REST API: Expose permalink_template in the Posts controller

[danielbachhuber]

In ​WordPress/gutenberg#5756, editable permalink previews landed in Gutenberg.

We need to take this same information and expose it on the Posts controller:

function gutenberg_add_permalink_template_to_posts( $response, $post, $request ) {
	if ( 'edit' !== $request['context'] ) {
		return $response;
	}

	if ( ! function_exists( 'get_sample_permalink' ) ) {
		require_once ABSPATH . '/wp-admin/includes/post.php';
	}

	$sample_permalink = get_sample_permalink( $post->ID, $post->post_title, '' );

	$response->data['permalink_template'] = $sample_permalink[0];
	$response->data['generated_slug']     = $sample_permalink[1];

	return $response;
}

This data should reflect the assumptions already established in edit-form-advanced.php (e.g. post type must be viewable and public).

Related #41014

[sanchothefat]

Question: shouldn't this information be part of the Post Types controller responses if not just exposed via wp_localize_script() or similar?

[danielbachhuber]

Replying to sanchothefat:

Question: shouldn't this information be part of the Post Types controller responses if not just exposed via wp_localize_script() or similar?

The Posts controller seems to make most sense at this point. The value of both permalink_template and generated_slug are dependent on the computed value of $post->ID and $post->post_title, and could vary from post to post (e.g. through filters).

Also, we want to expose this information through the REST API so that other clients (e.g. mobile apps) have access to it. wp_localize_script() doesn't provide this for us.

[sanchothefat]

Replying to danielbachhuber:

Replying to sanchothefat:

Question: shouldn't this information be part of the Post Types controller responses if not just exposed via wp_localize_script() or similar?

The Posts controller seems to make most sense at this point. The value of both permalink_template and generated_slug are dependent on the computed value of $post->ID and $post->post_title, and could vary from post to post (e.g. through filters).

Also, we want to expose this information through the REST API so that other clients (e.g. mobile apps) have access to it. wp_localize_script() doesn't provide this for us.

Thanks, I thought the permalink_template was the generic value set when registering a post type or via the permalinks settings page.

[rahulsprajapati]

Expose permalink_template and generated_slug from title in the Posts controller with phpunit test.

[danielbachhuber]

Thanks @rahulsprajapati

A couple points of feedback on the patch:

1. The permalink_template and generated_slug attributes both need to be defined on the object's schema, but only when the post type is public and viewable. See:
   • https://core.trac.wordpress.org/browser/tags/4.9.8/src/wp-admin/edit-form-advanced.php#L101
   • https://core.trac.wordpress.org/browser/tags/4.9.8/src/wp-admin/edit-form-advanced.php#L600
2. The permalink_template and generated_slug attributes should always be added to the response, as they're dynamically removed by the call to $this->filter_response_by_context().

[rahulsprajapati]

Resolved feedback from comment #5.

[danielbachhuber]

@rahulsprajapati Looking pretty good!

One last suggestion: it'd be great to have a test that registered a non-public custom post type and asserted neither permalink_template nor generated_slug were on the schema and in the Post response.

My hunch is that, with 45017.2.diff, permalink_template and generated_slug will be included on the Post response accidentally because they aren't defined in the schema. We'll need to apply the if ( is_post_type_viewable( $post_type_obj ) && $post_type_obj->public ) { conditional in prepare_item_for_response() too.

[rahulsprajapati]

Replying to danielbachhuber:

@rahulsprajapati Looking pretty good!

One last suggestion: it'd be great to have a test that registered a non-public custom post type and asserted neither permalink_template nor generated_slug were on the schema and in the Post response.

My hunch is that, with 45017.2.diff, permalink_template and generated_slug will be included on the Post response accidentally because they aren't defined in the schema. We'll need to apply the if ( is_post_type_viewable( $post_type_obj ) && $post_type_obj->public ) { conditional in prepare_item_for_response() too.

Yeah, that is possible - will update this changes soon.

[rahulsprajapati]

Resolved feedback from comment:6

[danielbachhuber]

45017.3.diff looks great to me. Before we land this, we'll want to:

1. Apply the patch to core.
2. Comment out the corresponding code in Gutenberg.
3. Verify Gutenberg works as expected using this patch.

[danielbachhuber]

In 45017.4.diff, I've:

1. Cleaned up the tests to be a bit more literal and understandable.
2. Fixed the response data inclusion to respect any ?_fields= defined for the request.
3. Updated more tests accordingly so the entire suite passes.
4. Disabled the assertion with filter_rest_url_for_leading_slash when we have pretty permalinks. The origin was ​WP-API/WP-API#2428 which wasn't designed for tests with pretty permalinks.

I've also verified Gutenberg continues to work as expected with this patch.

[danielbachhuber]

In 43720:

REST API: Include permalink_template/generated_slug for Posts

In order for clients to present permalink previews, the REST API must share the computed results of get_sample_permalink(). These two values are now exposed as permalink_template and generated_slug for public, viewable post types, but only for context=edit.

Props danielbachhuber, rahulsprajapati.
Fixes #45017.

[danielbachhuber]

Reopening for merging to trunk.

[danielbachhuber]

In 43766:

REST API: Ensure rest_url() consistently has leading slash.

rest_url() inconsistent addes slashes to the passed path depending on whether the site has pretty permalinks enabled. Apart from being inconsistent, this also caused the unit tests to fail when pretty permalinks are enabled.

Props frank-klein.
Merges [42250] to the 5.0 branch.
Partially reverts [43720].
Fixes #42452. See #41451, #45017.

[ocean90]

#45364 was marked as a duplicate.

[jeremyfelt]

In 43980:

REST API: Include permalink_template/generated_slug for Posts

In order for clients to present permalink previews, the REST API must share the computed results of get_sample_permalink(). These two values are now exposed as permalink_template and generated_slug for public, viewable post types, but only for context=edit.

Merges [43720] to trunk.

Props danielbachhuber, rahulsprajapati.
Fixes #45017.