSwap is called and triggers the swapCallback (L426). showConfirm is still true at this point
3. handleConfirmDismiss is called and showConfirm is set to false
4. swapCallback resolves and sets showConfirm to an outdated value (L428) which re-opens the modal

Test plan

Reproducing the error

1. see the test results for the swap/errors.test.ts test suite - it's flaky because this race condition causes the modal to stay visible when it shouldn't

QA (ie manual testing)

• this change totally fixes flakiness in certain swap e2e tests (tested in other branches)
• manually verified that the ConfirmSwapModal still works in the new permit2 flow with these changes

Automated testing

• Unit test N/A
• Integration/E2E test (existing test flakiness in other PRs is fixed by this change)

[vercel]

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Name	Status	Preview	Updated (UTC)
interface	✅ Ready (Inspect)	Visit Preview	May 22, 2023 10:20pm
interface-node18	✅ Ready (Inspect)	Visit Preview	May 22, 2023 10:20pm

[codecov]

Codecov Report

Patch coverage: 80.00% and project coverage change: -0.13 ⚠️

Comparison is base (f3a80c6) 60.18% compared to head (9e37cb7) 60.05%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6624      +/-   ##
==========================================
- Coverage   60.18%   60.05%   -0.13%     
==========================================
  Files         719      719              
  Lines       21143    21143              
  Branches     6974     6974              
==========================================
- Hits        12724    12697      -27     
- Misses       8342     8369      +27     
  Partials       77       77              

Flag	Coverage Δ
e2e-tests	60.49% <80.00%> (-0.14%)	⬇️
unit-tests	21.11% <0.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/pages/Swap/index.tsx	89.62% <80.00%> (ø)

... and 17 files with indirect coverage changes

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[cypress]

1 flaky tests on run #11211 ↗︎

0

69

8

0

1

Details:

fix: prevent race condition for swap state
Project: Uniswap Interface	Commit: 9e37cb7a29
Status: Passed	Duration: 06:05 💡
Started: May 22, 2023 10:28 PM	Ended: May 22, 2023 10:34 PM

  cypress/e2e/swap/swap.test.ts • 1 flaky test • e2e

View Output Video

Test		Artifacts
Swap > Swap on main page > swaps ETH for USDC		Output Screenshots Video

_{This comment has been generated by cypress-bot as a result of this project's GitHub integration settings.}

[tinaszheng]

nice fix!