What?

Follow up of: #76441

PostTemplatePanel has complex logic that has been iterated over the years to handle differently different combinations of block, classic and hybrid themes that have custom templates or not, permissions etc..

In the linked PR I update the template field to match the template panel controls but there are a few more nuances.

I observed two cases that didn't match, that needed to be handled in DataFormPostSummary component.

1. A classic theme with no templates (2015) in the post summary doesn't render the panel at all. This PR excludes the field from the form in that case
2. A classic theme with no templates (2015) but with added template support through code, in the post summary renders a default template. With the experiment this translates to making the field readonly.

Snippet to add template support

add_action( 'after_setup_theme', 'mytheme_setup' );
function mytheme_setup() {
    add_theme_support( 'block-templates' );
    add_theme_support( 'block-template-parts' );
}

Testing Instructions

1. What I did was testing various type of themes, with and without template support, with and without existing templates (in case of classic themes). I'm sharing a lot of screenshots below that are examples of the different scenarios.
2. The above also need to happen by enabling/disabling the Editor Inspector: Use DataForm experiment for each case to validate matching behaviors.
3. The results should match.
4. Ensure that without the experiment there is no regression by extracting the logic in the reusable hook.

Notes

While testing I observed a bug in the existing code for classic themes that had previously template support and created templates. The control shows the created templates, but this doesn't work if the template support is not enabled and errors. I have screenshot below.

Block theme 2025

It's expected that the template panel has actions and not the DataForm field. Actions are moved here.

Experiment disabled	Enabled

2015 classic theme - It has no available templates

The template panel or field are not rendered

Experiment disabled	Enabled

2015 classic theme - It has no available templates - but with added template support

Experiment disabled	Enabled

2014 classic theme - It has available templates

In the disabled screenshot you can see the bug I mention above with previously created templates even if now it didn't have template support.

Experiment disabled	Enabled

2014 classic theme - It has available templates - but with added template support

Experiment disabled	Enabled