Unintended coupling between WP Core version and Pantheon mu-plugin version

[schlessera]

This package currently ships the default Pantheon must-use plugin within its bundled wp-content folder, to ensure caching works as intended, etc...

However, there seems to be a package design flaw here which has created an unintended coupling between versions of WordPress Core and the Pantheon must-use plugin.

We had this issue with a large multisite we have migrated over to Pantheon. To ensure we didn't introduce any unintended changes during the migration, we opted for a Composer stack with fixed versions, and we pinned the WordPress Core version down to what the original site was using: WP Core 5.7.4.

However, this has led to a 2-year-old version of the Pantheon must-use plugin to be included instead, and this is the likely culprit of massive performance issues that we saw once the site went live.

I solved this by adding the https://github.com/pantheon-systems/pantheon-mu-plugin package to the Composer stack as well, and switching the old with the new versions during a Composer post-install script.

Ideally, this Composer setup would pull in the above package as a dependency that can be kept up-to-date on composer update, instead of bundling a fixed version of it.

[greg-1-anderson]

@schlessera You may pull in the pantheon-mu-plugin directly if you follow the example of the pantheon-systems/wordpress-composer-managed repository. This is in early access, but probably will work better for your needs than the bundled wordpress-composer project that you're currently using.

[jspellman814]

Tracking internally as BUGS-5622.

[jazzsequence]

It's worth noting that we are moving towards deprecating this repository in favor of WordPress (Composer Managed) which uses pantheon-systems/pantheon-mu-plugin by default.