Framework: Bootstrap Block Templates

[youknowriad]

This PR is the first one introducing the Block Templates. (details on those here #3588 )
This first iteration allows:

• Defining a template for a CPT
• Initialize the editor with a predefined list of blocks if a template is found.

A template object looks like this:

const template = [
  [ 'block/name', {} ], // [ blockName, attributes ]
];

Testing instructions

• Add A CPT like this:

function register_book_type() {
	$args = array(
		'public' => true,
		'label'  => 'Books',
		'show_in_rest' => true,
		'template' => array(
			array( 'core/image' ),
			array( 'core/paragraph', array(
				'placeholder' => 'Add a book description',
			) ),
			array( 'core/quote' ),
		),
	);
	register_post_type( 'book', $args );
}
add_action( 'init', 'register_book_type' );

• Create a new post with the registered CPT
• The editor should initialize with the predefined list of blocks defined in this template.

Notes

• Block Attributes need to be initialized properly server-side, we should move away from our Editable Value as React Elements to be able to do so for these attributes (related Editable: state as a cleaned up tree #3048)

[codecov]

Codecov Report

Merging #3668 into master will decrease coverage by 0.01%.
The diff coverage is 20%.

@@            Coverage Diff            @@
##           master   #3668      +/-   ##
=========================================
- Coverage   37.32%   37.3%   -0.02%     
=========================================
  Files         277     277              
  Lines        6685    6690       +5     
  Branches     1213    1214       +1     
=========================================
+ Hits         2495    2496       +1     
- Misses       3532    3536       +4     
  Partials      658     658

Impacted Files	Coverage Δ
editor/actions.js	47.16% <ø> (ø)	⬆️
editor/components/provider/index.js	13.33% <0%> (+0.83%)	⬆️
editor/effects.js	58.06% <28.57%> (-2.11%)	⬇️

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[mtias]

Are we sure we are going to want additional properties on the template object instead of making template = template.blocks?

[youknowriad]

I don't know honestly. Server-side I think so, because templates could have a name/description but client-side I don't really know. I thought we should do this to avoid future breaking changes.

[mtias]

Yes, just thinking out-loud. There are things like "locking" which might be interesting there. Not sure about naming templates, but maybe an id / slug if they are stored somewhere?

[mtias]

Thinking further, I can't see why we would pair defining blocks and naming in the CPT. If anything, the "template" would be defined outside the CPT and referenced here by slug.

Also, things like locking could be defined as another attribute of the CPT registration, which seems more in line with how we generally structure options:

'template' => array(
	array( 'core/image' ),
	array( 'core/paragraph', array(
		'placeholder' => 'Add a book description',
	) ),
	array( 'core/quote' ),
),
'template_lock' => true,

Finally, what do you think of simplifying the syntax to not require name => 'core/heading'? I think we can rely on the definition of a block to be array( blockName, attributes ... ).

[youknowriad]

Sure, I was not sure about the extra keys anyway.

[mtias]

I love that this fairly low profile implementation wise.

[mtias]

This is looking good to me. We probably want to add a test and some documentation. I think we might need a new "Templates" document. (Doesn't have to block this.)

[youknowriad]

Merged, let's add the docs and tests separately.

[aduth]

Notice: Undefined property: WP_Post_Type::$template in /srv/www/editor/htdocs/wp-content/plugins/gutenberg/lib/client-assets.php on line 786

I suggest running with high error reporting:

error_reporting( E_ALL );

(Add near top of site root index.php)

[aduth]

You want empty here:

if ( ! empty( $post_type_object->template ) ) {

[baerkins]

I'm not sure if this is intended, but omitting 'show_in_rest' => true, or setting it to false results in the default editor appearing.

[youknowriad]

@iamhexcoder Yes, this is expected. Gutenberg uses the REST API and if the show_in_rest is false, Gutenberg is not able to fetch an save the CPT. This is a current limitation of the REST API.

We'll figure out a way to solve this. Tracked in #3066