Misleading More text after saving an empty text

[ntsekouras]

Describe the bug
With the current behaviour of More block, if we change the text to an empty string and update, we will save an undefined value. This leads into taking the default value of More block that is Continue Reading.

So if we refresh the page later will show the JS default value: Read more but actually doesn't have a value.

To reproduce
Steps to reproduce the behavior:

1. Go to a post and add a More block
2. Empty the More text and update
3. Refresh the page and watch that Read more is shown
4. View the post's category page in front end and watch that Continue Reading is shown

Expected behavior
A user shouldn't be able to save an empty text for More block. On focusing out the input, it should change to the default JS value Read more.

Screenshots

When we save.

After reloading the post

What is shown in front-end

[mcsf]

Steps to reproduce the behavior:

1. Go to a post and add a More block
2. Empty the More text and update
3. Refresh the page and watch that Read more is shown
4. View the post's category page in front end and watch that Continue Reading is shown

As a user, what did you expect to happen in the editor once you emptied the text input? And in the front end?

[mcsf]

The More block was added fairly early on in the development of Gutenberg and it sought to mimic the functionality provided with TinyMCE. This explains why it's such a simple block and why its editor view is so detached from the front-end result.

It's also a block that doesn't tend to receive a lot of attention, and so it has remained like this for a long time.

More importantly, until Phase 2, Gutenberg has only concerned itself with the post_content. Thus, it made sense to render More as a very discreet line, because the rendered post will have no visual cue at all.

However, as we move into full-site editing (FSE) territory, it will probably be good to revisit More in such a way that it can behave differently depending on the editing content:

• When editing a single post (like today), More should merely appear as a dashed line (like today).
• In FSE, when editing a page that has a list of posts (e.g. an archive view), the More blocks corresponding to each post should be rendered faithfully (i.e. an actual button matching the theme).
• The same situation applies when using the Query block : it should be possible to render faithful More blocks among the blocks nested in Query.

Ideally, the FSE work with More in mind would make it easier to determine what the server-side $more_link_text will be in the case of an absent customText value for the More block. And then we won't have to hack the value of customText as initially attempted in #23758. :)

[ntsekouras]

As a user, what did you expect to happen in the editor once you emptied the text input? And in the front end?

Probably be empty both at admin and front-end.

[ntsekouras]

I'm closing this issue as it seems FSE development/evolution is a better place to revisit, maybe reinvent, as described by @mcsf above.