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Jan 23, 2025
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Do not cache NSLocale.current if we fail to fetch preferences #1134

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106 changes: 58 additions & 48 deletions Sources/FoundationEssentials/Locale/Locale_Cache.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -34,30 +34,30 @@ dynamic package func _localeICUClass() -> _LocaleProtocol.Type {
/// Singleton which listens for notifications about preference changes for Locale and holds cached singletons.
struct LocaleCache : Sendable, ~Copyable {
// MARK: - State

struct State {

init() {
#if FOUNDATION_FRAMEWORK
// For Foundation.framework, we listen for system notifications about the system Locale changing from the Darwin notification center.
_CFNotificationCenterInitializeDependentNotificationIfNecessary(CFNotificationName.cfLocaleCurrentLocaleDidChange!.rawValue)
#endif
}

private var cachedFixedLocales: [String : any _LocaleProtocol] = [:]
private var cachedFixedComponentsLocales: [Locale.Components : any _LocaleProtocol] = [:]

#if FOUNDATION_FRAMEWORK
private var cachedFixedIdentifierToNSLocales: [String : _NSSwiftLocale] = [:]

struct IdentifierAndPrefs : Hashable {
let identifier: String
let prefs: LocalePreferences?
}

private var cachedFixedLocaleToNSLocales: [IdentifierAndPrefs : _NSSwiftLocale] = [:]
#endif

mutating func fixed(_ id: String) -> any _LocaleProtocol {
// Note: Even if the currentLocale's identifier is the same, currentLocale may have preference overrides which are not reflected in the identifier itself.
if let locale = cachedFixedLocales[id] {
Expand All @@ -81,7 +81,7 @@ struct LocaleCache : Sendable, ~Copyable {
return locale
}
}

#if canImport(_FoundationICU)
mutating func fixedNSLocale(_ locale: _LocaleICU) -> _NSSwiftLocale {
let id = IdentifierAndPrefs(identifier: locale.identifier, prefs: locale.prefs)
Expand All @@ -102,33 +102,33 @@ struct LocaleCache : Sendable, ~Copyable {
func fixedComponents(_ comps: Locale.Components) -> (any _LocaleProtocol)? {
cachedFixedComponentsLocales[comps]
}

mutating func fixedComponentsWithCache(_ comps: Locale.Components) -> any _LocaleProtocol {
if let l = fixedComponents(comps) {
return l
} else {
let new = _localeICUClass().init(components: comps)

cachedFixedComponentsLocales[comps] = new
return new
}
}
}

let lock: LockedState<State>

static let cache = LocaleCache()
private let _currentCache = LockedState<(any _LocaleProtocol)?>(initialState: nil)

#if FOUNDATION_FRAMEWORK
private var _currentNSCache = LockedState<_NSSwiftLocale?>(initialState: nil)
#endif

fileprivate init() {
lock = LockedState(initialState: State())
}


/// For testing of `autoupdatingCurrent` only. If you want to test `current`, create a custom `Locale` with the appropriate settings using `localeAsIfCurrent(name:overrides:disableBundleMatching:)` and use that instead.
/// This mutates global state of the current locale, so it is not safe to use in concurrent testing.
func resetCurrent(to preferences: LocalePreferences) {
Expand All @@ -150,32 +150,36 @@ struct LocaleCache : Sendable, ~Copyable {
}

var current: any _LocaleProtocol {
return _currentAndCache.locale
}

fileprivate var _currentAndCache: (locale: any _LocaleProtocol, doCache: Bool) {
if let result = _currentCache.withLock({ $0 }) {
return result
return (result, true)
}

// We need to fetch prefs and try again
let (preferences, doCache) = preferences()
let locale = _localeICUClass().init(name: nil, prefs: preferences, disableBundleMatching: false)

// It's possible this was an 'incomplete locale', in which case we will want to calculate it again later.
if doCache {
return _currentCache.withLock {
if let current = $0 {
// Someone beat us to setting it - use existing one
return current
return (current, true)
} else {
$0 = locale
return locale
return (locale, true)
}
}
} else {
return (locale, false)
}

return locale
}

// MARK: Singletons

// This value is immutable, so we can share one instance for the whole process.
static let unlocalized = _LocaleUnlocalized(identifier: "en_001")

Expand All @@ -185,19 +189,19 @@ struct LocaleCache : Sendable, ~Copyable {
static let system : any _LocaleProtocol = {
_localeICUClass().init(identifier: "", prefs: nil)
}()

#if FOUNDATION_FRAMEWORK
static let autoupdatingCurrentNSLocale : _NSSwiftLocale = {
_NSSwiftLocale(Locale(inner: autoupdatingCurrent))
}()

static let systemNSLocale : _NSSwiftLocale = {
_NSSwiftLocale(Locale(inner: system))
}()
#endif

// MARK: -

func fixed(_ id: String) -> any _LocaleProtocol {
lock.withLock {
$0.fixed(id)
Expand All @@ -219,19 +223,25 @@ struct LocaleCache : Sendable, ~Copyable {
if let result = _currentNSCache.withLock({ $0 }) {
return result
}

// Create the current _NSSwiftLocale, based on the current Swift Locale.
// n.b. do not call just `current` here; instead, use `_currentAndCache`
// so that the caching status is honored
let (current, doCache) = _currentAndCache
let nsLocale = _NSSwiftLocale(Locale(inner: current))

// TODO: The current locale has an idea of not caching, which we have never honored here in the NSLocale cache
return _currentNSCache.withLock {
if let current = $0 {
// Someone beat us to setting it, use that one
return current
} else {
$0 = nsLocale
return nsLocale

if doCache {
return _currentNSCache.withLock {
if let current = $0 {
// Someone beat us to setting it, use that one
return current
} else {
$0 = nsLocale
return nsLocale
}
}
} else {
return nsLocale
}
}

Expand All @@ -240,7 +250,7 @@ struct LocaleCache : Sendable, ~Copyable {
func fixedComponents(_ comps: Locale.Components) -> any _LocaleProtocol {
lock.withLock { $0.fixedComponentsWithCache(comps) }
}

#if FOUNDATION_FRAMEWORK && !NO_CFPREFERENCES
func preferences() -> (LocalePreferences, Bool) {
// On Darwin, we check the current user preferences for Locale values
Expand All @@ -249,28 +259,28 @@ struct LocaleCache : Sendable, ~Copyable {

var prefs = LocalePreferences()
prefs.apply(cfPrefs)

if wouldDeadlock.boolValue {
// Don't cache a locale built with incomplete prefs
return (prefs, false)
} else {
return (prefs, true)
}
}

func preferredLanguages(forCurrentUser: Bool) -> [String] {
var languages: [String] = []
if forCurrentUser {
languages = CFPreferencesCopyValue("AppleLanguages" as CFString, kCFPreferencesAnyApplication, kCFPreferencesCurrentUser, kCFPreferencesAnyHost) as? [String] ?? []
} else {
languages = CFPreferencesCopyAppValue("AppleLanguages" as CFString, kCFPreferencesCurrentApplication) as? [String] ?? []
}

return languages.compactMap {
Locale.canonicalLanguageIdentifier(from: $0)
}
}

func preferredLocale() -> String? {
guard let preferredLocaleID = CFPreferencesCopyAppValue("AppleLocale" as CFString, kCFPreferencesCurrentApplication) as? String else {
return nil
Expand All @@ -288,29 +298,29 @@ struct LocaleCache : Sendable, ~Copyable {
func preferredLanguages(forCurrentUser: Bool) -> [String] {
[Locale.canonicalLanguageIdentifier(from: "en-001")]
}

func preferredLocale() -> String? {
"en_001"
}
#endif

#if FOUNDATION_FRAMEWORK && !NO_CFPREFERENCES
/// This returns an instance of `Locale` that's set up exactly like it would be if the user changed the current locale to that identifier, set the preferences keys in the overrides dictionary, then called `current`.
func localeAsIfCurrent(name: String?, cfOverrides: CFDictionary? = nil, disableBundleMatching: Bool = false) -> Locale {

var (prefs, _) = preferences()
if let cfOverrides { prefs.apply(cfOverrides) }

let inner = _LocaleICU(name: name, prefs: prefs, disableBundleMatching: disableBundleMatching)
return Locale(inner: inner)
}
#endif

/// This returns an instance of `Locale` that's set up exactly like it would be if the user changed the current locale to that identifier, set the preferences keys in the overrides dictionary, then called `current`.
func localeAsIfCurrent(name: String?, overrides: LocalePreferences? = nil, disableBundleMatching: Bool = false) -> Locale {
var (prefs, _) = preferences()
if let overrides { prefs.apply(overrides) }

let inner = _localeICUClass().init(name: name, prefs: prefs, disableBundleMatching: disableBundleMatching)
return Locale(inner: inner)
}
Expand All @@ -334,7 +344,7 @@ struct LocaleCache : Sendable, ~Copyable {

let preferredLanguages = preferredLanguages(forCurrentUser: false)
guard let preferredLocaleID = preferredLocale() else { return nil }

let canonicalizedLocalizations = availableLocalizations.compactMap { Locale.canonicalLanguageIdentifier(from: $0) }
let identifier = Locale.localeIdentifierForCanonicalizedLocalizations(canonicalizedLocalizations, preferredLanguages: preferredLanguages, preferredLocaleID: preferredLocaleID)
guard let identifier else {
Expand Down