Query block duplicate "read more" link

[draganescu]

Description

When using a classic theme (e.g. Twenty Fifteen) and using a posts list block in a post (for example to create an index to related content in a category), one can end up with duplicated read more links:

Step-by-step reproduction instructions

1. Have WordPress 5.9
2. Go to Appearance > Themes
3. Activate Twenty Fifteen
4. Make a post with an excerpt and content, set it to a category
5. Make a post without an excerpt but with content, set it to the category at 4
6. In a new post insert a Posts List block
7. Setup the block to show the category you used at 4 and 5
8. Check that order by is Newest to oldest
9. Notice bug: the post without excerpt will show "continue reading". If one adds a read more link text in the Post List block, the posts with no excerpt will get a duplicated link.

Screenshots, screen recording, code snippet

Environment info

WordPress 5.9
Gutenberg trunk

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[carolinan]

I believe this has been brought up before, but it is difficult to search the GitHub repo, so I don't have the link ready right now.

Twenty Fifteen adds the following code:

			the_content(
				sprintf(
					/* translators: %s: Post title. */
					__( 'Continue reading %s', 'twentyfifteen' ),
					the_title( '<span class="screen-reader-text">', '</span>', false )
				)
			);

I don't know how the block could be made aware of that 🤔.

[draganescu]

I did search as well but could not find something as well.

[ntsekouras]

I think this would be very hard to detect as is the case for similar php filters and the consistency between editor and front end. A similar case for Post Excerpt was this one: #33366.

[draganescu]

Random idea to check if the excerpt ends in an anchor. :)

[draganescu]

This is likely to never get a fix (see #38748) as the solutions would be very fragile and the situation is very exotic.

[ntsekouras]

I have a POC from a while ago with another approach. It could use some feedback/thoughts 😄

[draganescu]

@ntsekouras is #38662 more likely to solve #22269 ?