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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2021-2022 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
//
//===----------------------------------------------------------------------===//
@_implementationOnly import _RegexParser
@available(SwiftStdlib 5.7, *)
extension Regex {
/// The literal pattern for this regex.
///
/// This is non-`nil` when used on a regex that can be represented as a
/// string. The literal pattern may be different from the literal or string
/// that was used to create the regex, though parsing the `_literalPattern`
/// always generates the same internal representation as the original regex.
///
/// // The literal pattern for some regexes is identical to the original:
/// let regex1 = /(\d+):(\d+)/
/// // regex1._literalPattern == #"(\d+):(\d+)"#
///
/// // The literal pattern for others is different, but equivalent:
/// let regex2 = /\p{isName=BEE}/
/// // regex2._literalPattern == #"\N{BEE}"#
///
/// If this regex includes components that cannot be represented in a regex
/// literal, such as a capture transform or a custom parser that conforms to
/// the `CustomConsumingRegexComponent` protocol, this property is `nil`.
///
/// The value of this property may change between different releases of Swift.
@available(SwiftStdlib 6.0, *)
public var _literalPattern: String? {
var gen = LiteralPrinter(options: MatchingOptions())
gen.outputNode(self.program.tree.root)
return gen.canonicalLiteralString
}
}
enum PatternSegment {
case converted(String)
case inconvertible(DSLTree.Node)
var string: String? {
switch self {
case let .converted(str):
return str
case .inconvertible:
return nil
}
}
}
fileprivate struct LiteralPrinter {
var options: MatchingOptions
private var segments: [PatternSegment] = []
init(options: MatchingOptions) {
self.options = options
}
var canonicalLiteralString: String? {
var result = ""
result.reserveCapacity(segments.count)
for segment in segments {
guard let str = segment.string else {
return nil
}
result.append(str)
}
return result
}
mutating func output(_ str: String) {
segments.append(.converted(str))
}
mutating func saveInconvertible(_ node: DSLTree.Node) {
segments.append(.inconvertible(node))
}
}
extension LiteralPrinter {
mutating func outputNode(_ node: DSLTree.Node) {
switch node {
case let .orderedChoice(children):
outputAlternation(children)
case let .concatenation(children):
outputConcatenation(children)
case let .capture(name, nil, child, nil):
options.beginScope()
defer { options.endScope() }
outputCapture(name, child)
case .capture:
// Captures that use a reference or a transform are unsupported
saveInconvertible(node)
case let .nonCapturingGroup(kind, child):
guard let kindPattern = kind._patternString else {
saveInconvertible(node)
return
}
options.beginScope()
defer { options.endScope() }
output(kindPattern)
if case .changeMatchingOptions(let optionSequence) = kind.ast {
options.apply(optionSequence)
}
outputNode(child)
output(")")
case let .ignoreCapturesInTypedOutput(child):
outputNode(child)
case .convertedRegexLiteral(let node, _):
outputNode(node)
case let .quantification(amount, kind, node):
outputQuantification(amount, kind, node)
case let .customCharacterClass(charClass):
outputCustomCharacterClass(charClass)
case let .atom(atom):
outputAtom(atom)
case let .quotedLiteral(literal):
output(prepareQuotedLiteral(literal))
case .trivia(_):
// TODO: Include trivia?
return
case .empty:
return
case .conditional, .absentFunction, .consumer, .matcher, .characterPredicate:
saveInconvertible(node)
}
}
mutating func outputAlternation(_ children: [DSLTree.Node]) {
guard let first = children.first else { return }
outputNode(first)
for child in children.dropFirst() {
output("|")
outputNode(child)
}
}
mutating func outputConcatenation(_ children: [DSLTree.Node]) {
for child in children {
outputNode(child)
}
}
mutating func outputCapture(_ name: String?, _ child: DSLTree.Node) {
if let name {
output("(?<\(name)>")
} else {
output("(")
}
outputNode(child)
output(")")
}
func requiresGrouping(_ node: DSLTree.Node) -> Bool {
switch node {
case .concatenation(let children):
switch children.count {
case 0:
return false
case 1:
return requiresGrouping(children.first!)
default:
return true
}
case .quotedLiteral(let literal):
return prepareQuotedLiteral(literal).count > 1
default:
return false
}
}
mutating func outputQuantification(
_ amount: DSLTree._AST.QuantificationAmount,
_ kind: DSLTree.QuantificationKind,
_ child: DSLTree.Node
) {
// RegexBuilder regexes can have children that need
if requiresGrouping(child) {
output("(?:")
outputNode(child)
output(")")
} else {
outputNode(child)
}
switch amount.ast {
case .zeroOrMore:
output("*")
case .oneOrMore:
output("+")
case .zeroOrOne:
output("?")
case let .exactly(n):
output("{\(n.value!)}")
case let .nOrMore(n):
output("{\(n.value!),}")
case let .upToN(n):
output("{,\(n.value!)}")
case let .range(low, high):
output("{\(low.value!),\(high.value!)}")
#if RESILIENT_LIBRARIES
@unknown default:
fatalError()
#endif
}
outputQuantificationKind(kind)
}
mutating func outputQuantificationKind(_ kind: DSLTree.QuantificationKind) {
switch kind {
case .`default`:
// We can treat this as if the current default had been given explicity.
outputQuantificationKind(
.explicit(.init(ast: options.defaultQuantificationKind)))
case let .explicit(kind):
switch kind.ast {
case .eager:
output(options.isReluctantByDefault ? "?" : "")
case .reluctant:
output(options.isReluctantByDefault ? "" : "?")
case .possessive:
output("+")
#if RESILIENT_LIBRARIES
@unknown default:
fatalError()
#endif
}
case let .syntax(kind):
// Syntactically-specified quantification modifiers can stay as-is.
switch kind.ast {
case .eager:
output("")
case .reluctant:
output("?")
case .possessive:
output("+")
#if RESILIENT_LIBRARIES
@unknown default:
fatalError()
#endif
}
}
}
mutating func outputAssertion(_ assertion: DSLTree.Atom.Assertion) {
switch assertion {
case .startOfSubject:
output(#"\A"#)
case .endOfSubjectBeforeNewline:
output(#"\Z"#)
case .endOfSubject:
output(#"\z"#)
case .resetStartOfMatch:
output(#"\K"#)
case .firstMatchingPositionInSubject:
output(#"\G"#)
case .textSegment:
output(#"\y"#)
case .notTextSegment:
output(#"\Y"#)
case .startOfLine:
if options.anchorsMatchNewlines {
output(#"^"#)
} else {
output(#"(?m:^)"#)
}
case .endOfLine:
if options.anchorsMatchNewlines {
output(#"$"#)
} else {
output(#"(?m:$)"#)
}
case .caretAnchor:
output("^")
case .dollarAnchor:
output("$")
case .wordBoundary:
output(#"\b"#)
case .notWordBoundary:
output(#"\B"#)
}
}
mutating func outputAtom(_ atom: DSLTree.Atom) {
switch atom {
case .char(let char):
output(char.escapingForLiteral)
case .scalar(let scalar):
output(scalar.escapedString)
case .any:
if options.dotMatchesNewline {
output(".")
} else {
output("(?s:.)")
}
case .anyNonNewline:
if options.dotMatchesNewline {
output("(?-s:.)")
} else {
output(".")
}
case .dot:
output(".")
case .characterClass(let charClass):
if let patt = charClass._patternString {
output(patt)
} else {
saveInconvertible(.atom(atom))
}
case .assertion(let assertion):
outputAssertion(assertion)
case .backreference(let backref):
outputReference(backref)
case .symbolicReference(_):
// RegexBuilder only
saveInconvertible(.atom(atom))
case .changeMatchingOptions(let optionSequence):
output(optionSequence.ast._patternString)
output(")")
options.apply(optionSequence.ast)
case .unconverted(let atom):
outputUnconvertedAST(atom.ast)
}
}
mutating func outputReference(_ ref: DSLTree._AST.Reference) {
switch ref.ast.kind {
case .absolute(let number):
guard let value = number.value else {
saveInconvertible(.atom(.backreference(ref)))
return
}
if value < 10 {
output("\\\(value)")
} else {
output("\\g{\(value)}")
}
case .relative(let number):
guard let value = number.value else {
saveInconvertible(.atom(.backreference(ref)))
return
}
let prefix = value < 0 ? "-" : "+"
output("\\g{\(prefix)\(abs(value))}")
case .named(let name):
output("\\g{\(name)}")
#if RESILIENT_LIBRARIES
@unknown default:
fatalError()
#endif
}
}
func prepareQuotedLiteral(_ literal: String) -> String {
if options.usesExtendedWhitespace || literal.containsRegexMetaCharacters {
return #"\Q\#(literal)\E"#
} else {
return literal.escapingConfusableCharacters()
}
}
mutating func outputCustomCharacterClass(_ charClass: DSLTree.CustomCharacterClass) {
// Sometimes we end up with a singly-wrapped CCC — flatten it out
if !charClass.isInverted {
let trivialessMembers = charClass.members.filter {
if case .trivia = $0 { return false } else { return true }
}
if trivialessMembers.count == 1,
case let .custom(inner) = trivialessMembers[0] {
outputCustomCharacterClass(inner)
return
}
}
output(charClass.isInverted ? "[^" : "[")
for member in charClass.members {
switch member {
case let .atom(atom):
outputAtom(atom)
case let .range(low, high):
outputAtom(low)
output("-")
outputAtom(high)
case let .custom(charClass):
outputCustomCharacterClass(charClass)
case let .quotedLiteral(literal):
if options.usesExtendedWhitespace || literal.containsRegexMetaCharacters {
output(#"\Q\#(literal)\E"#)
} else {
output(literal)
}
case .trivia(_):
// TODO: ignore trivia?
break
case let .intersection(left, right):
outputCustomCharacterClass(left)
output("&&")
outputCustomCharacterClass(right)
case let .subtraction(left, right):
outputCustomCharacterClass(left)
output("--")
outputCustomCharacterClass(right)
case let .symmetricDifference(left, right):
outputCustomCharacterClass(left)
output("~~")
outputCustomCharacterClass(right)
}
}
output("]")
}
mutating func outputUnconvertedAST(_ ast: AST.Atom) {
switch ast.kind {
case let .property(property):
if let base = property._regexBase {
output(base)
} else {
saveInconvertible(.atom(.unconverted(.init(ast: ast))))
}
case let .namedCharacter(name):
output("\\N{\(name)}")
default:
saveInconvertible(.atom(.unconverted(.init(ast: ast))))
}
}
}
// MARK: - Supporting extensions
fileprivate let metachars = Set(#"\[](){}|+*?^$.-"#)
extension String {
var containsRegexMetaCharacters: Bool {
contains(where: \.isRegexMetaCharacter)
}
func escapingConfusableCharacters() -> String {
lazy.map(\.escapingConfusable).joined()
}
}
extension UnicodeScalar {
var escapedString: String {
switch self {
case "\n": return #"\n"#
case "\r": return #"\r"#
case "\t": return #"\t"#
default:
let code = String(value, radix: 16, uppercase: true)
let prefix = code.count <= 4
? #"\u"# + String(repeating: "0", count: 4 - code.count)
: #"\U"# + String(repeating: "0", count: 8 - code.count)
return prefix + code
}
}
}
extension Character {
var isRegexMetaCharacter: Bool {
metachars.contains(self)
}
var escapingConfusable: String {
if isConfusable {
return String(unicodeScalars.first!) +
unicodeScalars.dropFirst().lazy.map(\.escapedString).joined()
} else {
return String(self)
}
}
var escapingForLiteral: String {
if isRegexMetaCharacter {
return "\\\(self)"
} else {
return escapingConfusable
}
}
}
// MARK: Pattern Strings
// Pattern representation for the types below is unaffected by the regex's
// options state, so they can be pure conversions.
extension DSLTree.Atom.CharacterClass {
fileprivate var _patternString: String? {
switch self {
case .digit:
return #"\d"#
case .notDigit:
return #"\D"#
case .horizontalWhitespace:
return #"\h"#
case .notHorizontalWhitespace:
return #"\H"#
case .newlineSequence:
return #"\R"#
case .notNewline:
return #"\N"#
case .whitespace:
return #"\s"#
case .notWhitespace:
return #"\S"#
case .verticalWhitespace:
return #"\v"#
case .notVerticalWhitespace:
return #"\V"#
case .word:
return #"\w"#
case .notWord:
return #"\W"#
case .anyGrapheme:
return #"\X"#
case .anyUnicodeScalar:
return nil
}
}
}
extension AST.MatchingOption.Kind {
fileprivate var _patternString: String? {
switch self {
// PCRE options
case .caseInsensitive: return "i"
case .allowDuplicateGroupNames: return "J"
case .multiline: return "m"
case .namedCapturesOnly: return "n"
case .singleLine: return "s"
case .reluctantByDefault: return "U"
case .extended: return "x"
case .extraExtended: return "xx"
// ICU options
case .unicodeWordBoundaries: return "w"
// Oniguruma options
case .asciiOnlyDigit: return "D"
case .asciiOnlyPOSIXProps: return "P"
case .asciiOnlySpace: return "S"
case .asciiOnlyWord: return "W"
// Oniguruma text segment options (these are mutually exclusive and cannot
// be unset, only flipped between)
case .textSegmentGraphemeMode: return "y{g}"
case .textSegmentWordMode: return "y{w}"
// Swift semantic matching level
case .graphemeClusterSemantics: return "X"
case .unicodeScalarSemantics: return "u"
case .byteSemantics: return "b"
// Swift-only default possessive quantifier
case .possessiveByDefault: return nil
// NSRE Compatibility option; no literal representation
case .nsreCompatibleDot: return nil
#if RESILIENT_LIBRARIES
@unknown default:
fatalError()
#endif
}
}
}
extension AST.MatchingOptionSequence {
fileprivate var _patternString: String {
let adding = adding.compactMap(\.kind._patternString).joined()
let removing = removing.compactMap(\.kind._patternString).joined()
if resetsCurrentOptions {
assert(removing.isEmpty)
return "(?^\(adding)"
} else {
return "(?\(adding)"
+ (removing.isEmpty ? "" : "-\(removing)")
}
}
}
extension DSLTree._AST.GroupKind {
fileprivate var _patternString: String? {
switch self.ast {
case .capture: return "("
case .namedCapture(let n): return "(?<\(n.value)>"
case .balancedCapture(_): return nil
case .nonCapture: return "(?:"
case .nonCaptureReset: return "(?|"
case .atomicNonCapturing: return "(?>"
case .lookahead: return "(?="
case .negativeLookahead: return "(?!"
case .nonAtomicLookahead: return "(?*"
case .lookbehind: return "(?<="
case .negativeLookbehind: return "(?<!"
case .nonAtomicLookbehind: return "(?<*"
case .scriptRun: return "(*sr:"
case .atomicScriptRun: return "(*asr:"
case let .changeMatchingOptions(sequence):
return sequence._patternString + ":"
#if RESILIENT_LIBRARIES
@unknown default:
fatalError()
#endif
}
}
}
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