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Script Loader: Drop obsolete pr attribute and build resource hint and preload tags with the HTML API #15331

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Script Loader: Drop obsolete pr attribute and build resource hint and preload tags with the HTML API #15331

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e7764ce
Stop printing the obsolete pr attribute in resource hints
westonruter Nov 1, 2026
c413f61
Map allowed resource hint attributes to whether they can be valueless
westonruter Nov 1, 2026
dc433d7
Allow more spec-defined link attributes on resource hints
westonruter Nov 1, 2026
db9db3f
Tag the resource hint attribute tests with their ticket
westonruter Nov 1, 2026
79b7c15
Compare resource hint markup with assertEqualHTML
westonruter Nov 2, 2026
33ea505
Link the boolean attributes data provider to its test
westonruter Nov 2, 2026
2addb9a
Build resource hint tags with the HTML Tag Processor
westonruter Nov 4, 2026
4d1a8dd
Merge branch 'trunk' of https://github.com/WordPress/wordpress-develo…
westonruter Nov 4, 2026
016be5f
Build preload tags with the HTML Tag Processor
westonruter Nov 4, 2026
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163 changes: 119 additions & 44 deletions src/wp-includes/general-template.php
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Original file line number Diff line number Diff line change
Expand Up @@ -3945,6 +3945,27 @@ function wp_resource_hints() {
'prerender' => array(),
);

/*
* Attributes which may be printed on a resource hint, mapped to whether the
* attribute may be printed without a value when it is supplied as `true`.
*
* Other attributes of the link element are omitted because the HTML spec only
* allows them with other link types: blocking, color, disabled, imagesizes,
* imagesrcset, integrity, and sizes.
*/
$allowed_attributes = array(
'as' => false,
'crossorigin' => true,
'fetchpriority' => false,
'href' => false,
'hreflang' => false,
'media' => false,
'referrerpolicy' => false,
'rel' => false,
'title' => false,
'type' => false,
);

foreach ( $hints as $relation_type => $urls ) {
$unique_urls = array();

Expand All @@ -3954,19 +3975,31 @@ function wp_resource_hints() {
* @since 4.6.0
* @since 4.7.0 The `$urls` parameter accepts arrays of specific HTML attributes
* as its child elements.
* @since 7.3.0 The obsolete `pr` attribute is no longer printed. The `crossorigin`
* attribute may be `true` to print it without a value. Added the
* `fetchpriority`, `hreflang`, `media`, `referrerpolicy`, and `title`
* attributes.
*
* @param array $urls {
* Array of resources and their attributes, or URLs to print for resource hints.
*
* @type array|string ...$0 {
* Array of resource attributes, or a URL string.
* Array of resource attributes, or a URL string. A valueless attribute
* may also be supplied as a list item, as in `array( 'crossorigin' )`.
*
* @type string $href URL to include in resource hints. Required.
* @type string $as How the browser should treat the resource
* (`script`, `style`, `image`, `document`, etc).
* @type string $crossorigin Indicates the CORS policy of the specified resource.
* @type float $pr Expected probability that the resource hint will be used.
* @type string $type Type of the resource (`text/html`, `text/css`, etc).
* @type string $href URL to include in resource hints. Required.
* @type string $as How the browser should treat the resource
* (`script`, `style`, `image`, `document`, etc).
* @type string|bool $crossorigin Indicates the CORS policy of the specified resource.
* When `true`, it is printed without a value, which
* is equivalent to `anonymous`.
* @type string $fetchpriority Priority of the fetch relative to other resources
* (`high`, `low`, or `auto`).
* @type string $hreflang Language of the resource.
* @type string $media Media query the resource applies to.
* @type string $referrerpolicy Referrer policy for the fetch.
* @type string $title Title of the resource hint.
* @type string $type Type of the resource (`text/html`, `text/css`, etc).
* }
* }
* @param string $relation_type The relation type the URLs are printed for. One of
Expand Down Expand Up @@ -4018,28 +4051,37 @@ function wp_resource_hints() {
}

foreach ( $unique_urls as $atts ) {
$html = '';
$processor = new WP_HTML_Tag_Processor( '<link>' );
$processor->next_tag();

foreach ( $atts as $attr => $value ) {
if ( ! is_scalar( $value )
|| ( ! in_array( $attr, array( 'as', 'crossorigin', 'href', 'pr', 'rel', 'type' ), true ) && ! is_numeric( $attr ) )
) {
// A list item supplies a valueless attribute, as in `array( 'crossorigin', 'href' => … )`.
if ( is_int( $attr ) ) {
if ( ! is_string( $value ) ) {
continue;
}
$attr = $value;
$value = true;
}

if ( ! isset( $allowed_attributes[ $attr ] ) ) {
continue;
}

$value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );

if ( ! is_string( $attr ) ) {
$html .= " $value";
if ( is_bool( $value ) ) {
if ( ! $allowed_attributes[ $attr ] ) {
continue;
}
} elseif ( is_scalar( $value ) ) {
$value = (string) $value;
} else {
$html .= " $attr='$value'";
continue;
}
}

$html = trim( $html );
$processor->set_attribute( $attr, $value );
}

echo "<link $html />\n";
echo $processor->get_updated_html() . "\n";
}
}
}
Expand All @@ -4066,23 +4108,28 @@ function wp_preload_resources() {
*
* @since 6.1.0
* @since 6.6.0 Added the `$fetchpriority` attribute.
* @since 7.3.0 The `crossorigin` attribute may be `true` to print it without a value.
* List items other than `crossorigin` are no longer printed.
*
* @param array $preload_resources {
* Array of resources and their attributes, or URLs to print for resource preloads.
*
* @type array ...$0 {
* Array of resource attributes.
*
* @type string $href URL to include in resource preloads. May be omitted
* for an image preloaded by its `$imagesrcset`.
* @type string $as How the browser should treat the resource
* (`script`, `style`, `image`, `document`, etc).
* @type string $crossorigin Indicates the CORS policy of the specified resource.
* @type string $type Type of the resource (`text/html`, `text/css`, etc).
* @type string $media Accepts media types or media queries. Allows responsive preloading.
* @type string $imagesizes Responsive source size to the source Set.
* @type string $imagesrcset Responsive image sources to the source set.
* @type string $fetchpriority Fetchpriority value for the resource.
* Array of resource attributes. A valueless attribute may also be supplied
* as a list item, as in `array( 'crossorigin' )`.
*
* @type string $href URL to include in resource preloads. May be omitted
* for an image preloaded by its `$imagesrcset`.
* @type string $as How the browser should treat the resource
* (`script`, `style`, `image`, `document`, etc).
* @type string|bool $crossorigin Indicates the CORS policy of the specified resource.
* When `true`, it is printed without a value, which
* is equivalent to `anonymous`.
* @type string $type Type of the resource (`text/html`, `text/css`, etc).
* @type string $media Accepts media types or media queries. Allows responsive preloading.
* @type string $imagesizes Responsive source size to the source Set.
* @type string $imagesrcset Responsive image sources to the source set.
* @type string $fetchpriority Fetchpriority value for the resource.
* }
* }
*/
Expand Down Expand Up @@ -4118,18 +4165,49 @@ function wp_preload_resources() {
}
}

/*
* Attributes which may be printed on a preload, mapped to whether the
* attribute may be printed without a value when it is supplied as `true`.
*/
$allowed_attributes = array(
'as' => false,
'crossorigin' => true,
'fetchpriority' => false,
'href' => false,
'imagesizes' => false,
'imagesrcset' => false,
'media' => false,
'type' => false,
);

// Build and output the HTML for each unique resource.
foreach ( $unique_resources as $unique_resource ) {
$html = '';
$processor = new WP_HTML_Tag_Processor( '<link>' );
$processor->next_tag();
$processor->set_attribute( 'rel', 'preload' );

foreach ( $unique_resource as $resource_key => $resource_value ) {
if ( ! is_scalar( $resource_value ) ) {
continue;
// A list item supplies a valueless attribute, as in `array( 'crossorigin', 'href' => … )`.
if ( is_int( $resource_key ) ) {
if ( ! is_string( $resource_value ) ) {
continue;
}
$resource_key = $resource_value;
$resource_value = true;
}

// Ignore non-supported attributes.
$non_supported_attributes = array( 'as', 'crossorigin', 'href', 'imagesrcset', 'imagesizes', 'type', 'media', 'fetchpriority' );
if ( ! in_array( $resource_key, $non_supported_attributes, true ) && ! is_numeric( $resource_key ) ) {
if ( ! isset( $allowed_attributes[ $resource_key ] ) ) {
continue;
}

if ( is_bool( $resource_value ) ) {
if ( ! $allowed_attributes[ $resource_key ] ) {
continue;
}
} elseif ( is_scalar( $resource_value ) ) {
$resource_value = (string) $resource_value;
} else {
continue;
}

Expand All @@ -4145,17 +4223,14 @@ function wp_preload_resources() {
continue;
}

$resource_value = ( 'href' === $resource_key ) ? esc_url( $resource_value, array( 'http', 'https' ) ) : esc_attr( $resource_value );

if ( ! is_string( $resource_key ) ) {
$html .= " $resource_value";
} else {
$html .= " $resource_key='$resource_value'";
if ( 'href' === $resource_key && is_string( $resource_value ) ) {
$resource_value = sanitize_url( $resource_value, array( 'http', 'https' ) );
}

$processor->set_attribute( $resource_key, $resource_value );
}
$html = trim( $html );

printf( "<link rel='preload' %s />\n", $html );
echo $processor->get_updated_html() . "\n";
}
}

Expand Down
95 changes: 92 additions & 3 deletions tests/phpunit/tests/general/wpPreloadResources.php
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Original file line number Diff line number Diff line change
Expand Up @@ -12,8 +12,11 @@ class Tests_General_wpPreloadResources extends WP_UnitTestCase {
* @dataProvider data_preload_resources
*
* @ticket 42438
*
* @param string $expected Expected markup.
* @param array<int, array<int|string, mixed>> $preload_resources Resources to preload.
*/
public function test_preload_resources( $expected, $preload_resources ) {
public function test_preload_resources( string $expected, array $preload_resources ) {
$callback = static function () use ( $preload_resources ) {
return $preload_resources;
};
Expand All @@ -22,11 +25,11 @@ public function test_preload_resources( $expected, $preload_resources ) {
$actual = get_echo( 'wp_preload_resources' );
remove_filter( 'wp_preload_resources', $callback );

$this->assertSame( $expected, $actual );
$this->assertEqualHTML( $expected, $actual );
}

/**
* Test provider for all preload link possible combinations.
* Data provider for {@see self::test_preload_resources()}.
*
* @return array[]
*/
Expand Down Expand Up @@ -286,4 +289,90 @@ public static function data_preload_resources() {
),
);
}

/**
* Tests that boolean attribute values and list items are only printed when valueless.
*
* @ticket 66435
*
* @dataProvider data_boolean_attributes
*
* @param string $expected Expected markup.
* @param array<int|string, mixed> $preload_resource Resource to preload.
*/
public function test_boolean_attributes( string $expected, array $preload_resource ) {
add_filter(
'wp_preload_resources',
static function () use ( $preload_resource ): array {
return array( $preload_resource );
}
);

$this->assertEqualHTML( $expected, get_echo( 'wp_preload_resources' ) );
}

/**
* Data provider for {@see self::test_boolean_attributes()}.
*
* @return array<non-falsy-string, array{ expected: string, preload_resource: array<int|string, mixed> }>
*/
public static function data_boolean_attributes(): array {
return array(
'crossorigin true' => array(
'expected' => "<link rel='preload' href='https://example.com/font.woff2' as='font' crossorigin />\n",
'preload_resource' => array(
'href' => 'https://example.com/font.woff2',
'as' => 'font',
'crossorigin' => true,
),
),
'crossorigin false' => array(
'expected' => "<link rel='preload' href='https://example.com/font.woff2' as='font' />\n",
'preload_resource' => array(
'href' => 'https://example.com/font.woff2',
'as' => 'font',
'crossorigin' => false,
),
),
'non-boolean attribute true' => array(
'expected' => "<link rel='preload' href='https://example.com/main.js' as='script' />\n",
'preload_resource' => array(
'href' => 'https://example.com/main.js',
'as' => 'script',
'type' => true,
),
),
'unsupported list item' => array(
'expected' => "<link rel='preload' href='https://example.com/main.js' as='script' />\n",
'preload_resource' => array(
'href' => 'https://example.com/main.js',
'as' => 'script',
'async',
),
),
'non-string list item' => array(
'expected' => "<link rel='preload' href='https://example.com/main.js' as='script' />\n",
'preload_resource' => array(
'href' => 'https://example.com/main.js',
'as' => 'script',
true,
),
),
'escaped attribute value' => array(
'expected' => "<link rel='preload' href='https://example.com/style.css' as='style' media='screen and (min-width: 600px)&quot; onload=&quot;alert(1)' />\n",
'preload_resource' => array(
'href' => 'https://example.com/style.css',
'as' => 'style',
'media' => 'screen and (min-width: 600px)" onload="alert(1)',
),
),
'unsafe href protocol removed' => array(
'expected' => "<link rel='preload' href='' as='script' />\n",
'preload_resource' => array(
'href' => 'javascript:alert(1)',
'as' => 'script',
),
),
);
}
}
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