Disallow contraction of {scroll,view}-timeline shorthands when longhands have dissimilar cardinality #56181
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…nds have dissimilar cardinality According to https://drafts.csswg.org/cssom/#serializing-css-values (step 1.2) shorthands should only be contracted if they can exactly represent the values of all it's longhands - that was not the case for these tests. Take for example the test which expected ```css scroll-timeline-name: --a, --b, --c; scroll-timeline-axis: inline, inline; ``` to be serialized as ```css scroll-timeline: --a inline, --b inline, --c inline; ``` The serialized value actually represents the longhand value for `scroll-timeline-axis` of `inline, inline, line` (3 elements instead of the original 2). This matches the behavior of Chrome & Firefox.
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The remaining failing tests in scroll-timeline-shorthand.html are due to either: a) incorrect tests, see web-platform-tests/wpt#56181 or; b) a wider issue where we collapse coordinating value list longhand properties to a single value when we shouldn't.
Calme1709
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The remaining failing tests in view-timeline-shorthand.html are due to either: a) incorrect tests, see web-platform-tests/wpt#56181 or; b) a wider issue where we collapse coordinating value list longhand properties to a single value when we shouldn't.
Calme1709
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The remaining failing tests in scroll-timeline-shorthand.html are due to either: a) incorrect tests, see web-platform-tests/wpt#56181 or; b) a wider issue where we collapse coordinating value list longhand properties to a single value when we shouldn't.
Calme1709
added a commit
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that referenced
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Nov 23, 2025
The remaining failing tests in view-timeline-shorthand.html are due to either: a) incorrect tests, see web-platform-tests/wpt#56181 or; b) a wider issue where we collapse coordinating value list longhand properties to a single value when we shouldn't.
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According to https://drafts.csswg.org/cssom/#serializing-css-values (step 1.2) shorthands should only be contracted if they can exactly represent the values of all it's longhands - that was not the case for these tests. Take for example the test which expected
to be serialized as
The serialized value actually represents the longhand value for
scroll-timeline-axisofinline, inline, line(3 elements instead of the original 2).This matches the behavior of Chrome & Firefox.