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Script Loader: Drop obsolete pr attribute and build resource hint and preload tags with the HTML API - #15331
Script Loader: Drop obsolete pr attribute and build resource hint and preload tags with the HTML API#15331westonruter wants to merge 15 commits into
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The `pr` (hint probability) attribute was only ever part of the W3C Resource Hints working drafts. No browser implemented it, and it was removed from that spec in 2018. The HTML Living Standard, which now defines resource hints, has no such attribute on `<link>`, so printing it only produces invalid markup. Remove `pr` from the allowed attributes and from the `wp_resource_hints` filter documentation. The test keeps passing `pr` to assert that it is now dropped. Co-Authored-By: Claude Opus 5.5 (medium effort) <noreply@anthropic.com> Claude-Code-Session-Id: 7f6d7eea-e6bc-4b05-9181-cad948a21000
Move the inline attribute allowlist in `wp_resource_hints()` up into an `$allowed_attributes` map, keyed by attribute name, whose value says whether the attribute may be printed without a value. Of the currently allowed attributes, only `crossorigin` can be. This tightens how valueless attributes are handled: * `'crossorigin' => true` now prints a bare `crossorigin` instead of `crossorigin='1'`, and `false` omits it instead of printing `crossorigin=''`. * A list item, as in `array( 'crossorigin', 'href' => … )`, is now printed only when it names an allowed attribute which may be valueless. Previously any string list item was printed as a bare attribute, which let arbitrary attribute names past the allowlist. * `true` or `false` given for an attribute that requires a value is skipped rather than printed as `'1'` or `''`. Co-Authored-By: Claude Opus 5.5 (medium effort) <noreply@anthropic.com> Claude-Code-Session-Id: 7f6d7eea-e6bc-4b05-9181-cad948a21000
Add `fetchpriority`, `hreflang`, `media`, `referrerpolicy`, and `title` to the attributes `wp_resource_hints()` prints. They are the remaining attributes of the HTML link element which the spec allows with the dns-prefetch, preconnect, prefetch, and prerender link types. Of these, `fetchpriority` is the closest successor to the removed `pr` attribute, as it lets a hint signal how important its fetch is. The other link attributes stay disallowed, since the spec only permits them with other link types: `blocking` (stylesheet, expect), `color` (mask-icon), `disabled` (stylesheet), `imagesizes` and `imagesrcset` (preload of an image), `integrity` (stylesheet, preload, modulepreload), and `sizes` (icons). Co-Authored-By: Claude Opus 5.5 (medium effort) <noreply@anthropic.com> Claude-Code-Session-Id: 7f6d7eea-e6bc-4b05-9181-cad948a21000
Co-Authored-By: Claude Opus 5.5 (medium effort) <noreply@anthropic.com> Claude-Code-Session-Id: 7f6d7eea-e6bc-4b05-9181-cad948a21000
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🤖 Comment by Claude Opus 5.5 (medium effort) A Veloria search of the plugin and theme directories found no code using Details
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The resource hint tests compared the printed `<link>` tags as exact strings, so they also asserted incidental details such as attribute order and quoting style. Use `assertEqualHTML()` so they assert only that the markup is equivalent HTML. Co-Authored-By: Claude Opus 5.5 (medium effort) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Tnky3GYbMqxozZLnF3PvQp Claude-Code-Session-Id: 7f6d7eea-e6bc-4b05-9181-cad948a21000
Co-Authored-By: Claude Opus 5.5 (medium effort) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Tnky3GYbMqxozZLnF3PvQp Claude-Code-Session-Id: 7f6d7eea-e6bc-4b05-9181-cad948a21000
Constructing the `<link>` markup by hand meant escaping each value and printing valueless attributes manually. `WP_HTML_Tag_Processor::set_attribute()` handles both: it escapes values (running URL attributes like `href` through `esc_url()`), and it prints `true` as a bare attribute. The allowlist still decides which attributes may be printed and which may be valueless. Co-Authored-By: Claude Opus 5.5 (medium effort) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Tnky3GYbMqxozZLnF3PvQp Claude-Code-Session-Id: 7f6d7eea-e6bc-4b05-9181-cad948a21000
…into fix/resource-hints-pr-attribute
Like `wp_resource_hints()`, `wp_preload_resources()` assembled its `<link>` markup by hand. Build it with `WP_HTML_Tag_Processor` instead, so attribute values are escaped and valueless attributes are printed by `set_attribute()`. The `href` is still limited to the `http` and `https` protocols. The attribute allowlist becomes an `$allowed_attributes` map recording whether each attribute may be valueless, as in `wp_resource_hints()`. This fixes two cases: * `'crossorigin' => true` printed `crossorigin='1'`, and now prints a bare `crossorigin`. * Any list item was printed as a bare attribute, unchecked against the allowlist. Now only `crossorigin` is. The tests now compare markup with `assertEqualHTML()` and cover these cases. Co-Authored-By: Claude Opus 5.5 (medium effort) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Tnky3GYbMqxozZLnF3PvQp Claude-Code-Session-Id: 7f6d7eea-e6bc-4b05-9181-cad948a21000
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sirreal
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I love to see this!
I've left some notes, nothing major. This seems ready to merge at your discretion.
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| $html = trim( $html ); | ||
| $processor->set_attribute( $attr, $value ); |
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This is a small behavioral change here. Before, duplicate attributes were all appended. According to HTML, the first one wins. The tag processor will not add duplicate attributes, it sets the last set_attribute() making this "last one wins".
To preserve the "first in the array wins" behavior, the script tag handles it like this:
wordpress-develop/src/wp-includes/script-loader.php
Lines 3380 to 3399 in 7516662
It would be good to add a few tests for the duplicate attribute behaviors, especially like [ 'crossorigin', 'crossorigin' => 'value' ].
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🤖 Comment by Claude Opus 5.5 (medium effort)
Fixed in dde14f8. An attribute the tag already has is now skipped, so the first one wins, as in wp_get_inline_script_tag(). Tests were added for [ 'crossorigin', 'crossorigin' => 'use-credentials' ], the reverse order, and a repeated list item, in both functions.
| * imagesrcset, integrity, and sizes. | ||
| */ | ||
| $allowed_attributes = array( | ||
| 'as' => false, |
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I find the structure of this data and the description confusing. As a local value, it shouldn't be a big deal but I think some refinement here would be helpful.
Here's what I understand:
- key is present: attribute is allowed
- value: true indicates the attribute may appear as a boolean (valueless) attribute.
The
asattribute specifies…
The attribute must be specified onlinkelements that have arelattribute that contains thepreloadkeyword…
It may be specified onlinkelements that have arelattribute that contains themodulepreloadkeyword…
For other link elements, it must not be specified.
So it's required by the spec in some cases, and prohibited in others.
I'm happy to leave that out of scope, but it's something to consider. I'm not sure what the implications are, this could probably remove as in some cases where it must not be specified, but where it's required I'm less sure what would be a good failure mode.
Looking at the specification for rel, I think a get_attribute_as_token_list() or attribute_token_list_contains( 'rel', 'preload' ): bool would be useful for this type of thing.
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🤖 Comment by Claude Opus 5.5 (medium effort)
The comment was reworded in 3ece593: a key's presence is what allows an attribute, and a true value lets it also be printed as a boolean attribute.
Restricting as is left out of scope. It was already allowed on resource hints before this PR, and plugins may pass it with prefetch, so dropping it would be a separate behavior change.
A token-list helper for rel would be a nice HTML API addition, but it belongs on its own ticket.
| $html .= " $resource_value"; | ||
| } else { | ||
| $html .= " $resource_key='$resource_value'"; | ||
| if ( 'href' === $resource_key && is_string( $resource_value ) ) { |
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The allow list makes case sensitivity irrelevant (this is correct).
The is_string() is redundant at this point, isn't it? Above, scalars are coerced to strings and non-scalars continue the loop iteration.
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🤖 Comment by Claude Opus 5.5 (medium effort)
Yes, it was redundant. It was removed in 2743a24, which sanitizes the href while collecting unique resources instead. A non-string or unsafe href is now treated as missing, so the resource falls back to its imagesrcset or is skipped, rather than being printed with an empty href.
| $processor = new WP_HTML_Tag_Processor( '<link>' ); | ||
| $processor->next_tag(); | ||
| $processor->set_attribute( 'rel', 'preload' ); |
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Just review notes, no change requests.
If rel were allowed, it would need to be set at the end to ensure its value is applied. That's not an issue now.
As a static and pretty trivial attribute that can't be changed in the loop below, we could include rel in the initial HTML: <link rel="preload">.
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🤖 Comment by Claude Opus 5.5 (medium effort)
Done in 8c189b8: the processor now starts from <link rel="preload">.
| * attribute may be printed without a value when it is supplied as `true`. | ||
| */ | ||
| $allowed_attributes = array( | ||
| 'as' => false, |
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My other notes apply to as here as well.
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🤖 Comment by Claude Opus 5.5 (medium effort)
For preloads, as is required by the spec rather than prohibited, so it stays in this allowlist. Enforcing its presence, and deciding what to do when it is missing, is left out of scope like the resource hints note.
| $resource_value = sanitize_url( $resource_value, array( 'http', 'https' ) ); | ||
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| $processor->set_attribute( $resource_key, $resource_value ); |
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Same notes as above where setting without a get_attribute( $resource_key ) === null check first is a behavioral change from "first in the list wins" to "last in the list wins".
An early !== null check can continue the loop early and skip some processing in those cases.
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🤖 Comment by Claude Opus 5.5 (medium effort)
Covered by the same change in dde14f8. The get_attribute() check is made together with the allowlist check, so a duplicate skips the rest of the loop body.
| * | ||
| * @return array<string, array{ hint: array<int|string, mixed>, expected: string }> | ||
| */ | ||
| public function data_boolean_attributes(): array { |
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| public function data_boolean_attributes(): array { | |
| public static function data_boolean_attributes(): array { |
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🤖 Comment by Claude Opus 5.5 (medium effort)
Applied in 0ef0d79, along with non-falsy-string keys in the return type.
| * @since 4.6.0 | ||
| * @since 4.7.0 The `$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` |
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The Trac ticket says milestone: 7.2 ... was this intended for the 7.2 release? I assume not, since we're so close to 7.2 right now, but I wanted to make sure, just in case.
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Good catch. I have re-milestoned for 7.3 in any case, as I'm running out of time.
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🤖 Comment by Claude Opus 5.5 (medium effort)
No, this is not meant for 7.2. The @since 7.3.0 tags reflect the intended release, so the ticket's milestone should be moved to match.
A preload whose `href` was not a string, or whose protocol was stripped by sanitization (such as `javascript:`), was still printed, either with an empty `href` or with none at all. Such a tag preloads nothing. Sanitize the `href` while collecting unique resources instead of while printing them. An unusable `href` is then treated as absent: the resource falls back to its `imagesrcset` when it is an image, and is skipped otherwise. The sanitized URL also becomes the key for removing duplicates, so two spellings of the same URL yield one preload. A non-string `imagesrcset` is likewise rejected instead of being used as an array key. Co-Authored-By: Claude Opus 5.5 (medium effort) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Tnky3GYbMqxozZLnF3PvQp Claude-Code-Session-Id: 7f6d7eea-e6bc-4b05-9181-cad948a21000
The `@since 7.3.0` note did not mention that list items other than `crossorigin` are no longer printed as valueless attributes. The note on `wp_preload_resources` already says so. Co-Authored-By: Claude Opus 5.5 (medium effort) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Tnky3GYbMqxozZLnF3PvQp Claude-Code-Session-Id: 7f6d7eea-e6bc-4b05-9181-cad948a21000
Newer PHPUnit versions deprecate and then reject non-static data providers, and the matching provider for the preload tests is already static. Also type its keys as `non-falsy-string`. Co-Authored-By: Claude Opus 5.5 (medium effort) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Tnky3GYbMqxozZLnF3PvQp Claude-Code-Session-Id: 7f6d7eea-e6bc-4b05-9181-cad948a21000
An attribute can be supplied twice, as in `array( 'crossorigin', 'crossorigin' => 'use-credentials' )`. The hand-built markup printed both, and HTML applies the first. With the HTML API, each `set_attribute()` call overwrites the previous one, so the last would win. Skip an attribute the tag already has, as `wp_get_inline_script_tag()` does, so the first one still wins. Co-Authored-By: Claude Opus 5.5 (medium effort) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Tnky3GYbMqxozZLnF3PvQp Claude-Code-Session-Id: 7f6d7eea-e6bc-4b05-9181-cad948a21000
The `rel` is fixed and cannot be supplied by the filter, so include it in the initial HTML instead of setting it through the HTML API. Co-Authored-By: Claude Opus 5.5 (medium effort) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Tnky3GYbMqxozZLnF3PvQp Claude-Code-Session-Id: 7f6d7eea-e6bc-4b05-9181-cad948a21000
Spell out that a key's presence is what allows an attribute, and that a `true` value allows it to also be printed as a boolean attribute. Co-Authored-By: Claude Opus 5.5 (medium effort) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Tnky3GYbMqxozZLnF3PvQp Claude-Code-Session-Id: 7f6d7eea-e6bc-4b05-9181-cad948a21000
The
pr("hint probability") attribute allowed bywp_resource_hints()since r38826 was only ever part of the W3C Resource Hints working drafts. No browser implemented it, and it was removed from that spec in w3c/resource-hints#76. The HTML Living Standard, which now defines resource hints, has no such attribute on<link>, so printing it only produces invalid markup.This PR:
prand removes it from thewp_resource_hintsfilter documentation.$allowed_attributesmap from each attribute name to whether it may be printed without a value. Onlycrossorigincan be valueless.fetchpriority,hreflang,media,referrerpolicy, andtitle, the remaining<link>attributes the spec permits withdns-prefetch,preconnect,prefetch, andprerender. Of these,fetchprioritymost closely fills the roleprwas meant to. The other<link>attributes stay disallowed because the spec restricts them to other link types:blocking,color,disabled,imagesizes,imagesrcset,integrity, andsizes.$allowed_attributesmap approach towp_preload_resources(), which shared the same hand-built markup and the same valueless attribute handling.<link>tags in both functions withWP_HTML_Tag_Processorinstead of concatenating strings, soset_attribute()escapes the values (runninghrefthroughesc_url()) and printstrueas a bare attribute. The preloadhrefis still limited to thehttpandhttpsprotocols.Behavior changes for valueless attributes, in both
wp_resource_hints()andwp_preload_resources():'crossorigin' => trueprints a barecrossorigininstead ofcrossorigin='1', andfalseomits it instead of printingcrossorigin=''.array( 'crossorigin', 'href' => … ), is printed only when it names an allowed attribute that may be valueless. Previously any string list item was printed as a bare attribute, which let arbitrary attribute names bypass the allowlist.trueorfalsesupplied for an attribute that requires a value is skipped instead of being printed as'1'or''.Markup changes from using the HTML API:
/>. For example,<link rel='dns-prefetch' href='//wordpress.org' />is now printed as<link rel="dns-prefetch" href="//wordpress.org">. The tests now compare markup withassertEqualHTML(), so they are not tied to either serialization.&in a value is encoded, whereasesc_attr()left existing character references alone. A value that was already HTML-escaped by the caller, such asTom & Jerry, is now double-encoded.Trac ticket: https://core.trac.wordpress.org/ticket/66435
Use of AI Tools
AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 5.5 (medium effort)
Used for: Researching the status of the
prattribute and the<link>attributes in the HTML spec, implementing the changes and tests, and drafting the Trac ticket and this description, under the direction of the author, who reviewed the result.This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.