HTML API: Remove all duplicate copies of an attribute when removing

[dmsnell]

Description

Trac ticket #58119

When encountering an HTML tag with duplicate copies of an attribute the tag processor ignores the duplicate values, according to the specification. However, when removing an attribute it must remove all copies of that attribute lest one of the duplicates becomes the primary and it appears as if no attributes were removed.

In this patch we're adding tests that will be used to ensure that all attribute copies are removed from a tag when one is request to be removed.

Before

$p = new WP_HTML_Tag_Processor( '<br id=one id="two" id='three' id>' );
$p->next_tag();
$p->remove_attribute( 'id' );
$p->get_updated_html();
// <br id="two" id='three' id>

After

$p = new WP_HTML_Tag_Processor( '<br id=one id="two" id='three' id>' );
$p->next_tag();
$p->remove_attribute( 'id' );
$p->get_updated_html();
// <br>

Previously we have been overlooking duplicate attributes since they don't have an impact on what parses into the DOM. However, as one unit test affirmed (asserting the presence of the bug in the tag processor) when removing an attribute where duplicates exist this meant we ended up changing the value of an attribute instead of removing it.

In this patch we're tracking the text spans of the parsed duplicate attributes so that if we attempt to remove them then we'll have the appropriate information necessary to do so. When an attribute isn't removed we'll simply forget about the tracked duplicates. This involves some overhead for normal operation when in fact there are duplicate attributes on a tag, but that overhead is minimal in the form of integer pairs of indices for each duplicated attribute.

cc: @adamziel @ockham

[adamziel]

The logic LGTM @dmsnell, thank you! I left a few nitpicks about formatting, but that's it.

[ockham]

Not sure I'm reading this correctly, but allocating one empty array (per tag processor) doesn't seem terribly expensive?

[dmsnell]

I agree. doesn't seem that it's any clearer though to be more expensive than less does it?

[ockham]

Maybe ever so slightly clearer, but fine to keep as-is 👍

[dmsnell]

at some point I'll try and make a reasonable benchmark. until then I'll leave it at avoiding allocation. I'm afraid of allocation

[ockham]

Suggested change

	'First attribute (when duplicates exist) was not removed'
	'First attribute (and duplicates) were not removed'

maybe?

[dmsnell]

I rewrote the test to try and be more specific that this one test is solely about removing the first instance of the attribute, as when updating attributes it's the first that matters. Previously this test simply locked-in the behavior that the first was the one to go.

[ockham]

Looking good. Left a few minor notes (mostly non-blocking).

Planning to land this (with updated @since PHPDocs) later tonight, so we have it ready for both 6.4 and 6.3.2.

[ockham]

👍

[ockham]

Committed to Core trunk in https://core.trac.wordpress.org/changeset/56684.

[ockham]

Committed to Core's 6.3 branch in https://core.trac.wordpress.org/changeset/56685.