HTML API: Update Processing Instruction handling by sirreal · Pull Request #12424 · WordPress/wordpress-develop

sirreal · 2026-07-06T16:47:55Z

Handle Processing Instructions in the HTML API.

Processing instruction parsing has been updated in the HTML standard. <?processing instructions ?> were transformed into comments, but are now preserved.

See the processing instruction states in the standard.

Some doubts about parsing PI in some insertions modes came up while implementing this change. I've raised them with the standards:

Handle processing instruction tokens in head-noscript, template whatwg/html#12653
Add tests for processing instructions in templates and head noscript web-platform-tests/wpt#61120

~~See #12423 (merged here) for the test addition.~~ (landed in r62655)

Trac ticket: https://core.trac.wordpress.org/ticket/65582

Test diff vs. trunk (./vendor/bin/phpunit --group html-api-web-platform-tests)

-Tests: 1513, Assertions: 1091, Skipped: 422.
+Tests: 1637, Assertions: 1206, Skipped: 431.

(A completely new test file is enabled which accounts for both tests and skipped test numbers increasing.)

Use of AI Tools

AI assistance: Yes
Tool(s): Claude
Model(s): Fable 5
Used for: Initial implementation.

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.

…essing-instruction-parse

Claude-Session: https://claude.ai/code/session_019T4FGdVaBpVbMRcBbQPehd

…oken fixtures Claude-Session: https://claude.ai/code/session_019T4FGdVaBpVbMRcBbQPehd

Claude-Session: https://claude.ai/code/session_019T4FGdVaBpVbMRcBbQPehd

…essing-instruction-parse

web-platform-tests/wpt@a315c38

The HTML standard has added Processing Instruction parsing. The HTML API needs updates to handle PI.

…essing-instruction-parse

github-actions · 2026-07-06T16:52:26Z

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sirreal · 2026-07-06T18:00:37Z

 			case '#comment':
 			case '#funky-comment':
 			case '#presumptuous-tag':
+			case '#processing-instruction':


We'll assume this is the intention. This entire insertion mode is gone from the current version of the spec: #9298

sirreal · 2026-07-06T18:16:30Z

This adds PI handling to all the relevant insertion modes. PI handling is notably missing from two places:

This change currently follows the spec for in head noscript but inserts the token in template.

It's unclear whether these are an oversight or not. I've asked and will follow-up.

PI nodes exist and are parsed. Bogus comments are just bugos comments.

Anchor the pending data update at the end of the target and always write the same fixed form: a separating space, the data, and the `?>` closer. Reading a pending update reverses these fixed rules: skip the leading whitespace and drop the two bytes of the closer. This removes the conditional separator when setting and the conditional `?` handling when reading. Editing now collapses any whitespace run following the target to a single space and rewrites bare `>` closers as `?>`. Claude-Session: https://claude.ai/code/session_019T4FGdVaBpVbMRcBbQPehd

Every path in `set_modifiable_text()` that returns `false` now calls `_doing_it_wrong()` naming the specific reason: a comment closer in comment text, a `>` or leading whitespace in processing instruction data, a SCRIPT tag in the text of a SCRIPT element whose content type has no known escaping rules, a token that holds no settable text, and an HTML tag outside SCRIPT, STYLE, TEXTAREA, and TITLE. `wp_get_inline_script_tag()` emitted its own `_doing_it_wrong()` when the update was rejected. Drop it so the path reports once, through the message that explains the cause rather than restating the symptom. Claude-Session: https://claude.ai/code/session_01QHbzNnnDZ5p6GCFUcraKwp

sirreal · 2026-07-09T14:02:38Z

-		_doing_it_wrong(
-			__FUNCTION__,
-			__( 'Unable to set inline script data.' ),
-			'7.0.0'
-		);


This moves to WP_HTML_Tag_Processor::set_modifiable_text().

Co-authored-by: Weston Ruter <westonruter@gmail.com>

Co-authored-by: Weston Ruter <westonruter@gmail.com> Co-authored-by: Jon Surrell <sirreal@users.noreply.github.com>

westonruter

Looks great.

Just leaving some suggestions for connecting data providers with the tests they're for.

westonruter · 2026-07-09T17:48:41Z

+	}
+
+	/**
+	 * Data provider.


I've started doing this to add a bidirectional linkage.

Suggested change

* Data provider.

* Data provider for {@see self::test_no_processing_instruction_in_raw_text()}.

How helpful are you finding this? There's no reason for a data provider to be tightly coupled to a specific test or tests (even if they often are), but listing these out specifically on the data provider seems like another thing to maintain that can go stale. It's simple to search for tests using a given data provider since the data provider name will appear in any associated tests.

A simple search works, but this is a tighter coupling for easier navigation. It's a marginal improvement. Feel free to dismiss.

westonruter · 2026-07-09T17:48:59Z

+	}
+
+	/**
+	 * Data provider.


Suggested change

* Data provider.

* Data provider for {@see self::test_processing_instruction_placement()}.

westonruter · 2026-07-09T17:49:28Z

+	}
+
+	/**
+	 * Data provider.


Suggested change

* Data provider.

* Data provider for {@see self::test_sets_processing_instruction_data()}.

westonruter · 2026-07-09T17:50:04Z

+	}
+
+	/**
+	 * Data provider.


Suggested change

* Data provider.

* Data provider for {@see self::test_invalid_targets_become_comments()}.

westonruter · 2026-07-09T17:50:20Z

+	}
+
+	/**
+	 * Data provider.


Suggested change

* Data provider.

* Data provider for {@see self::test_processing_instructions()}.

westonruter · 2026-07-09T17:51:12Z

+
+	/**
+	 * Data provider.
+	 *


Suggested change

*

*

* @see self::test_serializes_processing_instructions()

* @see self::test_processing_instruction_normalization_is_idempotent()

*

The HTML specification was updated to include _processing instructions_ like `<?wp-processing-instruction ...data?>`. Implement processing instruction support in the HTML API. Developed in #12424. Props jonsurrell, dmsnell, westonruter. Fixes #65582. See #65581. git-svn-id: https://develop.svn.wordpress.org/trunk@62687 602fd350-edb4-49c9-b593-d223f7449a82

github-actions · 2026-07-10T16:46:16Z

A commit was made that fixes the Trac ticket referenced in the description of this pull request.

SVN changeset: 62687
GitHub commit: ca99fef

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.

The HTML specification was updated to include _processing instructions_ like `<?wp-processing-instruction ...data?>`. Implement processing instruction support in the HTML API. Developed in WordPress/wordpress-develop#12424. Props jonsurrell, dmsnell, westonruter. Fixes #65582. See #65581. Built from https://develop.svn.wordpress.org/trunk@62687 git-svn-id: http://core.svn.wordpress.org/trunk@61971 1a063a9b-81f0-0310-95a4-ce76da25c4cd

sirreal added 18 commits July 3, 2026 14:55

Tests: Update html5lib test data from WPT

2482ea1

Tests: Rename HTML API external suite to WPT

082b840

Tests: Update WPT workflow group name

f3c7b3e

Merge branch 'html-api-update-html5lib-wpt' into html-api/update-proc…

5646973

…essing-instruction-parse

Remove PI test skips

81d528c

Update and rename test structure

f51e56d

Update WPT dir

0faa100

Tag Processor: parse processing instructions per the HTML Standard

c2f47c8

Claude-Session: https://claude.ai/code/session_019T4FGdVaBpVbMRcBbQPehd

HTML Processor: handle and serialize processing instruction tokens

e3f60f6

Claude-Session: https://claude.ai/code/session_019T4FGdVaBpVbMRcBbQPehd

WPT harness: serialize processing instructions in tree dumps, skip br…

134041e

…oken fixtures Claude-Session: https://claude.ai/code/session_019T4FGdVaBpVbMRcBbQPehd

HTML Processor: only rewrite IMAGE to IMG for tag tokens

c4cd77d

Claude-Session: https://claude.ai/code/session_019T4FGdVaBpVbMRcBbQPehd

Merge branch 'html-api-update-html5lib-wpt' into html-api/update-proc…

d7e0898

…essing-instruction-parse

Update to latest version a315c382eac

5db5f4b

web-platform-tests/wpt@a315c38

Merge branch 'trunk' into html-api-update-html5lib-wpt

c20858c

Add necessary PI skips

f102e61

The HTML standard has added Processing Instruction parsing. The HTML API needs updates to handle PI.

Revert documentation change

f134e89

Remove unused JS files

45e1452

Merge branch 'html-api-update-html5lib-wpt' into html-api/update-proc…

f5ad313

…essing-instruction-parse

sirreal added 2 commits July 6, 2026 18:56

Simplify PI normalization comment

aaf76c2

Ensure PI data ending in ? is serialized correctly

0c7db12

sirreal commented Jul 6, 2026

View reviewed changes

sirreal added 7 commits July 6, 2026 20:18

Update PI state docs

ca3d849

Use "processing instruction" state

4fa13c8

Update PI example

d655770

Drop PI lookalike comments

24eecae

PI nodes exist and are parsed. Bogus comments are just bugos comments.

Add phpstan-return to get_token_type

d94eca0

Support set_modifiable_text on PI

b87ea5b

Add and improve test method types

860a887

sirreal added 2 commits July 9, 2026 14:13

Remove redundant tree structure doc comment

e9a1d35

Enable 3 skipped PI tests

db786e9

sirreal commented Jul 9, 2026

View reviewed changes

Comment thread tests/phpunit/tests/html-api/wpHtmlTagProcessor.php Outdated

Fix PI lookalike test

b934770

sirreal commented Jul 9, 2026

View reviewed changes

Comment thread tests/phpunit/tests/html-api/wpHtmlProcessor.php Outdated

Fix some comment examples

53e3f85

sirreal commented Jul 9, 2026

View reviewed changes

Comment thread src/wp-includes/html-api/class-wp-html-tag-processor.php Outdated

sirreal added 4 commits July 9, 2026 14:29

Note _HTML_ processing instructions are supported

268a106

Simplify comment

ceb08dc

sirreal commented Jul 9, 2026

View reviewed changes

Comment thread src/wp-includes/script-loader.php Outdated

Remove redundant comment

f9bf7f5

sirreal commented Jul 9, 2026

View reviewed changes

sirreal requested a review from westonruter July 9, 2026 14:03

sirreal added 3 commits July 9, 2026 16:04

Merge branch 'trunk' into html-api/update-processing-instruction-parse

c20cffc

Fix param name in suggestion

1d05b88

Merge branch 'trunk' into html-api/update-processing-instruction-parse

8472176

westonruter reviewed Jul 9, 2026

View reviewed changes

Remove redundant return description.

7c6f739

Co-authored-by: Weston Ruter <westonruter@gmail.com>

sirreal commented Jul 9, 2026

View reviewed changes

Comment thread src/wp-includes/html-api/class-wp-html-tag-processor.php Outdated

Apply suggestions from code review

833266d

Co-authored-by: Weston Ruter <westonruter@gmail.com> Co-authored-by: Jon Surrell <sirreal@users.noreply.github.com>

westonruter approved these changes Jul 9, 2026

View reviewed changes

sirreal added 2 commits July 9, 2026 21:25

Fix typos

4f7164b

Merge branch 'trunk' into html-api/update-processing-instruction-parse

6a00de5

github-actions Bot closed this Jul 10, 2026

sirreal deleted the html-api/update-processing-instruction-parse branch July 10, 2026 16:46

	* Data provider.
	* Data provider for {@see self::test_no_processing_instruction_in_raw_text()}.

	* Data provider.
	* Data provider for {@see self::test_processing_instruction_placement()}.

	* Data provider.
	* Data provider for {@see self::test_sets_processing_instruction_data()}.

	* Data provider.
	* Data provider for {@see self::test_invalid_targets_become_comments()}.

-	 *
+	 *
+	 * @see self::test_serializes_processing_instructions()
+	 * @see self::test_processing_instruction_normalization_is_idempotent()
+	 *

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sirreal commented Jul 6, 2026 •

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