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

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Merged
westonruter 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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63 changes: 47 additions & 16 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 @@ -76,14 +76,14 @@ public function add_link( array $attributes, ?int $minimum_viewport_width, ?int
}

/**
* Get adjacent-deduplicated links.
* Prepare links by deduplicating adjacent links and adding media attributes.
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*
* When two links are identical except for their minimum/maximum widths which are also consecutive, then merge them
* together.
* together. Also, add media attributes to the links.
*
* @return array<int, Link> Links with adjacent-duplicates merged together.
* @return array<int, Link> Prepared links with adjacent-duplicates merged together and media attributes added.
*/
private function get_adjacent_deduplicated_links(): array {
private function prepare_links(): array {
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$links = $this->links;

usort(
Expand All @@ -100,7 +100,8 @@ static function ( array $a, array $b ): int {
}
);

return array_reduce(
// Deduplicating adjacent links.
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$prepared_links = array_reduce(
$links,
/**
* Reducer.
Expand All @@ -125,7 +126,7 @@ static function ( array $carry, array $link ): array {
) {
$last_link['maximum_viewport_width'] = max( $last_link['maximum_viewport_width'], $link['maximum_viewport_width'] );

// Update the last link with the new maximum viewport with.
// Update the last link with the new maximum viewport width.
$carry[ count( $carry ) - 1 ] = $last_link;
} else {
$carry[] = $link;
Expand All @@ -134,6 +135,20 @@ static function ( array $carry, array $link ): array {
},
array()
);

// Add media attributes to the deduplicated links.
foreach ( $prepared_links as &$link ) {
$media_attributes = array( 'screen' );
if ( null !== $link['minimum_viewport_width'] && $link['minimum_viewport_width'] > 0 ) {
$media_attributes[] = sprintf( '(min-width: %dpx)', $link['minimum_viewport_width'] );
}
if ( null !== $link['maximum_viewport_width'] && PHP_INT_MAX !== $link['maximum_viewport_width'] ) {
$media_attributes[] = sprintf( '(max-width: %dpx)', $link['maximum_viewport_width'] );
}
$link['attributes']['media'] = implode( ' and ', $media_attributes );
}

return $prepared_links;
}

/**
Expand All @@ -144,16 +159,7 @@ static function ( array $carry, array $link ): array {
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 );

foreach ( $this->prepare_links() as $link ) {
$link_tag = '<link data-od-added-tag rel="preload"';
foreach ( $link['attributes'] as $name => $value ) {
$link_tag .= sprintf( ' %s="%s"', $name, esc_attr( $value ) );
Expand All @@ -166,6 +172,31 @@ 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->prepare_links() as $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.
*
Expand Down
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() );
}

Expand Down