feat: mms-1876 swap pre populated

[GustavoRSSilva]

Description

Set a default token populated when going to the swap page

Related issues

Fixes:

Manual testing steps

1. Go to the swap page
2. Check token populated

Screenshots/Recordings

Before

After

Screen.Recording.2025-03-12.at.11.44.16.mov

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Extension Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

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.

[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.

[metamaskbot]

Builds ready [8c6052c]

• builds: chrome, firefox
• builds (flask): chrome, firefox
• builds (MMI): chrome
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5, 6, 7, 8
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
  • ui: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
  • content-script: 0
  • offscreen: 0

Page Load Metrics (2031 ± 149 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	1663	2600	1991	247	119
		domContentLoaded	1635	2403	1876	175	84
		load	1664	2892	2031	311	149
		domInteractive	25	73	36	13	6
		backgroundConnect	11	594	150	165	79
		firstReactRender	15	153	51	39	19
		getState	6	410	72	104	50
		initialActions	0	1	0	0	0
		loadScripts	1204	1823	1428	129	62
		setupStore	8	189	35	49	23
		uiStartup	1847	5410	2696	961	461

Bundle size diffs [🚨 Warning! Bundle size has increased!]

• background: 0 Bytes (0.00%)
• ui: 170 Bytes (0.00%)
• common: 2.27 KiB (0.02%)

[micaelae]

Can you add a condition here to skip pre-populating the toToken if the default token === fromToken?

Repro steps:

• From homepage, go to asset details page for the default token (i.e, USDC on ethereum)
• Click Swap from there
• See that the Swap page has USDC -> USDC filled in, which is an invalid route

[GustavoRSSilva]

updating it.