Plans Next: Remove all of Redux plans state and manage it through the Plans data-store (main thread)

[chriskmnds]

What

Migrate/replace the Redux plans state (selectors and query components) to happen through the plans data store under /packages/data-stores/plans.

Why

Since https://github.com/Automattic/wp-calypso/pull/86349 we have effectively turned the existing plans' state redundant (which is primarily used for pricing). We are now maintaining two completely separated forms of state handling, one through the monolithic Redux state and another through the data-stores package. This needs some ownership to clean up the trace for the greater well-being of the codebase.

How

The following can be done through individual PRs:

• start from getPlanPrices selector (it should be straight-up replaceable by Plans.usePricingMetaForGridPlans)
• continue with all the calls to the various selectors from /client/state/plans and /client/state/sites/plans - these are replaceable with respective calls to either Plans.usePricingMetaForGridPlans or Plans.usePlans and Plans.useSitePlans (both delivering the respective pricing state)
• continue with removing query components under /client/data
• continue with removing relevant reducers
• update the types in /packages/data-store/plans to reflect only the remaining (used) properties needed in the new selectors (and/or add whatever new properties are needed)
• align the actual endpoint code (backend) with what's needed on the frontend e.g. to stop sending redundant properties through (like orig_cost or raw_price that are no longer needed)

[chriskmnds]

Update 12/07/2024

Just a quick update on progress:

• We shipped several PRs referenced above, with https://github.com/Automattic/wp-calypso/pull/92589 effectively handling removal of the logged-out plans state. This is the first piece in the puzzle taken care of.

Also noting a point of exploration (that may lead to a detour before proceeding with site-plans):

• Apparently, currency-code is partially dependent on plans and products being populated in the state tree. Our intention is to migrate both plans and products to data-stores, as we have complete state coverage there. So at any point we will need to strip off currency-code and have it handled via some data-store hook.
• It looks hefty with 25+ references of getCurrentUserCurrencyCode in the code, with several in Class components that require additional wrapping/refactoring to utilize hooks.