Mihaela Mihaljevic
10d9525e3e
Whitespace-only text nodes are removed from the source tree for elements named by strip-space before transformation, with preserve-space and a more specific name test winning over *, and xml:space=preserve on a source element or ancestor overriding the stripping. The name sets fold across xsl:include/xsl:import. Refactors the stylesheet compile loop through a Parts accumulator to absorb the new top-level elements within the complexity budget.
331 lines
14 KiB
Swift
331 lines
14 KiB
Swift
private typealias Tree = PureXML.Model.TreeNode
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/// The accumulating declarations of a stylesheet as its top-level elements are
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/// compiled, plus the folding of an included or imported sub-stylesheet. File
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/// scope and private.
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private struct Parts {
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var templates: [PureXML.XSLT.Template] = []
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var globals: [PureXML.XSLT.Instruction] = []
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var keys: [PureXML.XSLT.Key] = []
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var output = PureXML.XSLT.Output()
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var stripSpace: Set<String> = []
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var preserveSpace: Set<String> = []
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var stylesheet: PureXML.XSLT.Stylesheet {
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PureXML.XSLT.Stylesheet(templates: templates, globals: globals, keys: keys, output: output, stripSpace: stripSpace, preserveSpace: preserveSpace)
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}
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/// Folds a sub-stylesheet in: an import has lower precedence, so its globals
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/// come before and its output is overridden by this stylesheet's.
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mutating func fold(_ sub: PureXML.XSLT.Stylesheet?, isImport: Bool) {
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guard let sub else { return }
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templates += sub.templates
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keys += sub.keys
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stripSpace.formUnion(sub.stripSpace)
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preserveSpace.formUnion(sub.preserveSpace)
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globals = isImport ? sub.globals + globals : globals + sub.globals
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output = isImport ? sub.output.merged(with: output) : output.merged(with: sub.output)
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}
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}
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/// Tree helpers for the XSLT parser. File-scope and private.
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private enum XSLTNode {
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static let namespace = "http://www.w3.org/1999/XSL/Transform"
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static func localName(_ node: Tree) -> String? {
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node.name?.localName
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}
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static func isXSL(_ node: Tree) -> Bool {
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node.kind == .element && (node.name?.namespaceURI == namespace || node.name?.prefix == "xsl")
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}
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static func attribute(_ node: Tree, _ name: String) -> String? {
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node.attributes.first { $0.name.localName == name }?.value
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}
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static func elementChildren(_ node: Tree) -> [Tree] {
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node.children.filter { $0.kind == .element }
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}
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static func children(_ node: Tree, named name: String) -> [Tree] {
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elementChildren(node).filter { localName($0) == name }
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}
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}
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public extension PureXML.XSLT {
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/// Errors compiling a stylesheet.
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enum XSLTError: Swift.Error, Equatable, Sendable, CustomStringConvertible {
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case notAStylesheet
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public var description: String {
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switch self {
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case .notAStylesheet: "the document is not an xsl:stylesheet"
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}
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}
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}
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}
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extension PureXML.XSLT {
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/// Parses an XSLT 1.0 stylesheet document into a ``Stylesheet``: its template
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/// rules (with computed default priorities) and global variables. The XSLT
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/// vocabulary is recognized by namespace or the `xsl` prefix; other elements
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/// are literal result elements.
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enum XSLTParser {
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static func parse(_ xsl: String, loader: (String) -> String? = { _ in nil }) throws -> Stylesheet {
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let root = try PureXML.parseTree(xsl)
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guard let top = stylesheetElement(root) else { throw XSLTError.notAStylesheet }
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return compile(top, loader: loader, precedence: 0)
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}
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private static func stylesheetElement(_ root: Tree) -> Tree? {
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guard let top = XSLTNode.elementChildren(root).first, XSLTNode.isXSL(top),
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XSLTNode.localName(top) == "stylesheet" || XSLTNode.localName(top) == "transform"
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else {
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return nil
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}
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return top
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}
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/// Compiles a stylesheet element, recursively folding in `xsl:include`
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/// (same import precedence) and `xsl:import` (one lower) resolved through
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/// `loader`.
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private static func compile(_ top: Tree, loader: (String) -> String?, precedence: Int) -> Stylesheet {
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var parts = Parts()
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for child in XSLTNode.elementChildren(top) where XSLTNode.isXSL(child) {
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absorb(child, into: &parts, loader: loader, precedence: precedence)
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}
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return parts.stylesheet
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}
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private static func absorb(_ child: Tree, into parts: inout Parts, loader: (String) -> String?, precedence: Int) {
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switch XSLTNode.localName(child) {
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case "template": parts.templates.append(template(child, precedence: precedence))
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case "variable", "param": parts.globals.append(variable(child))
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case "key": parts.keys.append(key(child))
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case "output": parts.output = parts.output.merged(with: parseOutput(child))
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case "strip-space": parts.stripSpace.formUnion(elementNames(child))
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case "preserve-space": parts.preserveSpace.formUnion(elementNames(child))
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case "include": parts.fold(load(child, loader: loader, precedence: precedence), isImport: false)
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case "import": parts.fold(load(child, loader: loader, precedence: precedence - 1), isImport: true)
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default: break
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}
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}
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/// The whitespace-separated element name tests of an `xsl:strip-space` or
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/// `xsl:preserve-space` element's `elements` attribute.
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private static func elementNames(_ node: Tree) -> Set<String> {
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Set((XSLTNode.attribute(node, "elements") ?? "").split(whereSeparator: \.isWhitespace).map(String.init))
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}
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private static func load(_ node: Tree, loader: (String) -> String?, precedence: Int) -> Stylesheet? {
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guard let href = XSLTNode.attribute(node, "href"), let text = loader(href),
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let root = try? PureXML.parseTree(text), let top = stylesheetElement(root)
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else {
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return nil
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}
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return compile(top, loader: loader, precedence: precedence)
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}
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private static func parseOutput(_ node: Tree) -> Output {
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Output(
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method: XSLTNode.attribute(node, "method"),
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indent: XSLTNode.attribute(node, "indent").map { $0 == "yes" },
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omitXMLDeclaration: XSLTNode.attribute(node, "omit-xml-declaration").map { $0 == "yes" },
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encoding: XSLTNode.attribute(node, "encoding"),
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version: XSLTNode.attribute(node, "version"),
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standalone: XSLTNode.attribute(node, "standalone").map { $0 == "yes" },
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)
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}
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private static func key(_ node: Tree) -> Key {
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Key(
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name: XSLTNode.attribute(node, "name") ?? "",
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match: XSLTNode.attribute(node, "match") ?? "",
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use: XSLTNode.attribute(node, "use") ?? ".",
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)
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}
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// MARK: Templates
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private static func template(_ node: Tree, precedence: Int) -> Template {
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let match = XSLTNode.attribute(node, "match")
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let priority = XSLTNode.attribute(node, "priority").flatMap(Double.init)
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?? match.map(defaultPriority) ?? 0
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let parameters = XSLTNode.children(node, named: "param").map(binding)
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let body = node.children
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.filter { !(XSLTNode.isXSL($0) && XSLTNode.localName($0) == "param") }
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.compactMap(instruction)
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return Template(
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match: match,
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name: XSLTNode.attribute(node, "name"),
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mode: XSLTNode.attribute(node, "mode"),
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priority: priority,
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importPrecedence: precedence,
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parameters: parameters,
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body: body,
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)
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}
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private static func binding(_ node: Tree) -> Binding {
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Binding(
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name: XSLTNode.attribute(node, "name") ?? "",
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select: XSLTNode.attribute(node, "select"),
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body: body(node),
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)
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}
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private static func withParameters(_ node: Tree) -> [Binding] {
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XSLTNode.children(node, named: "with-param").map(binding)
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}
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/// The XSLT default-priority rules for a match pattern.
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static func defaultPriority(_ pattern: String) -> Double {
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if pattern.contains("/") || pattern.contains("[") { return 0.5 }
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if ["*", "@*", "node()", "text()", "comment()"].contains(pattern) { return -0.5 }
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if pattern.hasSuffix(":*") { return -0.25 }
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return 0
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}
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// MARK: Bodies and instructions
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private static func body(_ node: Tree) -> [Instruction] {
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node.children.compactMap(instruction)
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}
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private static func instruction(_ node: Tree) -> Instruction? {
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switch node.kind {
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case .text, .cdata:
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let value = node.value
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return value.allSatisfy(\.isWhitespace) ? nil : .literalText(value)
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case .element:
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return XSLTNode.isXSL(node) ? xslInstruction(node) : literalElement(node)
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default:
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return nil
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}
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}
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private static func xslInstruction(_ node: Tree) -> Instruction? {
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simpleInstruction(node) ?? structuralInstruction(node)
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}
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private static func simpleInstruction(_ node: Tree) -> Instruction? {
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switch XSLTNode.localName(node) {
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case "value-of": .valueOf(select: XSLTNode.attribute(node, "select") ?? "")
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case "apply-templates": .applyTemplates(
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select: XSLTNode.attribute(node, "select"),
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mode: XSLTNode.attribute(node, "mode"),
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sorts: sorts(node),
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parameters: withParameters(node),
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)
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case "copy-of": .copyOf(select: XSLTNode.attribute(node, "select") ?? "")
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case "call-template": .callTemplate(
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name: XSLTNode.attribute(node, "name") ?? "",
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parameters: withParameters(node),
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)
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case "text": .literalText(node.stringValue)
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case "variable", "param": variable(node)
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case "copy": .copy(body: body(node))
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default: nil
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}
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}
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private static func structuralInstruction(_ node: Tree) -> Instruction? {
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switch XSLTNode.localName(node) {
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case "for-each":
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.forEach(select: XSLTNode.attribute(node, "select") ?? "", sorts: sorts(node), body: body(node))
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case "if":
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.ifInstruction(test: XSLTNode.attribute(node, "test") ?? "", body: body(node))
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case "choose":
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choose(node)
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case "element":
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.element(name: valueTemplate(XSLTNode.attribute(node, "name") ?? ""), body: body(node))
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case "attribute":
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.attribute(name: valueTemplate(XSLTNode.attribute(node, "name") ?? ""), body: body(node))
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case "number":
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.number(
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count: XSLTNode.attribute(node, "count"),
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from: XSLTNode.attribute(node, "from"),
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format: XSLTNode.attribute(node, "format") ?? "1",
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)
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case "comment":
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.comment(body: body(node))
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case "processing-instruction":
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.processingInstruction(name: valueTemplate(XSLTNode.attribute(node, "name") ?? ""), body: body(node))
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default:
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nil
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}
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}
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private static func variable(_ node: Tree) -> Instruction {
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.variable(name: XSLTNode.attribute(node, "name") ?? "", select: XSLTNode.attribute(node, "select"), body: body(node))
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}
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private static func choose(_ node: Tree) -> Instruction {
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let whens = XSLTNode.children(node, named: "when").map { branch in
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Branch(test: XSLTNode.attribute(branch, "test") ?? "", body: body(branch))
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}
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let otherwise = XSLTNode.children(node, named: "otherwise").first.map(body) ?? []
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return .choose(whens: whens, otherwise: otherwise)
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}
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private static func literalElement(_ node: Tree) -> Instruction {
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guard let name = node.name else { return .literalText("") }
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let attributes = node.attributes
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.filter { $0.name.prefix != "xmlns" && !($0.name.prefix == nil && $0.name.localName == "xmlns") }
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.map { LiteralAttribute(name: $0.name, value: valueTemplate($0.value)) }
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return .literalElement(name: name, attributes: attributes, body: body(node))
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}
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private static func sorts(_ node: Tree) -> [Sort] {
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XSLTNode.children(node, named: "sort").map { sort in
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Sort(
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select: XSLTNode.attribute(sort, "select") ?? ".",
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descending: XSLTNode.attribute(sort, "order") == "descending",
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numeric: XSLTNode.attribute(sort, "data-type") == "number",
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)
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}
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}
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// MARK: Attribute value templates
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static func valueTemplate(_ string: String) -> ValueTemplate {
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var parts: [ValuePart] = []
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var literal = ""
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let characters = Array(string)
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var index = 0
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while index < characters.count {
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let character = characters[index]
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if character == "{", index + 1 < characters.count, characters[index + 1] == "{" {
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literal.append("{")
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index += 2
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continue
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}
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if character == "}", index + 1 < characters.count, characters[index + 1] == "}" {
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literal.append("}")
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index += 2
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continue
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}
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if character == "{" {
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if !literal.isEmpty { parts.append(.literal(literal))
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literal = ""
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}
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index += 1
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var expression = ""
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while index < characters.count, characters[index] != "}" {
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expression.append(characters[index])
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index += 1
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}
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index += 1
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parts.append(.expression(expression))
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continue
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}
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literal.append(character)
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index += 1
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}
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if !literal.isEmpty { parts.append(.literal(literal)) }
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return parts
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}
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}
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}
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