Mihaela Mihaljevic
1ae6680d94
Add PureXML.XPath: a compiled location-path query engine reimplemented from the XPath 1.0 specification; no upstream code copied. - Compiler parses a path into steps; Evaluator walks the tree returning a Selection node-set (node or attribute) in document order. - Forward axes only (child, descendant //, self ., attribute @), since the value model has no parent pointers. Node tests: name, *, text(), node(), comment(). Predicates: [n], [@a], [@a='v'], [child], [child='v']. - Public surface: XPath.Query (init compiles, evaluate/elements/strings), the Selection enum (element / stringValue), QueryError, and the one-shot PureXML.xpath(_:over:). Upward/sibling axes and the full expression language are explicitly out of scope. - 12 XPath tests; 61 total.
27 lines
1.1 KiB
Swift
27 lines
1.1 KiB
Swift
public extension PureXML.XPath {
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/// An error compiling or evaluating an XPath query in the supported subset.
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enum QueryError: Swift.Error, Equatable, Sendable, CustomStringConvertible {
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case empty
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case unexpectedToken(String)
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case expectedNodeTest
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case unterminatedPredicate
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case unsupportedPredicate(String)
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/// An upward or sibling axis was used; only forward axes are supported.
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case unsupportedAxis(String)
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/// An attribute step appeared before the end of the path.
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case attributeStepNotLast
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public var description: String {
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switch self {
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case .empty: "the XPath expression is empty"
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case let .unexpectedToken(token): "unexpected token '\(token)'"
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case .expectedNodeTest: "expected a node test"
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case .unterminatedPredicate: "unterminated predicate"
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case let .unsupportedPredicate(detail): "unsupported predicate: \(detail)"
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case let .unsupportedAxis(axis): "unsupported axis: \(axis)"
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case .attributeStepNotLast: "an attribute step must be the last step"
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}
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}
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}
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}
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