PureXML/Sources/Schema/XSDContext.swift
Mihaela Mihaljevic 9a1bb652a7 fix(schema): content-free restriction of emptiable base, substitution-group declaration order
Two more Particle Valid (Restriction) over-rejections.

A derived particle that can never contribute a child (its own maxOccurs="0", or
a group whose every member is content-free) accepts only the empty sequence, so
it validly restricts any emptiable base. Checked before the structural cases,
which previously recursed into the members of a maxOccurs="0" group and rejected
it for their own occurrences (particlesW006).

Substitution-group expansion now lists members in declaration order: the closure
walk used a popLast() stack that reversed them, so a reference to a head expanded
to choice(head, m2, m1) and an order-preserving RecurseLax restriction by
choice(m1, m2) could not map (elemZ027a). The choice/choice restriction stays
order-preserving, as the W3C suite requires (choice(b|a) is not a valid
restriction of choice(a|b), particlesT002); only the expansion order is fixed.
The expansion is shared with instance validation and the determinism check, both
order-neutral.

XSTS: valid schemas rejected 4 to 2, no other bucket raised. The pinned XSTS
baselines (never asserted under a plain swift test, the suite being opt-in) are
corrected to the measured 2/520/180/160.
2026-06-14 22:48:12 +02:00

246 lines
12 KiB
Swift

/// A schema-document tree node.
typealias XSDTree = PureXML.Model.TreeNode
extension PureXML.Schema {
/// Tree-access helpers and document collection shared by the schema parser
/// across its files.
enum XSDNode {
static func localName(_ node: XSDTree) -> String? {
node.name?.localName
}
static func attribute(_ node: XSDTree, _ name: String) -> String? {
node.attributes.first { $0.name.localName == name }?.value
}
static func elementChildren(_ node: XSDTree) -> [XSDTree] {
node.children.filter { $0.kind == .element }
}
static func children(_ node: XSDTree, named name: String) -> [XSDTree] {
elementChildren(node).filter { localName($0) == name }
}
static func firstChild(_ node: XSDTree, named name: String) -> XSDTree? {
children(node, named: name).first
}
static func stripPrefix(_ qualified: String) -> String {
qualified.split(separator: ":").last.map(String.init) ?? qualified
}
/// The prefix part of a QName (`p` in `p:local`), or nil when unprefixed.
static func prefix(_ qualified: String) -> String? {
let parts = qualified.split(separator: ":", maxSplits: 1)
return parts.count == 2 ? String(parts[0]) : nil
}
/// The namespace prefix bindings declared on a schema-root element:
/// `xmlns:p="..."` keyed by `p`, the default `xmlns="..."` under the empty key.
static func namespaceBindings(of schema: XSDTree) -> [String: String] {
var bindings: [String: String] = [:]
for attribute in schema.attributes {
if attribute.name.prefix == "xmlns" {
bindings[attribute.name.localName] = attribute.value
} else if attribute.name.prefix == nil, attribute.name.localName == "xmlns" {
bindings[""] = attribute.value
}
}
return bindings
}
/// The namespace URI a reference QName resolves to, given the schema's prefix
/// bindings: a prefixed name uses its prefix's binding, an unprefixed name the
/// default-namespace binding (nil when none is declared).
static func referenceNamespace(_ qualified: String, _ bindings: [String: String]) -> String? {
if let prefix = prefix(qualified) {
return bindings[prefix]
}
return bindings[""]
}
static func occurrence(_ node: XSDTree) -> (min: Int, max: Int?) {
let minimum = attribute(node, "minOccurs").flatMap(Int.init) ?? 1
let maximumText = attribute(node, "maxOccurs")
let maximum: Int? = maximumText == "unbounded" ? nil : (maximumText.flatMap(Int.init) ?? 1)
return (minimum, maximum)
}
/// Collects the schema's own element and a transitive closure of the
/// schemas it pulls in through `include`, `import`, and `redefine`
/// (resolved through `loader` by `schemaLocation`), base schemas first so
/// the including schema's definitions take precedence. A `redefine`
/// element is itself returned as a container so its nested redefinitions
/// override the schema it includes.
static func collectContainers(
_ schema: XSDTree,
_ loader: (String) -> String?,
_ visited: inout Set<String>,
) -> [XSDTree] {
var containers: [XSDTree] = []
for child in elementChildren(schema) {
let kind = localName(child)
guard kind == "include" || kind == "import" || kind == "redefine",
let location = attribute(child, "schemaLocation"), !visited.contains(location)
else {
continue
}
visited.insert(location)
let sub = loader(location).flatMap { try? PureXML.parseTree($0) }
.flatMap { root in elementChildren(root).first { localName($0) == "schema" } }
if let sub { containers += collectContainers(sub, loader, &visited) }
if kind == "redefine" { containers.append(child) }
}
containers.append(schema)
return containers
}
/// The transitive substitution-group membership across all definition
/// containers: each head element maps to every element that may substitute
/// for it, directly or through a chain of heads.
static func substitutionMembers(_ containers: [XSDTree]) -> [String: [String]] {
var direct: [String: [String]] = [:]
for container in containers {
for element in children(container, named: "element") {
guard let name = attribute(element, "name"), let head = attribute(element, "substitutionGroup") else {
continue
}
direct[stripPrefix(head), default: []].append(name)
}
}
var closure: [String: [String]] = [:]
for head in direct.keys {
// Breadth-first in document order: a `popLast()` stack would reverse the
// members, but the substitution-group expansion must stay in declaration
// order. The order-preserving RecurseLax restriction check relies on it
// (a base `choice(head, m1, m2)` must list `m1` before `m2` so a derived
// `choice(m1, m2)` maps in order).
var members: [String] = []
var queue = direct[head] ?? []
var seen: Set<String> = []
var index = 0
while index < queue.count {
let member = queue[index]
index += 1
guard seen.insert(member).inserted else { continue }
members.append(member)
queue += direct[member] ?? []
}
closure[head] = members
}
return closure
}
}
/// The result of compiling a schema document: its global element
/// declarations, its named-type table, and the identity constraints declared
/// on each element name.
struct XSDCompiled {
var elements: [String: ElementType]
var types: [String: ElementType]
var constraints: [String: [IdentityConstraint]]
/// Local names of elements declared `nillable="true"`.
var nillableElements: Set<String> = []
/// The `default`/`fixed` value constraint declared on each element name.
var elementConstraints: [String: ValueConstraint] = [:]
/// Local names of complex types declared `abstract="true"`: an element of
/// such a type must supply an `xsi:type` naming a concrete derived type.
var abstractTypes: Set<String> = []
/// Local names of element declarations declared `abstract="true"`: they may
/// not appear in an instance directly, only through a substitution member.
var abstractElements: Set<String> = []
/// Derivation methods the named type forbids when used through `xsi:type`.
var typeBlock: [String: Set<DerivationMethod>] = [:]
/// Derivation methods each element declaration forbids through `xsi:type`.
var elementBlock: [String: Set<DerivationMethod>] = [:]
/// Each named complex type's base type and derivation method, the backbone
/// the `block` check walks from an `xsi:type` to its declared type.
var typeDerivation: [String: TypeDerivation] = [:]
/// Derivation methods each named type declares `final`, for the
/// schema-consistency rules.
var typeFinal: [String: Set<DerivationMethod>] = [:]
/// The schema's target namespace, so the root element's namespace can be
/// checked against it.
var targetNamespace: String?
/// Schema-validity findings gathered while parsing (malformed facet
/// definitions and the like), reported together with the model-level
/// consistency findings when the schema is compiled.
var schemaErrors: [String] = []
}
/// Collects schema-validity findings during parsing. A reference type so the
/// findings survive the value-type ``XSDContext``'s copies (`visiting(_:)`):
/// every copy shares the one collector, and the parser harvests it at the end.
final class SchemaDiagnostics {
private(set) var errors: [String] = []
func report(_ message: String) {
errors.append(message)
}
/// The findings with exact-duplicate messages removed, first occurrence
/// kept. The same malformed definition is visited more than once (named
/// simple types resolve over repeated passes), so dedup keeps one finding
/// per distinct problem.
var deduplicated: [String] {
var seen: Set<String> = []
return errors.filter { seen.insert($0).inserted }
}
}
/// The parsing context: the named simple types resolved so far, plus the
/// definition nodes for named attribute groups and model groups (so their
/// refs can be expanded), and a guard against cyclic group references.
struct XSDContext {
var simpleTypes: [String: SimpleType]
var attributeGroups: [String: XSDTree]
/// Top-level (global) attribute declaration nodes by name, so an
/// `<attribute ref="...">` resolves to the global declaration's type.
var globalAttributes: [String: XSDTree] = [:]
var groups: [String: XSDTree]
/// Named complex-type definition nodes, so a `complexContent` derivation can
/// resolve and compose its base type's content model and attributes.
var complexTypeNodes: [String: XSDTree] = [:]
/// The schema's target namespace, for resolving `##other`/`##targetNamespace`
/// in wildcard constraints and qualifying global and qualified-form local
/// declarations.
var targetNamespace: String?
/// Namespace prefix bindings declared on the schema root (`xmlns:p="..."`,
/// the default namespace under the empty key), so an `xs:element ref="p:foo"`
/// resolves to the namespace `p` is bound to rather than assuming the target
/// namespace. An imported element reference is in the imported namespace.
var namespaceBindings: [String: String] = [:]
/// Whether `elementFormDefault="qualified"`: local element declarations are
/// in the target namespace unless their own `form` overrides it.
var elementFormQualified: Bool = false
/// Whether `attributeFormDefault="qualified"`: local attribute declarations
/// are in the target namespace unless their own `form` overrides it.
var attributeFormQualified: Bool = false
/// Each substitution-group head maps to its transitive member element
/// names, so an `xs:element ref` to a head also admits its members.
var substitutions: [String: [String]] = [:]
/// Local names of element declarations declared `abstract="true"`, so a
/// reference to an abstract head expands to its members but not the head.
var abstractElements: Set<String> = []
var visitingGroups: Set<String> = []
/// Named complex types being resolved up the current `complexContent`
/// derivation chain, a guard against a cyclic base reference.
var visitingTypes: Set<String> = []
/// The shared schema-validity finding collector. A reference type, so the
/// value-type context's copies all report into the one place.
let diagnostics = SchemaDiagnostics()
func visiting(_ group: String) -> XSDContext {
var copy = self
copy.visitingGroups.insert(group)
return copy
}
func visitingType(_ type: String) -> XSDContext {
var copy = self
copy.visitingTypes.insert(type)
return copy
}
}
}