<?php
/**
* Speculative loading functions.
*
* @package WordPress
* @subpackage Speculative Loading
* @since 6.8.0
*/
/**
* Returns the speculation rules configuration.
*
* @since 6.8.0
* @since 7.1.0 The `WP_SPECULATIVE_LOADING_DEFAULT_MODE` and `WP_SPECULATIVE_LOADING_DEFAULT_EAGERNESS` constants and
* environment variables can now specify the default mode and eagerness, respectively.
*
* @see wp_get_speculation_rules_default_configuration()
*
* @return array<string, string>|null Associative array with 'mode' and 'eagerness' keys, or null if speculative
* loading is disabled.
* @phpstan-return array{
* mode: 'prefetch'|'prerender',
* eagerness: 'conservative'|'moderate'|'eager',
* }|null
*/
function wp_get_speculation_rules_configuration(): ?array {
// By default, speculative loading is only enabled for sites with pretty permalinks when no user is logged in.
if ( ! is_user_logged_in() && get_option( 'permalink_structure' ) ) {
$config = array(
'mode' => 'auto',
'eagerness' => 'auto',
);
} else {
$config = null;
}
/**
* Filters the way that speculation rules are configured.
*
* The Speculation Rules API is a web API that allows to automatically prefetch or prerender certain URLs on the
* page, which can lead to near-instant page load times. This is also referred to as speculative loading.
*
* There are two aspects to the configuration:
* * The "mode" (whether to "prefetch" or "prerender" URLs).
* * The "eagerness" (whether to speculatively load URLs in an "eager", "moderate", or "conservative" way).
*
* By default, the speculation rules configuration is decided by WordPress Core ("auto"). This filter can be used
* to force a certain configuration, which could for instance load URLs more or less eagerly.
*
* For logged-in users or for sites that are not configured to use pretty permalinks, the default value is `null`,
* indicating that speculative loading is entirely disabled.
*
* @since 6.8.0
* @see https://developer.chrome.com/docs/web-platform/prerender-pages
*
* @param array<string, string>|null $config Associative array with 'mode' and 'eagerness' keys, or `null`. The
* default value for both of the keys is 'auto'. Other possible values
* for 'mode' are 'prefetch' and 'prerender'. Other possible values for
* 'eagerness' are 'eager', 'moderate', and 'conservative'. The value
* `null` is used to disable speculative loading entirely.
*/
$config = apply_filters( 'wp_speculation_rules_configuration', $config );
// Allow the value `null` to indicate that speculative loading is disabled.
if ( null === $config ) {
return null;
}
// Sanitize the configuration and replace 'auto' with current defaults.
$defaults = wp_get_speculation_rules_default_configuration();
$default_mode = $defaults['mode'];
$default_eagerness = $defaults['eagerness'];
if ( ! is_array( $config ) ) {
return array(
'mode' => $default_mode,
'eagerness' => $default_eagerness,
);
}
if (
! isset( $config['mode'] ) ||
'auto' === $config['mode'] ||
! WP_Speculation_Rules::is_valid_mode( $config['mode'] )
) {
$config['mode'] = $default_mode;
}
if (
! isset( $config['eagerness'] ) ||
'auto' === $config['eagerness'] ||
! WP_Speculation_Rules::is_valid_eagerness( $config['eagerness'] ) ||
// 'immediate' is a valid eagerness, but for safety WordPress does not allow it for document-level rules.
'immediate' === $config['eagerness']
) {
$config['eagerness'] = $default_eagerness;
}
return array(
'mode' => $config['mode'],
'eagerness' => $config['eagerness'],
);
}
/**
* Returns the default speculation rules configuration that the value 'auto' resolves to.
*
* WordPress Core defaults to a mode of 'prefetch' and an eagerness of 'conservative'. Hosting providers can override
* either default by way of the `WP_SPECULATIVE_LOADING_DEFAULT_MODE` and `WP_SPECULATIVE_LOADING_DEFAULT_EAGERNESS`
* constants or environment variables. This only changes what the 'auto' value resolves to, so a plugin which supplies
* an explicit mode or eagerness via the {@see 'wp_speculation_rules_configuration'} filter continues to take
* precedence.
*
* Note that an eagerness of 'immediate' is not permitted as a default, since WordPress does not allow it for the
* document-level rules that it generates.
*
* @since 7.1.0
* @access private
*
* @return array<string, string> Associative array with 'mode' and 'eagerness' keys.
* @phpstan-return array{
* mode: 'prefetch'|'prerender',
* eagerness: 'conservative'|'moderate'|'eager',
* }
*/
function wp_get_speculation_rules_default_configuration(): array {
$default_mode = 'prefetch';
$mode = wp_get_speculative_loading_override( 'WP_SPECULATIVE_LOADING_DEFAULT_MODE' );
if ( WP_Speculation_Rules::is_valid_mode( $mode ) ) {
$default_mode = $mode;
}
$default_eagerness = 'conservative';
$eagerness = wp_get_speculative_loading_override( 'WP_SPECULATIVE_LOADING_DEFAULT_EAGERNESS' );
if (
WP_Speculation_Rules::is_valid_eagerness( $eagerness ) &&
// 'immediate' is a valid eagerness, but for safety WordPress does not allow it for document-level rules.
'immediate' !== $eagerness
) {
$default_eagerness = $eagerness;
}
return array(
'mode' => $default_mode,
'eagerness' => $default_eagerness,
);
}
/**
* Returns the value of a speculative loading override, as supplied by a constant or an environment variable.
*
* The constant takes precedence over the environment variable, consistent with {@see wp_get_environment_type()}.
*
* @since 7.1.0
* @access private
*
* @param string $name Name of the constant and environment variable to look up.
* @return string|null The override value, or null if neither is set.
*/
function wp_get_speculative_loading_override( string $name ): ?string {
$value = null;
// Check if the environment variable has been set, if `getenv` is available on the system.
if ( function_exists( 'getenv' ) ) {
$has_env = getenv( $name );
if ( false !== $has_env ) {
$value = $has_env;
}
}
// Fetch the value from a constant, which overrides the environment variable.
if ( defined( $name ) ) {
$has_constant = constant( $name );
if ( is_string( $has_constant ) ) {
$value = $has_constant;
}
}
return $value;
}
/**
* Returns the full speculation rules data based on the configuration.
*
* Plugins with features that rely on frontend URLs to exclude from prefetching or prerendering should use the
* {@see 'wp_speculation_rules_href_exclude_paths'} filter to ensure those URL patterns are excluded.
*
* Additional speculation rules other than the default rule from WordPress Core can be provided by using the
* {@see 'wp_load_speculation_rules'} action and amending the passed WP_Speculation_Rules object.
*
* @since 6.8.0
* @access private
*
* @return WP_Speculation_Rules|null Object representing the speculation rules to use, or null if speculative loading
* is disabled in the current context.
*/
function wp_get_speculation_rules(): ?WP_Speculation_Rules {
$configuration = wp_get_speculation_rules_configuration();
if ( null === $configuration ) {
return null;
}
$mode = $configuration['mode'];
$eagerness = $configuration['eagerness'];
$prefixer = new WP_URL_Pattern_Prefixer();
$base_href_exclude_paths = array(
$prefixer->prefix_path_pattern( '/wp-*.php', 'site' ),
$prefixer->prefix_path_pattern( '/wp-admin/*', 'site' ),
$prefixer->prefix_path_pattern( '/*', 'uploads' ),
$prefixer->prefix_path_pattern( '/*', 'content' ),
$prefixer->prefix_path_pattern( '/*', 'plugins' ),
$prefixer->prefix_path_pattern( '/*', 'template' ),
$prefixer->prefix_path_pattern( '/*', 'stylesheet' ),
);
/*
* If pretty permalinks are enabled, exclude any URLs with query parameters.
* Otherwise, exclude specifically the URLs with a `_wpnonce` query parameter or any other query parameter
* containing the word `nonce`.
*/
if ( get_option( 'permalink_structure' ) ) {
$base_href_exclude_paths[] = $prefixer->prefix_path_pattern( '/*\\?(.+)', 'home' );
} else {
$base_href_exclude_paths[] = $prefixer->prefix_path_pattern( '/*\\?*(^|&)*nonce*=*', 'home' );
}
/**
* Filters the paths for which speculative loading should be disabled.
*
* All paths should start in a forward slash, relative to the root document. The `*` can be used as a wildcard.
* If the WordPress site is in a subdirectory, the exclude paths will automatically be prefixed as necessary.
*
* Note that WordPress always excludes certain path patterns such as `/wp-login.php` and `/wp-admin/*`, and those
* cannot be modified using the filter.
*
* @since 6.8.0
*
* @param string[] $href_exclude_paths Additional path patterns to disable speculative loading for.
* @param string $mode Mode used to apply speculative loading. Either 'prefetch' or 'prerender'.
*/
$href_exclude_paths = (array) apply_filters( 'wp_speculation_rules_href_exclude_paths', array(), $mode );
$href_exclude_paths = array_filter( $href_exclude_paths, 'is_string' );
// Ensure that:
// 1. There are no duplicates.
// 2. The base paths cannot be removed.
// 3. The array has sequential keys (i.e. array_is_list()).
$href_exclude_paths = array_values(
array_unique(
array_merge(
$base_href_exclude_paths,
array_map(
static function ( string $href_exclude_path ) use ( $prefixer ): string {
return $prefixer->prefix_path_pattern( $href_exclude_path );
},
$href_exclude_paths
)
)
)
);
$speculation_rules = new WP_Speculation_Rules();
$main_rule_conditions = array(
// Include any URLs within the same site.
array(
'href_matches' => $prefixer->prefix_path_pattern( '/*' ),
),
// Except for excluded paths.
array(
'not' => array(
'href_matches' => $href_exclude_paths,
),
),
// Also exclude rel=nofollow links, as certain plugins use that on their links that perform an action.
array(
'not' => array(
'selector_matches' => 'a[rel~="nofollow"]',
),
),
// Also exclude links that are explicitly marked to opt out, either directly or via a parent element.
array(
'not' => array(
'selector_matches' => ".no-{$mode}, .no-{$mode} a",
),
),
);
// If using 'prerender', also exclude links that opt out of 'prefetch' because it's part of 'prerender'.
if ( 'prerender' === $mode ) {
$main_rule_conditions[] = array(
'not' => array(
'selector_matches' => '.no-prefetch, .no-prefetch a',
),
);
}
$speculation_rules->add_rule(
$mode,
'main',
array(
'source' => 'document',
'where' => array(
'and' => $main_rule_conditions,
),
'eagerness' => $eagerness,
)
);
/**
* Fires when speculation rules data is loaded, allowing to amend the rules.
*
* @since 6.8.0
*
* @param WP_Speculation_Rules $speculation_rules Object representing the speculation rules to use.
*/
do_action( 'wp_load_speculation_rules', $speculation_rules );
return $speculation_rules;
}
/**
* Prints the speculation rules.
*
* For browsers that do not support speculation rules yet, the `script[type="speculationrules"]` tag will be ignored.
*
* @since 6.8.0
* @access private
*/
function wp_print_speculation_rules(): void {
$speculation_rules = wp_get_speculation_rules();
if ( null === $speculation_rules ) {
return;
}
wp_print_inline_script_tag(
(string) wp_json_encode(
$speculation_rules,
JSON_HEX_TAG | JSON_UNESCAPED_SLASHES
),
array( 'type' => 'speculationrules' )
);
}