Mihaela Mihaljevic
4345e6170e
Closes #75, on the validation framework. XSD instance-level features: - nillable elements: an xsi:nil="true" element is accepted (its content model is not checked) only when the element is declared nillable and carries no content; xsi:nil on a non-nillable element, or a nilled element with content, is a located error. - fixed value constraints: a present fixed attribute must equal its fixed value, and a fixed element's text must match. - default/fixed are parsed onto AttributeUse (per use) and collected per element name (nillable set + value constraints), threaded through XSDContext to the ComplexValidator. All findings are located ValidationErrors. Collection and helper methods move to same-file extensions to stay within type-body limits.
326 lines
15 KiB
Swift
326 lines
15 KiB
Swift
/// File-scope aliases for the XSD complex-type validator, kept out of the
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/// namespace to avoid nesting a type two levels deep.
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private typealias XSDFailure = PureXML.Validation.ValidationError
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private typealias XSDPath = [PureXML.Validation.PathKey]
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public extension PureXML.Schema {
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/// Validates an element against a ``ComplexType``: its attribute uses, its
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/// content model, and, recursively, each child element against the type
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/// declared for its name. Every violation is located by the element's coding
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/// path, and the results are ``PureXML/Validation/ValidationError`` values.
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struct ComplexValidator {
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/// The named type table that `ElementType.typeReference` resolves against.
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private let types: [String: ElementType]
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/// Local names of elements declared `nillable="true"`.
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private let nillableElements: Set<String>
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/// The `default`/`fixed` value constraint declared on each element name.
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private let elementConstraints: [String: ValueConstraint]
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public init(
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types: [String: ElementType] = [:],
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nillableElements: Set<String> = [],
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elementConstraints: [String: ValueConstraint] = [:],
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) {
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self.types = types
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self.nillableElements = nillableElements
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self.elementConstraints = elementConstraints
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}
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/// Validates `element` against `type` at `path`, one error per violation.
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public func validate(
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_ element: PureXML.Model.Element,
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against type: ComplexType,
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at path: [PureXML.Validation.PathKey] = [],
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) -> [PureXML.Validation.ValidationError] {
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var errors: [XSDFailure] = []
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validateAttributes(element, type, at: path, into: &errors)
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// An xsi:nil element keeps its attribute obligations but must have no
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// content; its content model is not otherwise checked.
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if let nilErrors = nilErrors(element, at: path) {
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return errors + nilErrors
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}
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validateContent(element, type.content, at: path, into: &errors)
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errors += elementFixedErrors(element, at: path)
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return errors
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}
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/// The errors from an `xsi:nil="true"` element: rejecting it when the
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/// element is not nillable, or when it carries content. Returns nil when
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/// the element is not nilled.
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private func nilErrors(_ element: PureXML.Model.Element, at path: XSDPath) -> [XSDFailure]? {
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guard Self.isNil(element) else { return nil }
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let name = element.name.localName
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if !nillableElements.contains(name) {
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return [XSDFailure(reason: "element '\(name)' is not nillable but has xsi:nil", at: path)]
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}
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if Self.hasContent(element) {
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return [XSDFailure(reason: "nil element '\(name)' must be empty", at: path)]
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}
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return []
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}
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/// The error from a `fixed` element value constraint: the element's text
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/// must equal the fixed value.
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private func elementFixedErrors(_ element: PureXML.Model.Element, at path: XSDPath) -> [XSDFailure] {
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guard let fixed = elementConstraints[element.name.localName]?.fixedValue else { return [] }
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let text = Self.textContent(element)
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return text == fixed ? [] : [XSDFailure(reason: "element '\(element.name.localName)' is fixed and must be '\(fixed)'", at: path)]
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}
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/// Validates `element` against any element type at `path`, resolving a
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/// `typeReference` through the type table.
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public func validate(
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_ element: PureXML.Model.Element,
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as type: ElementType,
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at path: [PureXML.Validation.PathKey] = [],
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) -> [PureXML.Validation.ValidationError] {
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var errors: [XSDFailure] = []
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validateChild(element, against: type, at: path, into: &errors)
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return errors
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}
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// MARK: Attributes
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private func validateAttributes(
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_ element: PureXML.Model.Element,
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_ type: ComplexType,
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at path: XSDPath,
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into errors: inout [XSDFailure],
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) {
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let present = element.attributes.filter { !Self.isNamespaceDeclaration($0) && !Self.isSchemaInstanceAttribute($0) }
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for use in type.attributes {
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let match = present.first { $0.name.localName == use.name.localName }
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if let match {
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if let error = use.type.validate(match.value) {
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errors.append(XSDFailure(reason: "attribute '\(use.name.localName)': \(error)", at: path))
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}
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if let fixed = use.valueConstraint?.fixedValue, match.value != fixed {
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errors.append(XSDFailure(reason: "attribute '\(use.name.localName)' is fixed and must be '\(fixed)'", at: path))
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}
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} else if use.required {
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errors.append(XSDFailure(reason: "missing required attribute '\(use.name.localName)'", at: path))
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}
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}
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guard !type.allowsOtherAttributes else { return }
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for attribute in present where !type.attributes.contains(where: { $0.name.localName == attribute.name.localName }) {
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errors.append(XSDFailure(reason: "undeclared attribute '\(attribute.name.localName)'", at: path))
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}
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}
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// MARK: Content
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private func validateContent(
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_ element: PureXML.Model.Element,
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_ content: ContentType,
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at path: XSDPath,
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into errors: inout [XSDFailure],
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) {
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let children = element.children.compactMap(\.element)
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switch content {
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case .empty:
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if !children.isEmpty { errors.append(XSDFailure(reason: "element must be empty", at: path)) }
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rejectText(element, at: path, into: &errors)
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case let .simpleContent(type):
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if !children.isEmpty { errors.append(XSDFailure(reason: "element must not have children", at: path)) }
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if let error = type.validate(Self.textContent(element)) {
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errors.append(XSDFailure(reason: "content: \(error)", at: path))
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}
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case let .elementOnly(particle):
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rejectText(element, at: path, into: &errors)
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validateParticle(particle, children: children, at: path, into: &errors)
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case let .mixed(particle):
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validateParticle(particle, children: children, at: path, into: &errors)
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}
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}
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private func rejectText(_ element: PureXML.Model.Element, at path: XSDPath, into errors: inout [XSDFailure]) {
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guard !Self.textContent(element).isEmpty else { return }
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errors.append(XSDFailure(reason: "element must not contain text", at: path))
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}
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// MARK: Particles
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private func validateParticle(
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_ particle: Particle,
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children: [PureXML.Model.Element],
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at path: XSDPath,
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into errors: inout [XSDFailure],
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) {
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let names = children.map(\.name)
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let structureValid: Bool = if case let .group(group) = particle.term, group.compositor == .all {
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Self.matchesAll(group, names: names)
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} else {
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ContentNFABuilder.build(particle).matchesWhole(names)
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}
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if !structureValid {
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errors.append(XSDFailure(reason: "content does not match the content model", at: path))
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return
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}
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validateChildren(children, childTypes: Self.elementTypes(in: particle.term), at: path, into: &errors)
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}
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private func validateChildren(
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_ children: [PureXML.Model.Element],
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childTypes: [String: ElementType],
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at path: XSDPath,
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into errors: inout [XSDFailure],
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) {
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let steps = Self.childSteps(children)
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for (child, step) in zip(children, steps) {
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guard let declared = childTypes[Self.key(child.name)] else { continue }
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validateChild(child, against: declared, at: path + [step], into: &errors)
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}
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}
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private func validateChild(
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_ child: PureXML.Model.Element,
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against declared: ElementType,
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at path: XSDPath,
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into errors: inout [XSDFailure],
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) {
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// An instance `xsi:type` overrides the declared type, provided the named
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// type exists in the schema. Resolve to the type itself rather than a
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// reference so re-entry does not re-read the same xsi:type.
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var declared = declared
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if let overriding = Self.xsiTypeName(child), let resolved = types[overriding] {
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declared = resolved
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}
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switch declared {
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case let .simple(simple):
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if let nilErrors = nilErrors(child, at: path) {
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errors += nilErrors
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return
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}
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if !child.children.compactMap(\.element).isEmpty {
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errors.append(XSDFailure(reason: "'\(child.name.localName)' must not have children", at: path))
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}
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if let error = simple.validate(Self.textContent(child)) {
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errors.append(XSDFailure(reason: "'\(child.name.localName)': \(error)", at: path))
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}
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errors += elementFixedErrors(child, at: path)
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case let .complex(complex):
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errors.append(contentsOf: validate(child, against: complex, at: path))
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case let .typeReference(name):
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guard let resolved = types[name] else {
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errors.append(XSDFailure(reason: "unknown type '\(name)'", at: path))
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return
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}
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validateChild(child, against: resolved, at: path, into: &errors)
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}
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}
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// MARK: Helpers
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/// The coding-path step for each child: its name, with a sibling index only
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/// when more than one child shares that name.
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private static func childSteps(_ children: [PureXML.Model.Element]) -> [PureXML.Validation.PathKey] {
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var totals: [String: Int] = [:]
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for child in children {
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totals[child.name.description, default: 0] += 1
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}
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var seen: [String: Int] = [:]
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return children.map { child in
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let name = child.name.description
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let index = (seen[name] ?? 0) + 1
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seen[name] = index
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return (totals[name] ?? 0) > 1 ? .element(name, index: index) : .element(name)
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}
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}
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/// Validates an `all` group order-independently: every child matches a
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/// member within its occurrence bounds, and each member meets its minimum.
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private static func matchesAll(_ group: Group, names: [PureXML.Model.QualifiedName]) -> Bool {
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var counts = [Int](repeating: 0, count: group.particles.count)
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for name in names {
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guard let index = group.particles.indices.first(where: { position in
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let member = group.particles[position]
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let room = member.maxOccurs.map { counts[position] < $0 } ?? true
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return room && label(of: member.term).matches(name)
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}) else { return false }
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counts[index] += 1
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}
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for (index, member) in group.particles.enumerated() where counts[index] < member.minOccurs {
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return false
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}
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return true
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}
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private static func label(of term: Term) -> TermLabel {
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if case let .element(name, _) = term { return .name(name) }
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return .any
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}
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private static func elementTypes(in term: Term) -> [String: ElementType] {
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var result: [String: ElementType] = [:]
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collectTypes(term, into: &result)
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return result
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}
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private static func collectTypes(_ term: Term, into result: inout [String: ElementType]) {
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switch term {
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case let .element(name, type):
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if let type { result[key(name)] = type }
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case let .group(group):
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for member in group.particles {
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collectTypes(member.term, into: &result)
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}
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case .wildcard:
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break
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}
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}
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private static func key(_ name: PureXML.Model.QualifiedName) -> String {
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"{\(name.namespaceURI ?? "")}\(name.localName)"
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}
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private static func textContent(_ element: PureXML.Model.Element) -> String {
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let text = element.children.reduce(into: "") { result, child in
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switch child {
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case let .text(value), let .cdata(value): result += value
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default: break
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}
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}
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return text.trimmingXMLWhitespace()
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}
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private static func isNamespaceDeclaration(_ attribute: PureXML.Model.Attribute) -> Bool {
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attribute.name.prefix == "xmlns" || (attribute.name.prefix == nil && attribute.name.localName == "xmlns")
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}
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/// Whether an attribute belongs to the XML Schema instance namespace
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/// (`xsi:type`, `xsi:nil`, and the schema-location hints), which are
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/// processing directives rather than declared attributes.
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private static func isSchemaInstanceAttribute(_ attribute: PureXML.Model.Attribute) -> Bool {
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attribute.name.namespaceURI == "http://www.w3.org/2001/XMLSchema-instance" || attribute.name.prefix == "xsi"
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}
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/// The local name of an element's `xsi:type` attribute value, or nil when it
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/// carries none. Recognizes the attribute by the XML Schema instance
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/// namespace or, failing namespace resolution, the conventional `xsi` prefix.
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private static func xsiTypeName(_ element: PureXML.Model.Element) -> String? {
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let schemaInstance = "http://www.w3.org/2001/XMLSchema-instance"
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let match = element.attributes.first { attribute in
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attribute.name.localName == "type"
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&& (attribute.name.namespaceURI == schemaInstance || attribute.name.prefix == "xsi")
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}
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return match.map { $0.value.split(separator: ":").last.map(String.init) ?? $0.value }
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}
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}
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}
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extension PureXML.Schema.ComplexValidator {
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/// Whether the element carries `xsi:nil="true"`.
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static func isNil(_ element: PureXML.Model.Element) -> Bool {
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element.attributes.contains { attribute in
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attribute.name.localName == "nil"
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&& (attribute.name.namespaceURI == "http://www.w3.org/2001/XMLSchema-instance" || attribute.name.prefix == "xsi")
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&& attribute.value == "true"
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}
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}
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/// Whether the element has any child element or non-whitespace text.
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static func hasContent(_ element: PureXML.Model.Element) -> Bool {
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!textContent(element).isEmpty || element.children.contains { if case .element = $0 { true } else { false } }
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}
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}
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