Post Excerpt: Fix previews

[Mamaduka]

Description

Follow-up for #37622.

The preview filter applies content from autosave to the queries object (and global post). When we pass a post ID to the get_the_content, it uses an instance of the post where those changes aren't applied. Using null instead of $post_id in this scenario fixes the issue.

The same applies to the get_the_excerpt. PR removes the post ID argument to fix previews.

How has this been tested?

Using TT2 theme.

1. Update the "Single" template to use Post Excerpt.
2. Makes a change to a post without saving.
3. Click Preview -> Preview in new tab
4. Confirm that changes are reflected in the preview.

Types of changes

Bugfix

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[ntsekouras]

LGTM, thanks George!

I'm wondering though if this and the previous PR for post content/title, can create the impression to the user that the changes they see are saved, which they are not, and never push that Update button 😄

The difference between all the other previews is that they live in the editor and any pending unsaved changes are indicated by the status of the Update button.

In preview in new tab case could a notification that unsaved changes exist work better and not include these changes as before?
Or should we add such a complementary notification with the new functionality that states that the preview contains unsaved changes? 🤔

[Mamaduka]

Thanks for testing, Nik.

I'm wondering though if this and the previous PR for post content/title, can create the impression to the user that the changes they see are saved, which they are not, and never push that Update button 😄

It is hard to say without user testing, but I doubt it. The preview functionality is almost the same as in the classic editor.

Previewing posts will create an autosave so user can always restore their changes. Plus, they will be prompted with a confirmation modal when leaving the page.

Let's keep the fix simple for 5.9. We can always better highlight unsaved changes in previews in the future if needed.

Confirmation