Mihaela Mihaljevic
80fffd8127
Add PureXML.Validation.Schematron: compile a Schematron schema (matching schema/pattern/rule/assert/report by local name, so the ISO and legacy namespaces both work) and validate a document. A rule's context XPath selects the nodes it fires on; each assert/report test is evaluated relative to the node via the XPath context-node API. A failed assert is an error, a matched report a warning; within a pattern a node fires the first matching rule. Adds XPath.Query.nodes(over:) returning matched tree nodes so one tree can be queried repeatedly. Closes #52 Closes #53 Closes #25
54 lines
2.5 KiB
Swift
54 lines
2.5 KiB
Swift
public extension PureXML.Validation {
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/// Rule-based assertion validation (the libxml2 `schematron.h` model).
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///
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/// A Schematron schema groups `<rule>`s into `<pattern>`s. Each rule has a
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/// `context` XPath selecting the nodes it fires on, and `<assert>`/`<report>`
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/// children whose `test` XPath is evaluated relative to each context node. An
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/// `assert` whose test is false, and a `report` whose test is true, produce an
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/// ``Issue`` carrying the element's message.
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///
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/// Within a pattern a node is processed by the first rule whose context
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/// selects it. Dynamic message content (`<value-of>`, `<name>`) is rendered as
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/// its static text; the message substitution itself is not evaluated.
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struct Schematron {
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private let patterns: [SchematronPattern]
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/// Compiles a Schematron schema document. Throws if a context or test is
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/// not a valid XPath expression.
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public init(schema xml: String) throws {
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patterns = try SchematronParser.parse(xml)
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}
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/// Validates an XML document against the schema, returning one issue per
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/// failed assertion and per matched report, in document order.
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public func validate(_ xml: String) throws -> [Issue] {
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let root = try PureXML.parseTree(xml)
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var issues: [Issue] = []
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for pattern in patterns {
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evaluate(pattern, over: root, into: &issues)
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}
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return issues
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}
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private func evaluate(_ pattern: SchematronPattern, over root: PureXML.Model.TreeNode, into issues: inout [Issue]) {
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var claimed: Set<ObjectIdentifier> = []
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for rule in pattern.rules {
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for node in rule.context.nodes(over: root) where claimed.insert(ObjectIdentifier(node)).inserted {
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apply(rule.assertions, at: node, into: &issues)
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}
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}
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}
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private func apply(_ assertions: [SchematronAssertion], at node: PureXML.Model.TreeNode, into issues: inout [Issue]) {
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for assertion in assertions {
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let holds = (try? assertion.test.value(at: node).boolean) ?? false
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if assertion.isReport {
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if holds { issues.append(Issue(severity: .warning, message: assertion.message)) }
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} else if !holds {
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issues.append(Issue(severity: .error, message: assertion.message))
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}
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}
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}
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}
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}
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