HTML is a kind of short-hand for a DOM structure. This means that there are
many cases in HTML where an element's opening tag or closing tag is missing (or
both). This is because many of the parsing rules imply creating elements in the
DOM which may not exist in the text of the HTML.
The HTML Processor, being the higher-level counterpart to the Tag Processor, is
already aware of these nodes, but since it's inception has not paused on them
when scanning through a document. Instead, these are visible when pausing on a
child of such an element, but otherwise not seen.
In this patch the HTML Processor starts exposing those implicitly-created nodes,
including opening tags, and closing tags, that aren't foudn in the text content
of the HTML input document.
Previously, the sequence of matched tokens when scanning with
`WP_HTML_Processor::next_token()` would depend on how the HTML document was written,
but with this patch, all semantically equal HTML documents will parse and scan in
the same exact manner, presenting an idealized or "perfect" view of the document
the same way as would occur when traversing a DOM in a browser.
Developed in https://github.com/WordPress/wordpress-develop/pull/6348
Discussed in https://core.trac.wordpress.org/ticket/61348
Props audrasjb, dmsnell, gziolo, jonsurrell.
Fixes#61348.
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Adds support for the following HTML elements to the HTML Processor:
- LI, OL, UL.
- DD, DL, DT.
Previously, these elements were not supported and the HTML Processor would bail when encountering them.
With this patch it will proceed to parse an HTML document when encountering those tags as long as other normal conditions don't cause it to bail (such as complicated format reconstruction).
Props audrasjb, jonsurrell, bernhard-reiter.
Fixes#60215.
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Previously these have been unsupported, but in this patch, support is added for the tags so that the HTML Processor can process documents containing them.
There was a design discussion about introducing a constant to communicate "any of the H1 - H6 elements" but this posed a number of challenges that don't need to be answered in this patch. For the time being, because the HTML specification treats H1 - H6 specially as a single kind of element, the HTML Processor uses an internal hard-coded string to indicate this. By using a hard-coded string it's possible to avoid introducing a class constant which cannot be made private due to PHP's class design. In the future, this will probably appear as a special constant in a new constant-containing class.
Props dmsnell, jonsurrell.
Fixes#60060.
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This patch adds support to process the BUTTON element. This requires adding some additional semantic rules to handle situations where a BUTTON element is already in scope.
Also included is a fixup to enforce that `WP_HTML_Processor::next_tag()` never returns for a tag closer. This is useful with the Tag Processor, but not for the HTML Processor. There were tests relying on this behavior to assert that internal processes were working as they should, but those tests have been updated to use the semi-private `step()` function, which does stop on tag closers.
This patch is one in a series of changes to expand support within the HTML API, moving gradually to allow for more focused changes that are easier to review and test. The HTML Processor is a work in progress with a certain set of features slated to be ready and tested by 6.4.0, but it will only contain partial support of the HTML5 specification even after that. Whenever it cannot positively recognize and process its input it bails, and certain function stubs and logical stubs exist to structure future expansions of support.
Props dmsnell.
Fixes#58961.
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Adjust the code style according to the rules that the linting process in Gutenberg requires.
There are only a couple code changes that should have no effect on the runtime:
- A missing check to verify that only `UTF-8` is supported has been added (brought up because it was identified as an undefined variable).
- A few `return false;` statements have been added to avoid having the linter complain that functions don't return a value despite indicating they return `bool`. The functions are stubs for coming support and currently `throw`, so the `return` statements are unreachable.
Props dmsnell, costdev, davidbaumwald, peterwilsoncc, SergeyBiryukov.
Fixes#58918.
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This patch introduces the //first// of //many// iterations on the evolution of the HTML API, the HTML Processor, which is built in order to understand HTML structure including nesting, misnesting, and complicated semantic rules.
In the first iteration, the HTML Processor is arbitrarily limited to a minimal subset of functionality so that we can review it, ship it, test it, and collect feedback before moving forward. This means that this patch is more or less an extension to the Tag Processor query language, providing the ability not only to scan for a tag of a given name, but also to find an HTML element in a specific nesting path.
The HTML Processor also aborts any time it encounters:
- a tag that isn't a `P`, `DIV`, `FIGURE`, `FIGCAPTION`, `IMG`, `STRONG`, `B`, `EM`, `I`, `A`, `BIG`, `CODE`, `FONT`, `SMALL`, `STRIKE`, `TT`, or `U` tag. this limit exists because many HTML elements require specific rules and we are trying to limit the number of rules introduced at once. this work is targeted at existing work in places like the image block.
- certain misnesting constructs that evoke complicated resolution inside the HTML spec. where possible and where simple to do reliably, certain parse errors are handled. in most cases the HTML Processor aborts.
The structure of the HTML Processor is established in this patch. Further spec-compliance comes through filling out //more of the same// kind and nature of code as is found in this patch. Certain critical HTML algorithms are partially supported, and where support requires more than is present, the HTML Processor acknowledges this and refuses to operate.
In this patch are explorations for how to verify that new HTML support is fully added (instead of allowing for partial updates that leave some code paths non-compliant). Performance is hard to measure since support is so limited at the current time, but it should generally follow the performance of the Tag Processor somewhat close as the overhead is minimized as much as practical.
Props dmsnell, zieladam, costdev.
Fixes#58517.
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dmsnell
Bernhard Reiter
Sergey Biryukov