Prevent merge of unsynchronized `yarn.lock` files

[MikeMcC399]

What would you like?

The develop branch should be protected against merging commits with unsynchronized yarn.lock files.

Running yarn on any commit in the develop branch, or destined for this branch, should not produce any differences in yarn.lock.

Why is this needed?

If commits with unsynchronized yarn.lock files are merged into the develop branch then follow-on PRs are forced into cleaning up the mismatch of their predecessor(s) leading to a confusing change history.

Other

Examples of PRs merged with unsynchronized yarn.lock files:

Renovate

See

• https://github.com/cypress-io/cypress/issues/30051

Examples caused by Renovate:

• https://github.com/cypress-io/cypress/pull/30008
• https://github.com/cypress-io/cypress/pull/29571

Manual error

Caused by manual change to a dependency in a package.json file without running yarn:

• https://github.com/cypress-io/cypress/pull/29781 but combined with an unclean PR https://github.com/cypress-io/cypress/pull/29770 from Renovate

[MikeMcC399]

GitHub Actions has a similar issue and https://github.com/cypress-io/github-action/blob/master/.github/workflows/check-dist.yml is used to check for unresolved changes.

That would be something like the following, added into the CI workflow at some point after yarn install has run:

if [ "$(git diff --ignore-space-at-eol | wc -l)" -gt "0" ]; then
    echo yarn.lock mismatch
    git diff
    exit 1
fi

[jennifer-shehane]

Yah, seems reasonable to have something in place since this keeps happening.

[MikeMcC399]

@jennifer-shehane

Yah, seems reasonable to have something in place since this keeps happening.

• Since the problem is mostly caused by Renovate, I suggest resolving https://github.com/cypress-io/cypress/issues/30051 first using the Renovate Yarn dedup option you pointed out. Edit: this PR has been merged. No new Renovate PRs have been generated since merger and there are still open Renovate PRs created before the change in Renovate parameters.

[MikeMcC399]

• PR https://github.com/cypress-io/cypress/pull/30060 has solved the regularly recurring issue for Renovate-generated PRs.
• This issue is nevertheless still relevant to catch manual mistakes even though they happen much less frequently than the Renovate issues were previously occurring.