Description

Currently, Extension can only process transactions for the active / globally selected network. This makes it not possible to facilitate multichain interactions without constantly rotating the active network or some other workaround that would hurt user experience. We want to keep Metamask competitive by making our multichain experience as seamless and frictionless as possible. This PR introduces an updated version of the TransactionController that is capable of handling transactions across multiple network clients concurrently which lays the groundwork for future multichain changes.

• Bumps @metamask/transaction-controller to ^23.0.0
• Adds TRANSACTION_MULTICHAIN environment variable
  • when set, enables the TransactionController to submit, process, and track transactions concurrently on mutiple networks
  • defaults off

NOTE: This PR does not introduce a CI pipeline for building and testing with TRANSACTION_MULTICHAIN enabled because the SwapController still needs to be updated to be compatible. This feature flag defaults off and does not change the current user facing TransactionController behavior, so current testing pipelines are sufficient.

Related issues

Fixes: https://github.com/MetaMask/MetaMask-planning/issues/1990

Manual testing steps

Testing the single globally selected transaction flow

There should be no user facing difference in behavior.

Testing the multichain transaction flow

1. Make a build with TRANSACTION_MULTICHAIN set to 1
2. Switch to local testnet network
3. Send a transaction
4. Quickly, before the transaction is marked confirmed, switch the globally selected network to a network on a different chain
5. Wait a few moments
6. Turn off the local testnet so that Metamask cannot connect to it anymore
7. Switch back to the testnet network
8. The transaction should be confirmed

This demonstrates that the TransactionController was polling the local testnet network for transaction updates while it was not the active / globally selected network and was able to confirm the transaction onchain (as opposed to it confirming the transaction right as it became the active / globally selected network again since Metamask wouldn't be able to reach the local testnet anymore)

Screenshots/Recordings

Before

Notice that the transaction was not confirmed when we switched to mainnet and that when we switched back to localhost that it confirmed instantly when we turned ganache back on, implying that the TransactionController is only polling for the currently active network.

After (with TRANSACTION_MULTICHAIN flag enabled)

Notice that the local testnet transaction was not confirmed before we switched to mainnet, but was confirmed by the time we switched back to it despite us being on mainnet and turning off ganache, implying that the TransactionController was polling for the local testnet transaction while mainnet was the globally selected network.

Pre-merge author checklist

• I’ve followed MetaMask Coding Standards.
• I've clearly explained what problem this PR is solving and how it is solved.
• I've linked related issues
• I've included manual testing steps
• I've included screenshots/recordings if applicable
• 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.
• I’ve properly set the pull request status:
  • In case it's not yet "ready for review", I've set it to "draft".
  • In case it's "ready for review", I've changed it from "draft" to "non-draft".

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.