Excerpts don't handle `innerBlocks` for groups and nested columns properly

[aristath]

See ​https://github.com/WordPress/gutenberg/issues/33154 for details.

When generating a post excerpt, we run the content through
excerpt_remove_blocks. That function doesn't currently handle innerBlocks for groups properly, as well as deeply-nested columns, resulting in empty excerpts.

[desrosj]

Added some feedback on the PR.

It would also be nice to get some unit tests added here.

[aristath]

Added some feedback on the PR.

Feedback addressed

It would also be nice to get some unit tests added here.

Tests added :)

[desrosj]

Thanks @aristath!

Just to pull in some context here, @aristath mentioned on the PR that it's desired to have this in 5.8.

Moving to 5.8 to consider.

[aristath]

Thank you @desrosj! 👍

[desrosj]

In 51348:

Posts: Prevent an empty excerpt when groups and nested column blocks are present.

This improves the logic within excerpt_remove_blocks() to better handle innerBlocks. This prevents an empty excerpt from being returned when core/columns, core/column, and core/group blocks are present.

This issue has been surfaced in the Query Loop block, where excerpts can be set to display.

Props aristath.
Fixes #53604.

[desrosj]

Reopening for backport consideration.

[jorbin]

@desrosj brought up in the code review including a filter and I feel like this is the right move. I don't think we should wait for 5.9 as it is going to make it more difficult for people that build custom blocks if we don't have it now.

[desrosj]

@aristath would you be able to create a follow up PR adding a filter? I'll wait to backport until after the filter is in.

Adds an excerpt_allowed_wrapper_blocks filter.

Trac ticket: https://core.trac.wordpress.org/ticket/53604

[aristath]

@aristath would you be able to create a follow up PR adding a filter? I'll wait to backport until after the filter is in.

Of course. Filter added in ​https://github.com/WordPress/wordpress-develop/pull/1479

[desrosj]

Never actually reopened this one. Reviewing the filter patch now.

[desrosj]

In 51375:

Posts: Allow the list of wrapper blocks to be filtered.

This introduces the excerpt_allowed_wrapper_blocks filter for controlling which blocks should be considered wrapper blocks.

Wrapper blocks and their nested contents are not stripped by excerpt_remove_blocks(), allowing their contents to appear in generated excerpts.

Follow up to [51348].

Props aristath, jorbin.
See #53604.

[desrosj]

@jorbin Can you review [51375] for backport when you have a chance?

Merged into Core in https://core.trac.wordpress.org/changeset/51375.

[SergeyBiryukov]

There's a "warppers" typo in the filter description, looks good to backport otherwise.

[jorbin]

Typo fixed, we should be good to backport all 3 together.

[jorbin]

[51378] didn't show up, but that is where the typo is fixed.

[jorbin]

In 51379:

Fix merge info.

[51378] contained merge info it shouldn't and accidentally a line of code from one of those commits that another one had changed.

See #53604.
Unprops jorbin.

[desrosj]

[51378] and [51379] look good to backport.

[jorbin]

In 51382:

Posts: Prevent an empty excerpt when groups and nested column blocks are present.

This improves the logic within excerpt_remove_blocks() to better handle innerBlocks. This prevents an empty excerpt from being returned when core/columns, core/column, and core/group blocks are present.

This issue has been surfaced in the Query Loop block, where excerpts can be set to display.

This introduces the excerpt_allowed_wrapper_blocks filter for controlling which blocks should be considered wrapper blocks.

Wrapper blocks and their nested contents are not stripped by excerpt_remove_blocks(), allowing their contents to appear in generated excerpts.

Backports [51348], [51375], [51378], and [51379] to the 5.8 branch.

Fixes #53604.
Props aristath, jorbin, SergeyBiryukov, desrosj.
Unprops jorbin.