The attribute axis built an XPath node for every attribute of the element
and then filtered by the step's node test. A predicate like [@name='value']
runs that per matched element, so for a wide document it wrapped many
attributes only to discard all but one, and each wrap retains the owner
element and copies the attribute's qualified name and value.
Apply the same fusion the descendant axes use: test the raw attribute during
the walk and wrap only the ones that pass. matches delegates, for an
attribute node, to a new matchesAttribute (the attribute axis always carries
the attribute principal kind, so the reduction is exact), and the attribute
walk applies it as a keep filter. The node-set, declaration order, and
uniqueness are identical to build-then-filter.
Measured xpath ~20% faster on the 20k-item generated corpus via a same-state
A/B (count unchanged at 10000); xpath is now ~2x libxml2, down from ~13x at
the start of this work. XPathFusedAttributeTests covers every node-test kind
through the fused path, and an adversarial equivalence review found no query
whose result changes. Full suite, Apache Xalan XSLT gold output, and the WASM
build stay green.
Mihaela Mihaljevic
720263ee58