Block API: Deprecate id prop in favor of clientId

[aduth]

Related: #6741 (comment)

This pull request seeks to propose deprecating the block id prop, which was never consistent, with a new standardization toward referencing a block's uid as its clientId. This is also intended as part of a capitalization normalization effort, where equivalent selectors and internal props are planned to be updated as well. The idea with the changes here are to deprecate early for the public-facing API, ahead of the upcoming 3.2 release.

Testing instructions:

Verify there are no regressions in the behavior of blocks.

To my knowledge, no core blocks use the id prop. You can add this to an existing block to test that the deprecated warning is shown, but the behavior of id is otherwise unaffected.

Related: Confirmation that destructuring of objects triggers getters (and therein the deprecated), thus not requiring a warning to be shown except in the case of blocks making use of this prop:

https://codepen.io/aduth/pen/VdRmav?editors=1111

[jorgefilipecosta]

thus not requiring a warning to be shown except in the case of blocks making use of this prop

Hi @aduth, the changes look good, but In my tests, If I create a new post and I press the "Write your story" placeholder I see the warning right away even though we are not using the id attribute. May some debugging tool is causing the message to appear.
I used this test block https://gist.github.com/jorgefilipecosta/aa2cc6c59e6e53279e5b04607510dc58 that uses id and things worked as expected.

[aduth]

Hmm, good catch @jorgefilipecosta . I'm not sure why I wasn't seeing or didn't notice that previously. I suppose it could make sense if React is iterating over the props that the getter is inevitably going to be called. To move forward, I'm wondering:

• Do we just make the breaking change now, notably because this prop has never been documented.
• Do we warn for all developers about the deprecation, maybe once at page load?

[aduth]

Rebased to resolve conflicts. I decided to just add a global warning to edit-post/index.js, which we can remove with the prop passing in 3.4. What do you think, @jorgefilipecosta ?

[jorgefilipecosta]

Looks good to be 👍 A global deprecation message seems to be the best option in this case.
I did some grepping and I did not find any usages of id in core-blocks.