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Use output buffer and HTML tag processor to inject directives on BODY tag for full-page client-side navigation #61212

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merged 5 commits into from
May 27, 2024
Merged

Use output buffer and HTML tag processor to inject directives on BODY tag for full-page client-side navigation #61212

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bc71592
Inject client-side navigation directives via Tag Processor and output…
westonruter Apr 29, 2024
8bd0a3c
Fix typing for render_block phpdoc
westonruter Apr 29, 2024
29eeed4
Eliminate use of render_block filter
westonruter Apr 29, 2024
36fa0d2
Remove copy-pasta since tag
westonruter Apr 29, 2024
300d9e3
Ensure client-side directives are only added to HTML response bodies
westonruter Apr 29, 2024
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70 changes: 57 additions & 13 deletions lib/experimental/full-page-client-side-navigation.php
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Original file line number Diff line number Diff line change
Expand Up @@ -33,25 +33,69 @@ function _gutenberg_add_enhanced_pagination_to_query_block( $parsed_block ) {
add_filter( 'render_block_data', '_gutenberg_add_enhanced_pagination_to_query_block' );

/**
* Add directives to all links.
* Adds client-side navigation directives to BODY tag.
*
* Note: This should probably be done per site, not by default when this option is enabled.
*
* @param array $content The block content.
* @param string $response_body The response body.
*
* @return array The same block content with the directives needed.
* @return string The rendered template with modified BODY attributes.
*/
function _gutenberg_add_client_side_navigation_directives( $content ) {
$p = new WP_HTML_Tag_Processor( $content );
// Hack to add the necessary directives to the body tag.
// TODO: Find a proper way to add directives to the body tag.
static $body_interactive_added;
if ( ! $body_interactive_added ) {
$body_interactive_added = true;
return (string) $p . '<body data-wp-interactive="core/experimental" data-wp-context="{}">';
function _gutenberg_add_client_side_navigation_directives( $response_body ) {
$is_html_content_type = false;
foreach ( headers_list() as $header ) {
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In WordPress/performance#1189 I've improved on the testability of this by prepending 'Content-Type: ' . ini_get( 'default_mimetype' ) to this list.

$header_parts = preg_split( '/\s*[:;]\s*/', strtolower( $header ) );
if ( count( $header_parts ) >= 2 && 'content-type' === $header_parts[0] ) {
$is_html_content_type = in_array( $header_parts[1], array( 'text/html', 'application/xhtml+xml' ), true );
}
}
return (string) $p;
if ( ! $is_html_content_type ) {
return $response_body;
}

$p = new WP_HTML_Tag_Processor( $response_body );
if ( $p->next_tag( array( 'tag_name' => 'BODY' ) ) ) {
$p->set_attribute( 'data-wp-interactive', 'core/experimental' );
$p->set_attribute( 'data-wp-context', '{}' );
$response_body = $p->get_updated_html();
}
return $response_body;
}

// TODO: Explore moving this to the server directive processing.
add_filter( 'render_block', '_gutenberg_add_client_side_navigation_directives' );
add_filter( 'gutenberg_template_output_buffer', '_gutenberg_add_client_side_navigation_directives' );

/**
* Starts output buffering at the end of the 'template_include' filter.
*
* This is to implement #43258 in core.
*
* This is a hack which would eventually be replaced with something like this in wp-includes/template-loader.php:
*
* $template = apply_filters( 'template_include', $template );
* + ob_start( 'wp_template_output_buffer_callback' );
* if ( $template ) {
* include $template;
* } elseif ( current_user_can( 'switch_themes' ) ) {
*
* @link https://core.trac.wordpress.org/ticket/43258
*
* @param string $passthrough Value for the template_include filter which is passed through.
*
* @return string Unmodified value of $passthrough.
*/
function _gutenberg_buffer_template_output( string $passthrough ): string {
ob_start(
static function ( string $output ): string {
/**
* Filters the template output buffer prior to sending to the client.
*
* @param string $output Output buffer.
* @return string Filtered output buffer.
*/
return (string) apply_filters( 'gutenberg_template_output_buffer', $output );
}
);
Comment on lines +88 to +98
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Based on WordPress/performance#1317, I believe this should now rather be improved as follows:

Suggested change
ob_start(
static function ( string $output ): string {
/**
* Filters the template output buffer prior to sending to the client.
*
* @param string $output Output buffer.
* @return string Filtered output buffer.
*/
return (string) apply_filters( 'gutenberg_template_output_buffer', $output );
}
);
ob_start(
static function ( string $output ): string {
// When the output is being cleaned (e.g. pending template is replaced with error page), do not send it through the filter.
if ( ( $phase & PHP_OUTPUT_HANDLER_CLEAN ) !== 0 ) {
return $output;
}
/**
* Filters the template output buffer prior to sending to the client.
*
* @param string $output Output buffer.
* @return string Filtered output buffer.
*/
return (string) apply_filters( 'gutenberg_template_output_buffer', $output );
},
0,
PHP_OUTPUT_HANDLER_STDFLAGS ^ PHP_OUTPUT_HANDLER_FLUSHABLE
);

return $passthrough;
}
add_filter( 'template_include', '_gutenberg_buffer_template_output', PHP_INT_MAX );
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isn't an action just a filter whose return value is ignored? we could eliminate the $passthrough if we made this add_action() couldn't we?

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Unfortunately, add_action() defined as an alias:

function add_action( $hook_name, $callback, $priority = 10, $accepted_args = 1 ) {
	return add_filter( $hook_name, $callback, $priority, $accepted_args );
}

So if the callback doesn't return a value, then the filter is borked. I just tested:

diff --git a/lib/experimental/full-page-client-side-navigation.php b/lib/experimental/full-page-client-side-navigation.php
index 259517cfc84..452abee6c63 100644
--- a/lib/experimental/full-page-client-side-navigation.php
+++ b/lib/experimental/full-page-client-side-navigation.php
@@ -68,12 +68,8 @@ add_filter( 'gutenberg_template_output_buffer', '_gutenberg_add_client_side_navi
  *          } elseif ( current_user_can( 'switch_themes' ) ) {
  *
  * @link https://core.trac.wordpress.org/ticket/43258
- *
- * @param string $passthrough Value for the template_include filter which is passed through.
- *
- * @return string Unmodified value of $passthrough.
  */
-function _gutenberg_buffer_template_output( string $passthrough ): string {
+function _gutenberg_buffer_template_output() {
 	ob_start(
 		static function ( string $output ): string {
 			/**
@@ -85,6 +81,5 @@ function _gutenberg_buffer_template_output( string $passthrough ): string {
 			return (string) apply_filters( 'gutenberg_template_output_buffer', $output );
 		}
 	);
-	return $passthrough;
 }
-add_filter( 'template_include', '_gutenberg_buffer_template_output', PHP_INT_MAX );
+add_action( 'template_include', '_gutenberg_buffer_template_output', PHP_INT_MAX );

The result is an empty page because the if ( $template ) condition isn't entered here: https://github.com/WordPress/wordpress-develop/blob/204a1bbf4e5f22b07a93c1f4a0b12bdd65d6483f/src/wp-includes/template-loader.php#L105-L112

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darn. you've shattered my understanding of this. I guess do_action() simply ignores the return value, but apply_filter() doesn't care if something was added as a filter or an action.

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