HTML API: Ignore slash inside unquoted attribute values

[sirreal]

Summary

• Treat a trailing slash in an unquoted attribute value as part of that value.
• Prevent foreign-content elements from self-closing when no syntactic self-closing flag is present.
• Add Tag Processor and HTML Processor regressions for the MathML case.

Testing

• Focused PHPUnit coverage for unquoted trailing-slash attributes.
• HTML API PHPUnit coverage and PHPCS pass.
• codex review --base trunk.

Trac ticket: https://core.trac.wordpress.org/ticket/65372

Use of AI Tools

AI assistance: Yes
Tool(s): Codex
Model(s): GPT-5.5
Used for: PR description cleanup and code review.

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[sirreal]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.

🤖 Generated with Claude Code

[sirreal]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.

Verified the attribute-span check in has_self_closing_flag(): attributes are eagerly parsed in base_class_next_token() before this method can be called, unquoted-value spans include a trailing solidus (strcspn does not stop at /), a genuine self-closing / is never stored as an attribute, and both WP_HTML_Attribute_Token and the WP_HTML_Span duplicate-attribute entries share the same start/length semantics. The flipped expectation for <div id=test/> matches the WHATWG attribute-value-(unquoted) state, and the new tag-processor and HTML-processor tests cover the MathML regression.

🤖 Generated with Claude Code

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[sirreal]

This is an interesting one, confirmed.

<math><mi a=b/>math:mi is not self-closing, it has [a="b/"] attribute.

That should produce:

└─math:math
  └─math:mi a="b/"
    └─#text math:mi is not self-closing, it has [a="b/"] attribute.

But it produces:

└─math:math
  ├─math:mi a="b/"
  └─#text math:mi is not self-closing, it has [a="b/"] attribute.

Playground demo (WP 7.0)

I'd like to simplify the fix.