fix #22550 and allow enter to insert line breaks even if template is locked

[oxyc]

Description

See #22550. I have no idea what I'm doing, I'm just opening up this PR for discussion and the off chance that this is actually okay. Ping @ellatrix or someone who actually knows what's happening in this flow should have a look.

Note that this is how it used to work at least some versions back.

How has this been tested?

1. Added a template to the post post type.

add_action('init', function () {
    $post_type_object = get_post_type_object('post');
    $post_type_object->template = [
      [ 'core/paragraph', [
        'placeholder' => 'test'
      ] ],
      [ 'core/list', [
        'placeholder' => 'test'
      ] ],
    ];
    $post_type_object->template_lock = 'all';
});

2. Pressed enter and shift-enter to check that both add a soft line break.
3. Press backspace and ensure the block is not removed.

Screenshots

Types of changes

Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• 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.

[ellatrix]

Ideally would be best to not have content from the previous test. Not a blocker though. :)

[ocean90]

I don't think that this should work for Enter too. Only Shift+Enter is kind of known for inserting a soft line break.

[oxyc]

I'd disagree lots of my clients are not aware of that and silently treating Enter as a soft line break is a much nicer UX if you have an entire post type locked. This is also how it used to work before the regression.

[smerriman]

Not sure if this is the right place to post, but I would like to agree with @ocean90 and have this reverted to only apply to Shift+Enter. I'm not sure what pressing Enter did in the past, but what it should do is exit the block, like it does when pushing Enter after any other paragraph block.

[smerriman]

Just as a use case, I'm setting up a simple block which allows someone to enter one paragraph, and display an icon beside it (using the ACF plugin with InnerBlocks locked to one paragraph, and an image field).

This works fine, but I keep hitting enter after that paragraph so that I can type a normal paragraph, and instead end up with a line break inside the original block.