Description

Due to slight difference in parsing of the ENABLE_MV3 environment variable, there is actually currently no value that will consistently disable MV3 (since !!'false' === true while !!'' === false).

This fixes this by:

• Using the exact same syntax to parse the ENABLE_MV3 environment variable consistently
• Refactor notifications test to skip MV3-specific tests under MV2, instead of marking them as passing without running them.
• Changing occurrence of process.env.ENABLE_MV3 in runtime to library function isManifestV3.

After this PR is merged:

• Setting ENABLE_MV3=true or leaving it unset will enable MV3
• Setting it to any other value disables it

This is in line with how it is interpreted in other parts of the stack.

Related issues

Fixes:

Manual testing steps

1. Go to this page...

Screenshots/Recordings

Before

After

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.