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bez specs inline-style-cascade.md
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enabled: true touches: [crates/dom/**, roadmap.md] depends-on: [] #

Read the inline style="" attribute into the cascade #

held-out-rerun's WPT re-measurement found that every remaining failure in that corpus traces to one gap: style="..." attribute values are never read into the cascade, only <style> block rulesets are. TElement::style_attribute() in crates/dom/src/style.rs is a hard-coded stub returning None — Stylo's own hook for this, left unimplemented since Phase 0's corpus styled everything through <style>, never style="...". ElementData::attr (crates/dom/src/node.rs) already returns the raw attribute string verbatim, proven by parse.rs's attributes_are_captured_with_name_and_value test — no parser change is needed.

Implement style_attribute() to look up self.element().attr("style") and, when present and non-empty, parse it with Stylo's own style::properties::declaration_block::parse_style_attribute — the same function Servo and Gecko use for this — then cache the resulting Arc<Locked<PropertyDeclarationBlock>> somewhere ElementData can own it; today it has nowhere to. Document::parse (crates/dom/src/style.rs) already constructs the UrlExtraData, QuirksMode and shared lock this needs; retain whichever of those the cache requires.

Stylo's rule collector already inserts the style attribute at the correct cascade level the moment style_attribute() stops returning None — same_tree_author_normal() after stylesheet author-normal rules, and same_tree_author_important() separately for !important declarations. No specificity or cascade-origin logic belongs in this codebase; do not add any — correctness comes from Stylo's own rule tree, not from anything written here.

Requirements:

  • A style="" attribute with no matching stylesheet rule applies on its own.
  • An inline declaration overrides a stylesheet rule on the same property, and a stylesheet !important declaration still overrides a plain inline one. Model both as new tests in crates/dom/src/computed.rs, following an_author_margin_on_body_overrides_the_user_agent_default.
  • crates/dom/src/bin/style_check.rs's corpus (built from crates/harness/src/cases.rs) has no style= fixture today. Add one, or say in the Result section why it wasn't needed to prove the fix — don't leave the question unanswered.

The float-exclusion gap held-out-rerun also found on auto-margins-used-values-with-floats.tentative.html (a float: right box declared in a <style> block never excluded from the block formatting context) is a separate, independent defect. Do not fix it here.

cargo test --workspace must pass. style_check and box_check must report the same 2958/2958 corpus figure they do today, unless a new style= fixture was deliberately added to the corpus for this work — if any other count moves, a recipe was relying on the gap; report it in the Result section rather than adjusting the recipe. Do not run held_out_check here; a future re-measurement spec does that once this has landed, so the before-and-after is measured on a committed base.