feat: Add Multichain API to Flask

[jiexi]

Description

This branch adds support for the Multichain API to the Flask build of the Extension.

The existing API (via injected provider) should be completely unchanged.

(Very Briefly) What is the MetaMask Multichain API

• Concurrent connection to any number of chains (no network switching)
• Unified entry point for all chain ecosystems (EVM, BTC, Solana, Cosmos, Polkadot etc)
• Accessible (on extension for chromium based browsers) via externally_connectable. Not accessible via an injected global like window.ethereum

Key Documents/Standards

mip = MetaMask Improvement Proposal

• MIP-5 (Overview of the Multichain API)
  • CAIP-25 (new connection request API)
  • CAIP-27 (new request API, envelope with target scope/chainId included)
• MIP-6 (Overview of how the Multichain API’s EVM support diverges from the 1193 injected provider)

Manual testing steps

yarn start:flask

Then

(RECOMMENDED) Use the Multichain Test Dapp

• Video Demo for Interacting w/ Multichain Test Dapp

OR

Form requests manually

Pre-merge author checklist

• I’ve followed MetaMask 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.

[jiexi]

@metamaskbot update-policies

[metamaskbot]

Policies updated.
👀 Please review the diff for suspicious new powers.

🧠 Learn how: https://lavamoat.github.io/guides/policy-diff/#what-to-look-for-when-reviewing-a-policy-diff

[socket-security]

👍 Dependency issues cleared. Learn more about Socket for GitHub ↗︎

This PR previously contained dependency changes with security issues that have been resolved, removed, or ignored.

View full report↗︎

[shanejonas]

this PR needs the patches from here: https://github.com/MetaMask/metamask-extension/pull/27847/files#r1801195961

[jiexi]

REMINDER: check the original feature branch PR for unresolved comments

[jiexi]

TODO: Convert BARAD_DUR flag into flask feature flag

Done here #29003

[jiexi]

@metamaskbot update-policies

[metamaskbot]

Policies updated.
👀 Please review the diff for suspicious new powers.

🧠 Learn how: https://lavamoat.github.io/guides/policy-diff/#what-to-look-for-when-reviewing-a-policy-diff

[metamaskbot]

❌ Multichain API Spec Test Failed. View the report here.

[socket-security]

New, updated, and removed dependencies detected. Learn more about Socket for GitHub ↗︎

Package	New capabilities	Transitives	Size	Publisher
npm/@metamask/[email protected] 🔁 npm/@metamask/[email protected]	None	0	294 kB	metamaskbot
npm/@metamask/[email protected]	None	0	1.69 MB	metamaskbot
npm/@open-rpc/[email protected] 🔁 npm/@open-rpc/[email protected]	Transitive: environment, eval	+6	1.4 MB	belfordz

🚮 Removed packages: npm/[email protected]

View full report↗︎

[metamaskbot]

❌ Multichain API Spec Test Failed. View the report here.

[metamaskbot]

Builds ready [22957ef]

• 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
  • 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 (1531 ± 69 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	350	2087	1470	293	141
		domContentLoaded	1393	2037	1511	135	65
		load	1404	2087	1531	143	69
		domInteractive	23	70	40	19	9
		backgroundConnect	8	77	22	17	8
		firstReactRender	15	70	30	21	10
		getState	4	51	13	15	7
		initialActions	0	1	0	0	0
		loadScripts	984	1505	1094	108	52
		setupStore	6	62	13	14	7
		uiStartup	1584	2375	1745	166	80

Bundle size diffs [🚀 Bundle size reduced!]

• background: -703 Bytes (-0.01%)
• ui: 16 Bytes (0.00%)
• common: 327 Bytes (0.00%)

[metamaskbot]

❌ API Spec Test Failed. View the report here.

[metamaskbot]

❌ API Spec Test Failed. View the report here.