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Send preload links via HTTP Link headers in addition to LINK tags #1323

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merged 10 commits into from
Jul 8, 2024
Merged

Send preload links via HTTP Link headers in addition to LINK tags #1323

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7fdc181
Add support for sending preload links via HTTP headers
AhmarZaidi Jun 28, 2024
1e3a242
PR Changes
AhmarZaidi Jul 2, 2024
e7103c6
Merge branch 'trunk' into preload-links
AhmarZaidi Jul 2, 2024
b36959a
Prepare links
AhmarZaidi Jul 3, 2024
c3acee8
PR Changes
AhmarZaidi Jul 4, 2024
9a47aae
Add test for http link response headers
AhmarZaidi Jul 7, 2024
f2fbe38
Remove unnecessary global namespace backslash
westonruter Jul 8, 2024
d1cd8d4
Escape quoted strings according to RFC 9110
westonruter Jul 8, 2024
25299f7
Merge branch 'trunk' into preload-links
westonruter Jul 8, 2024
f4ab19a
Use array_map() instead of reference
westonruter Jul 8, 2024
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57 changes: 49 additions & 8 deletions plugins/optimization-detective/class-od-preload-link-collection.php
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,27 @@ static function ( array $carry, array $link ): array {
);
}

/**
* Adds media features to the links.
*
* @phpstan-param Link $link
* @param array $link Link array.
* @phpstan-return Link
* @return array Link array with media features added.
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*/
private function add_media_features( array $link ): array {
$media_features = array( 'screen' );
if ( null !== $link['minimum_viewport_width'] && $link['minimum_viewport_width'] > 0 ) {
$media_features[] = sprintf( '(min-width: %dpx)', $link['minimum_viewport_width'] );
}
if ( null !== $link['maximum_viewport_width'] && PHP_INT_MAX !== $link['maximum_viewport_width'] ) {
$media_features[] = sprintf( '(max-width: %dpx)', $link['maximum_viewport_width'] );
}
$link['attributes']['media'] = implode( ' and ', $media_features );

return (array) $link;
}
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/**
* Gets the HTML for the link tags.
*
Expand All @@ -145,14 +166,7 @@ public function get_html(): string {
$link_tags = array();

foreach ( $this->get_adjacent_deduplicated_links() as $link ) {
$media_features = array( 'screen' );
if ( null !== $link['minimum_viewport_width'] && $link['minimum_viewport_width'] > 0 ) {
$media_features[] = sprintf( '(min-width: %dpx)', $link['minimum_viewport_width'] );
}
if ( null !== $link['maximum_viewport_width'] && PHP_INT_MAX !== $link['maximum_viewport_width'] ) {
$media_features[] = sprintf( '(max-width: %dpx)', $link['maximum_viewport_width'] );
}
$link['attributes']['media'] = implode( ' and ', $media_features );
$link = $this->add_media_features( (array) $link );
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$link_tag = '<link data-od-added-tag rel="preload"';
foreach ( $link['attributes'] as $name => $value ) {
Expand All @@ -166,6 +180,33 @@ public function get_html(): string {
return implode( '', $link_tags );
}

/**
* Constructs the Link HTTP response header.
*
* @return string|null Link HTTP response header, or null if there are none.
*/
public function get_response_header(): ?string {
$link_headers = array();

foreach ( $this->get_adjacent_deduplicated_links() as $link ) {
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$link = $this->add_media_features( (array) $link );

$link_header = '<' . esc_url_raw( $link['attributes']['href'] ?? '' ) . '>; rel="preload"';
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foreach ( $link['attributes'] as $name => $value ) {
if ( 'href' !== $name ) {
$link_header .= sprintf( '; %s="%s"', $name, rawurlencode( $value ) );
}
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}

$link_headers[] = $link_header;
}
if ( count( $link_headers ) === 0 ) {
return null;
}

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return 'Link: ' . implode( ', ', $link_headers );
}

/**
* Counts the links.
*
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6 changes: 5 additions & 1 deletion plugins/optimization-detective/optimization.php
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Original file line number Diff line number Diff line change
Expand Up @@ -189,8 +189,12 @@ function od_optimize_template_output_buffer( string $buffer ): string {
$generator->next();
}

// Inject any preload links at the end of the HEAD.
// Send any preload links in a Link response header and in a LINK tag injected at the end of the HEAD.
if ( count( $preload_links ) > 0 ) {
$response_header_links = $preload_links->get_response_header();
if ( ! is_null( $response_header_links ) && ! headers_sent() ) {
header( $response_header_links, false );
}
$walker->append_head_html( $preload_links->get_html() );
}

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