GeezerVison

This PR revives #3930 as per the discussion at #4198 (comment). This PR aims to accomplish the same goals as #3930, but is updated based on changes that have happened in the codebase since. The original PR description follows.

Although we already clear environment variables that are set during unit tests, that does not affect the behaviour of core.exportVariable which additionally sets environment variables for subsequent steps in a workflow. If the unit tests are run in CI, then core.exportVariable sets environment variables for subsequent steps in the workflow job which can interfere with them.

This PR improves the situation by introducing a wrapper around core.exportVariable which does not call core.exportVariable when NODE_ENV is test (which is set automatically by ava).

The main change compared to the previous PR is that we now have ReadOnlyEnv and Env and it makes sense to integrate the logic of our exportVariable wrapper with those.

At first glance, a potential concern with using the export method of the Env class is that, if NODE_ENV is test, it only stores the environment variable in the Env instance. Other functions which may depend on the environment variable, but still use process.env to access it, do not see the value. However, all of the unit tests pass, and so we can rule out that this is an issue affecting the tests.

Outside of unit tests, where NODE_ENV is not expected to be set to test, the implementation calls core.exportVariable as well, which does set the environment variable for the process.

Risk assessment

For internal use only. Please select the risk level of this change:

• Low risk: Changes are fully under feature flags, or have been fully tested and validated in pre-production environments and are highly observable, or are documentation or test only.

Which use cases does this change impact?

Environments:

• Testing/None - This change does not impact any CodeQL workflows in production.

How did/will you validate this change?

• Unit tests - I am depending on unit test coverage (i.e. tests in .test.ts files).
• End-to-end tests - I am depending on PR checks (i.e. tests in pr-checks).

If something goes wrong after this change is released, what are the mitigation and rollback strategies?

• Rollback - Change can only be disabled by rolling back the release or releasing a new version with a fix.
• Development/testing only - This change cannot cause any failures in production.

How will you know if something goes wrong after this change is released?

• Telemetry - I rely on existing telemetry or have made changes to the telemetry.
  • Dashboards - I will watch relevant dashboards for issues after the release. Consider whether this requires this change to be released at a particular time rather than as part of a regular release.
  • Alerts - New or existing monitors will trip if something goes wrong with this change.

Are there any special considerations for merging or releasing this change?

• No special considerations - This change can be merged at any time.

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Consider adding a changelog entry for this change.
• Confirm the readme and docs have been updated if necessary.