Gutenberg: Fix nested template files in WP

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Summary

• The current template synchronization is not working well with template files in nested folder

• Propose solution to create a post meta for storing the path of the template files as post meta

  • On saving the modified template, add new post meta on creating record: API endpoint, File? . This still replace hyphen to post name
  • Template actions - Edit-site store removeTemplate - Pattern grid duplication
  • On block template retrieval get_items, use post meta instead of post name in synchronisation process. Which function? Which API endpoint?

• Code navigation

  • _get_block_templates_files
  • _sanitize_template_id: double slash mechanism
  • WP_REST_Templates_Controller: wp_template_part custom post type and rest handler
  • Template rest get_items

• According to this, we can modify the Wordpress code directly in Gutenberg repo? gutenberg/lib/compat/wordpress-5.9

  • Try to override the default WP files in wp_includes: copy the file from wp_includes to lib/compact/{wordpress_version}
  • Update the include in lib/load.php

• Look at the 2 method in core and Gutenberg

  • Core: get_default_block_template_types - Gutenberg: gutenberg_get_default_block_template_types
  • Core: return apply_filters( 'default_template_types', $default_template_types );
  • Gutenberg: add_filter( 'default_template_types', 'gutenberg_get_default_block_template_types', 10 );

  • Here's a simplified version of what happens:

    1. get_default_block_template_types() is called.
    2. This function generates an array of default block template types.
    3. The default_template_types filter is applied to this array.
    4. Because gutenberg_get_default_block_template_types is hooked to this filter, it is called with the array as its argument.
    5. gutenberg_get_default_block_template_types modifies the array and returns it.
    6. The modified array is returned by get_default_block_template_types().

This allows the Gutenberg plugin to modify the default block template types provided by WordPress.

Reference

• Issue#54279
• PR#54889
• Template synchronization process notes
• Potential related issue An incorrect template part slugs when the theme folder name ends with parts
• https://wisdmlabs.com/blog/guide-to-finding-appropriate-hooks-in-a-wordpress-theme-or-plugin/

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Override template utils

Filter pre_get_block_templates

• The function will expect 3 params, if missing the first null variable at start, it will fail

  
  function gutenberg_get_block_templates( $query_result = null, $query = array(), $template_type = 'wp_template' ) {}

add_filter( 'pre_get_block_templates', 'gutenberg_get_block_templates', 10, 2 );

- Current `$template_type` is always bound to the initial value as wp_template or wp_template_part...

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Override Rest Class

• Gutenberg_REST_Blocks_Controller inherit WP_REST_Blocks_Controller
• Again Gutenberg_REST_Block_Patterns_Controller_6_3 inherits Gutenberg_REST_Blocks_Controller
• Those classes are defined in 6.3 compact and is inherited Gutenberg_REST_Block_Patterns_Controller
• Again this class is registered in rest to override default WP Rest class

For Rest Template Controller

• WP_REST_Templates_Controller instance on Wordpress
• Create new class Gutenberg_REST_Templates_Controller to inherit current WP_REST_Templates_Controller
• Override rest_controller_class props for wp_template and wp_template_part
• Similar to wp_block rest_controller_class overriding using filter register_post_type_args, we can mimic the changes for template posts

More findings

• Actually Gutenberg_REST_Template_Revision_Count has been introduced to override Template REST on 6.3 already, we can take advantage of this instead
• Add more meta to post type, custom-fields should be supported, similar to gutenberg_add_custom_fields_to_wp_block
• Example of adding new post meta wp_pattern_sync_status

Saving template content to database

• meta_input set to origin, does it mean origin is a post meta for the templates?
  • What is "meta_input" parameter in wp_insert_post() used for?

Template files retrival

• Inside get_block_template WP will scan all the file templates in the theme folder, we can take advantage of this to insert the file path data to Template object
• get_block_theme_folders, default folders are templates and parts
• _get_block_template_file where the $new_template_item is created

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How template path retrieve

• Block Templates is queried from database + theme folder with _get_block_templates_files

• Absolute paths is retrieved in _get_block_templates_paths

• path prop is assigned in returned template file

• title is provided in _add_block_template_info

• Note that _get_block_template_file is different from _get_block_templates_files, one for single and one for multi files

• But both methods call the _add_block_template_info (wp_template) and _add_block_template_part_area_info (wp_template_part) to insert missing meta data for the object

• Template file template_slug is the one extracted directly from file path (it will store correct file paths with folder), stripped .html, we can restore it as meta path

• nit: if the templates are modified and saved in database, their slugs will be extracted and skipped query from files $query['slug__not_in'] = wp_list_pluck( $query_result, 'slug' );

• We may need to intercept this behavior by check it against the real path not the slug

• Rough steps

  1. On post creation in Rest template, save the template slug (slug is correctly parse from template file at this phase) to a post meta
  2. On template retrieval, update slug__not_in with the path meta, not the slug