Button: Keep deprecated props in type definitions

[mirka]

In preparation for #59733
Informed by feedback in #55401

What?

Tweaks how the deprecated props on Button are managed so that they are more permissive:

• Keep deprecated props in the TypeScript type definitions, so that they will be flagged as deprecated but not block TS compilation.
• Remove the hard deprecation version for the isDefault prop, since this is a very low maintenance back compat layer and we can pretty much keep it around indefinitely.

Why?

It's already been a while since these props have been deprecated, but I still think it's worthwhile to set some good patterns here before adding new deprecations like in #59734.

The main back compat considerations I think we should uphold are:

• Keep deprecated props in the type definitions so compilation does not fail, and to prevent future prop name collisions.
• Hard deprecations don't necessarily need to happen if the maintenance cost of the back compat layer is negligible.

Testing Instructions

• Type checks still pass
• Using one of the deprecated Button props should not throw a TS error
• The deprecated props should still be hidden from the Storybook props table (The JSDoc @ignore tag does this)

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Co-authored-by: mirka <0mirka00@git.wordpress.org>
Co-authored-by: tyxla <tyxla@git.wordpress.org>
Co-authored-by: andrewhayward <andrewhayward@git.wordpress.org>
Co-authored-by: t-hamano <wildworks@git.wordpress.org>

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[tyxla]

Looking good 👍

I wonder why we don't have deprecated() calls for the rest of these props though.

Could be a good idea for a follow-up.

[tyxla]

Any idea why we don't have deprecated() calls for the rest of the variant old props (like isSmall, isPrimary, etc.)?

[mirka]

I can't find an explicit reason being given, but it does look intentional.

[tyxla]

Looks like we just wanted to soft-deprecate first, and to hard-deprecate later: #31713 (comment)

It's been almost 3 years, so maybe it's about time for hard deprecation.

[tyxla]

Should we at least bump this so we still remove it in some future WP version?

[mirka]

It's the ambiguous back compat policy biting us again 😅

Up to this point the components package hasn't done many hard deprecations, mostly because a lot of these back compat layers are very low cost. Like virtually zero cost compared to the migration management cost we'd push to our third-party consumers who have to support multiple WP versions, and also the cost incurred on the end users who see incorrectly styled UI from all the consumers that never migrate.

And in that vein, I'm not particularly enthusiastic about logging deprecation warnings on "simple translation" API changes like this that really add no value to anyone. If we're not planning to hard deprecate, then there's no reason for consumers to migrate to the new API unless they want to for ergonomics or code quality reasons. I've been hearing that even managing these deprecation warnings while supporting multiple WP versions is cumbersome, so I don't consider them "free" even though they're dev-env only.

Happy to discuss and explicitly codify things a bit more, but I'm in no rush to hard deprecate things unless they have a tangible maintenance cost.

[andrewhayward]

Tweaks how the deprecated props on Button are managed so that they are more permissive:

• Keep deprecated props in the TypeScript type definitions, so that they will be flagged as deprecated but not block TS compilation.
• Remove the hard deprecation version for the isDefault prop, since this is a very low maintenance back compat layer and we can pretty much keep it around indefinitely.

This makes a lot of sense. I didn't realise we were removing deprecated props from the type definition, which is a bit weird if they're still technically supported 🚀

[t-hamano]

LGTM!

The code editor also appears to properly mark deprecated props.

The deprecation rule may need to be reaffirmed for the entire Gutenberg project, not just for components. The discussion in #46105, which attempted to remove deprecated APIs from component packages, might be helpful.