TimeZone, Calendar, and Locale disagree on how .current is serialized (#1491)

* (157160558) TimeZone, Calendar, and Locale disagree on how .current is encoded

* Revert roundtripEncoding back to its original state

* Address feedback

Author: jmschonfeld

Sources/FoundationEssentials/Calendar/Calendar.swift

@@ -1616,19 +1616,12 @@ extension Calendar : Codable {
     public init(from decoder: Decoder) throws {
         let container = try decoder.container(keyedBy: CodingKeys.self)
 
-        if let current = try container.decodeIfPresent(Current.self, forKey: .current) {
-            switch current {
-            case .autoupdatingCurrent:
-                self = Calendar.autoupdatingCurrent
-                return
-            case .current:
-                self = Calendar.current
-                return
-            case .fixed:
-                // Fall through to identifier-based
-                break
-            }
+        if let current = try container.decodeIfPresent(Current.self, forKey: .current), current == .autoupdatingCurrent {
+            self = Calendar.autoupdatingCurrent
+            return
         }
+        
+        // Just like TimeZone and Locale, Whether the calendar was fixed or current we decode as a fixed calendar if it wasn't encoded as the sentinel autoupdating current
 
         let identifierString = try container.decode(String.self, forKey: .identifier)
         // Same as NSCalendar.Identifier
@@ -1655,7 +1648,8 @@ extension Calendar : Codable {
         try container.encode(self.firstWeekday, forKey: .firstWeekday)
         try container.encode(self.minimumDaysInFirstWeek, forKey: .minimumDaysInFirstWeek)
 
-        // current and autoupdatingCurrent are sentinel values. Calendar could theoretically not treat 'current' as a sentinel, but it is required for Locale (one of the properties of Calendar), so transitively we have to do the same here
+        // autoupdatingCurrent is a sentinel value
+        // Prior to FoundationPreview 6.3 releases, Calendar treated current-equivalent calendars as sentinel values while decoding as well. As of FoundationPreview 6.2 releases, Calendar no longer decodes the current sentinel value, but it is still encoded to preserve behavior when decoding with older runtimes
         if self == Calendar.autoupdatingCurrent {
             try container.encode(Current.autoupdatingCurrent, forKey: .current)
         } else if self == Calendar.current {

Sources/FoundationEssentials/Locale/Locale.swift

@@ -94,6 +94,10 @@ public struct Locale : Hashable, Equatable, Sendable {
         // On Darwin, this overrides are applied on top of CFPreferences.
         return LocaleCache.cache.localeAsIfCurrent(name: name, overrides: overrides, disableBundleMatching: disableBundleMatching)
     }
+    
+    internal static func localeWithPreferences(identifier: String, preferences: LocalePreferences) -> Locale {
+        return LocaleCache.cache.localeWithPreferences(identifier: identifier, prefs: preferences)
+    }
 
     internal static func localeAsIfCurrentWithBundleLocalizations(_ availableLocalizations: [String], allowsMixedLocalizations: Bool) -> Locale? {
         return LocaleCache.cache.localeAsIfCurrentWithBundleLocalizations(availableLocalizations, allowsMixedLocalizations: allowsMixedLocalizations)
@@ -814,6 +818,7 @@ extension Locale : Codable {
     private enum CodingKeys : Int, CodingKey {
         case identifier
         case current
+        case preferences
     }
 
     // CFLocale enforces a rule that fixed/current/autoupdatingCurrent can never be equal even if their values seem like they are the same
@@ -825,23 +830,35 @@ extension Locale : Codable {
 
     public init(from decoder: Decoder) throws {
         let container = try decoder.container(keyedBy: CodingKeys.self)
+        let prefs = try container.decodeIfPresent(LocalePreferences.self, forKey: .preferences)
 
         if let current = try container.decodeIfPresent(Current.self, forKey: .current) {
             switch current {
             case .autoupdatingCurrent:
                 self = Locale.autoupdatingCurrent
                 return
             case .current:
-                self = Locale.current
-                return
+                if prefs == nil {
+                    // Prior to FoundationPreview 6.3 releases, Locale did not encode preferences and expected decoding .current to decode with the new current user's preferences via the new process' .currrent locale
+                    // Preserve behavior for encoded current locales without encoded preferences by decoding as the current locale here to preserve the intent of including user preferences even though preferences are not included in the archive
+                    // If preferences were encoded (the current locale encoded from a post-FoundationPreview 6.3 release), fallthrough to the new behavior below
+                    self = Locale.current
+                    return
+                }
             case .fixed:
                 // Fall through to identifier-based
                 break
             }
         }
 
         let identifier = try container.decode(String.self, forKey: .identifier)
-        self.init(identifier: identifier)
+        if let prefs {
+            // If preferences were encoded, create a locale with the preferences and identifier (not including preferences from the current user)
+            self = Locale.localeWithPreferences(identifier: identifier, preferences: prefs)
+        } else {
+            // If no preferences were encoded, create a fixed locale with just the identifier
+            self.init(identifier: identifier)
+        }
     }
 
     public func encode(to encoder: Encoder) throws {
@@ -852,9 +869,15 @@ extension Locale : Codable {
         if self == Locale.autoupdatingCurrent {
             try container.encode(Current.autoupdatingCurrent, forKey: .current)
         } else if self == Locale.current {
+            // Always encode .current for the current locale to preserve existing decoding behavior of .current when decoding on older runtimes prior to FoundationPreview 6.3 releases
             try container.encode(Current.current, forKey: .current)
         } else {
             try container.encode(Current.fixed, forKey: .current)
         }
+        
+        if let prefs {
+            // Encode preferences (if present) so that when decoding on newer runtimes (FoundationPreview 6.3 releases and later) we create a locale with the preferences as they are at encode time
+            try container.encode(prefs, forKey: .preferences)
+        }
     }
 }

Sources/FoundationEssentials/Locale/Locale_Preferences.swift

@@ -17,7 +17,7 @@ internal import _ForSwiftFoundation
 
 /// Holds user preferences about `Locale`, retrieved from user defaults. It is only used when creating the `current` Locale. Fixed-identifier locales never have preferences.
 package struct LocalePreferences: Hashable, Sendable {
-    package enum MeasurementUnit {
+    package enum MeasurementUnit: Int, Codable {
         case centimeters
         case inches
 
@@ -38,7 +38,7 @@ package struct LocalePreferences: Hashable, Sendable {
         }
     }
 
-    package enum TemperatureUnit {
+    package enum TemperatureUnit: Int, Codable {
         case fahrenheit
         case celsius
 
@@ -66,7 +66,7 @@ package struct LocalePreferences: Hashable, Sendable {
     package var firstWeekday: [Calendar.Identifier : Int]?
     package var minDaysInFirstWeek: [Calendar.Identifier : Int]?
 #if FOUNDATION_FRAMEWORK
-    struct ICUSymbolsAndStrings : Hashable, @unchecked Sendable {
+    package struct ICUSymbolsAndStrings : Hashable, @unchecked Sendable {
         // The following `CFDictionary` ivars are used directly by `CFDateFormatter`. Keep them as `CFDictionary` to avoid bridging them into and out of Swift. We don't need to access them from Swift at all.
 
         package var icuDateTimeSymbols: CFDictionary?
@@ -91,6 +91,8 @@ package struct LocalePreferences: Hashable, Sendable {
     package var temperatureUnit: TemperatureUnit?
     package var force24Hour: Bool?
     package var force12Hour: Bool?
+    
+    // Note: When adding new preferences, be sure to include them in the serialized format via the Codable conformance below
 
     package init() { }
 
@@ -108,7 +110,8 @@ package struct LocalePreferences: Hashable, Sendable {
          force24Hour: Bool? = nil,
          force12Hour: Bool? = nil,
          numberSymbols: [UInt32 : String]? = nil,
-         dateFormats: [Date.FormatStyle.DateStyle: String]? = nil) {
+         dateFormats: [Date.FormatStyle.DateStyle: String]? = nil,
+         icuSymbolsAndStrings: ICUSymbolsAndStrings = ICUSymbolsAndStrings()) {
 
         self.metricUnits = metricUnits
         self.languages = languages
@@ -123,6 +126,7 @@ package struct LocalePreferences: Hashable, Sendable {
         self.force12Hour = force12Hour
         self.numberSymbols = numberSymbols
         self.dateFormats = dateFormats
+        self.icuSymbolsAndStrings = icuSymbolsAndStrings
     }
 #else
     package init(metricUnits: Bool? = nil,
@@ -331,3 +335,192 @@ package struct LocalePreferences: Hashable, Sendable {
         }
     }
 }
+
+extension LocalePreferences: Codable {
+    private enum CodingKeys: String, CodingKey {
+        case metricUnits = "metric"
+        case languages = "langs"
+        case locale
+        case collationOrder = "coll"
+        case firstWeekday = "weekFirst"
+        case minDaysInFirstWeek = "weekMin"
+        case icuSymbolsAndStrings = "icu"
+        case dateFormats = "dates"
+        case numberSymbols = "nums"
+        case country
+        case measurementUnits = "meas"
+        case temperatureUnit = "temp"
+        case force24Hour = "24h"
+        case force12Hour = "12h"
+    }
+    
+    package func encode(to encoder: any Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encodeIfPresent(metricUnits, forKey: .metricUnits)
+        try container.encodeIfPresent(languages, forKey: .languages)
+        try container.encodeIfPresent(locale, forKey: .locale)
+        try container.encodeIfPresent(collationOrder, forKey: .collationOrder)
+        let firstWeekdayMapped = self.firstWeekday.map {
+            var result = [String : Int]()
+            for (identifier, day) in $0 {
+                result[identifier.cfCalendarIdentifier] = day
+            }
+            return result
+        }
+        try container.encodeIfPresent(firstWeekdayMapped, forKey: .firstWeekday)
+        let minDaysInFirstWeekMapped = self.minDaysInFirstWeek.map {
+            var result = [String : Int]()
+            for (identifier, days) in $0 {
+                result[identifier.cldrIdentifier] = days
+            }
+            return result
+        }
+        try container.encodeIfPresent(minDaysInFirstWeekMapped, forKey: .minDaysInFirstWeek)
+#if FOUNDATION_FRAMEWORK
+        if icuSymbolsAndStrings.containsValuesToSerialize {
+            try container.encodeIfPresent(icuSymbolsAndStrings, forKey: .icuSymbolsAndStrings)
+        }
+#if !NO_FORMATTERS
+        try container.encodeIfPresent(dateFormats.map {
+            var result = [UInt : String]()
+            for (format, value) in $0 {
+                result[format.rawValue] = value
+            }
+            return result
+        }, forKey: .dateFormats)
+#endif
+#endif
+        try container.encodeIfPresent(numberSymbols, forKey: .numberSymbols)
+        try container.encodeIfPresent(country, forKey: .country)
+        try container.encodeIfPresent(measurementUnits, forKey: .measurementUnits)
+        try container.encodeIfPresent(temperatureUnit, forKey: .temperatureUnit)
+        try container.encodeIfPresent(force24Hour, forKey: .force24Hour)
+        try container.encodeIfPresent(force12Hour, forKey: .force12Hour)
+    }
+    
+    package init(from decoder: any Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        let metricUnits = try container.decodeIfPresent(Bool.self, forKey: .metricUnits)
+        let languages = try container.decodeIfPresent([String].self, forKey: .languages)
+        let locale = try container.decodeIfPresent(String.self, forKey: .locale)
+        let collationOrder = try container.decodeIfPresent(String.self, forKey: .collationOrder)
+        let firstWeekday = try container.decodeIfPresent([String : Int].self, forKey: .firstWeekday).map {
+            var result = [Calendar.Identifier : Int]()
+            for (stringIdentifier, day) in $0 {
+                guard let identifier = Calendar.Identifier(identifierString: stringIdentifier) else {
+                    throw DecodingError.dataCorruptedError(forKey: .firstWeekday, in: container, debugDescription: "Unknown calendar identifier '\(stringIdentifier)'")
+                }
+                result[identifier] = day
+            }
+            return result
+        }
+        let minDaysInFirstWeek = try container.decodeIfPresent([String : Int].self, forKey: .minDaysInFirstWeek).map {
+            var result = [Calendar.Identifier : Int]()
+            for (stringIdentifier, days) in $0 {
+                guard let identifier = Calendar.Identifier(identifierString: stringIdentifier) else {
+                    throw DecodingError.dataCorruptedError(forKey: .minDaysInFirstWeek, in: container, debugDescription: "Unknown calendar identifier '\(stringIdentifier)'")
+                }
+                result[identifier] = days
+            }
+            return result
+        }
+        let country = try container.decodeIfPresent(String.self, forKey: .country)
+        let measurementUnits = try container.decodeIfPresent(MeasurementUnit.self, forKey: .measurementUnits)
+        let temperatureUnit = try container.decodeIfPresent(TemperatureUnit.self, forKey: .temperatureUnit)
+        let force24Hour = try container.decodeIfPresent(Bool.self, forKey: .force24Hour)
+        let force12Hour = try container.decodeIfPresent(Bool.self, forKey: .force12Hour)
+        let numberSymbols = try container.decodeIfPresent([UInt32 : String].self, forKey: .numberSymbols)
+        
+        #if FOUNDATION_FRAMEWORK && !NO_FORMATTERS
+        let dateFormats = try container.decodeIfPresent([UInt: String].self, forKey: .dateFormats).map {
+            var result = [Date.FormatStyle.DateStyle : String]()
+            for (rawValue, format) in $0 {
+                result[Date.FormatStyle.DateStyle(rawValue: rawValue)] = format
+            }
+            return result
+        }
+        let icuDateFormats = dateFormats.map {
+            var cfResult = [String : String]()
+            for (style, format) in $0 {
+                cfResult["\(style.rawValue)"] = format
+            }
+            return cfResult as CFDictionary
+        }
+        let icuNumberSymbols = numberSymbols.map {
+            var result = [String : String]()
+            for (rawValue, symbol) in $0 {
+                result["\(rawValue)"] = symbol
+            }
+            return result as CFDictionary
+        }
+        var icuSymbolsAndStrings = try container.decodeIfPresent(ICUSymbolsAndStrings.self, forKey: .icuSymbolsAndStrings) ?? ICUSymbolsAndStrings()
+        icuSymbolsAndStrings.icuDateFormatStrings = icuDateFormats
+        icuSymbolsAndStrings.icuNumberSymbols = icuNumberSymbols
+        
+        self.init(
+            metricUnits: metricUnits,
+            languages: languages,
+            locale: locale,
+            collationOrder: collationOrder,
+            firstWeekday: firstWeekday,
+            minDaysInFirstWeek: minDaysInFirstWeek,
+            country: country,
+            measurementUnits: measurementUnits,
+            temperatureUnit: temperatureUnit,
+            force24Hour: force24Hour,
+            force12Hour: force12Hour,
+            numberSymbols: numberSymbols,
+            dateFormats: dateFormats,
+            icuSymbolsAndStrings: icuSymbolsAndStrings
+        )
+        #else
+        self.init(
+            metricUnits: metricUnits,
+            languages: languages,
+            locale: locale,
+            collationOrder: collationOrder,
+            firstWeekday: firstWeekday,
+            minDaysInFirstWeek: minDaysInFirstWeek,
+            country: country,
+            measurementUnits: measurementUnits,
+            temperatureUnit: temperatureUnit,
+            force24Hour: force24Hour,
+            force12Hour: force12Hour,
+            numberSymbols: numberSymbols
+        )
+        #endif
+    }
+}
+
+#if FOUNDATION_FRAMEWORK
+extension LocalePreferences.ICUSymbolsAndStrings: Codable {
+    var containsValuesToSerialize: Bool {
+        icuDateTimeSymbols != nil || icuTimeFormatStrings != nil || icuNumberFormatStrings != nil
+    }
+    
+    private enum CodingKeys: String, CodingKey {
+        case icuDateTimeSymbols = "dtSym"
+        case icuTimeFormatStrings = "times"
+        case icuNumberFormatStrings = "nums"
+    }
+    
+    package func encode(to encoder: any Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encodeIfPresent(icuDateTimeSymbols.map { $0 as? [String : [String]] }, forKey: .icuDateTimeSymbols)
+        try container.encodeIfPresent(icuTimeFormatStrings.map { $0 as? [String : String] }, forKey: .icuTimeFormatStrings)
+        try container.encodeIfPresent(icuNumberFormatStrings.map { $0 as? [String : String] }, forKey: .icuNumberFormatStrings)
+    }
+    
+    package init(from decoder: any Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        
+        self.icuDateTimeSymbols = try container.decodeIfPresent([String : [String]].self, forKey: .icuDateTimeSymbols).map { $0 as CFDictionary }
+        self.icuTimeFormatStrings = try container.decodeIfPresent([String : String].self, forKey: .icuTimeFormatStrings).map { $0 as CFDictionary }
+        self.icuNumberFormatStrings = try container.decodeIfPresent([String : String].self, forKey: .icuNumberFormatStrings).map { $0 as CFDictionary }
+        
+        // Will be filled in by LocalePreferences serialized value
+        self.icuDateFormatStrings = nil
+        self.icuNumberSymbols = nil
+    }
+}
+#endif

Sources/FoundationEssentials/TimeZone/TimeZone.swift

@@ -335,6 +335,9 @@ extension TimeZone : Codable {
         var container = encoder.container(keyedBy: CodingKeys.self)
         // Even if we are autoupdatingCurrent, encode the identifier for backward compatibility
         try container.encode(self.identifier, forKey: .identifier)
+        
+        // Autoupdating current timezones are treated as sentinel values, but the current TimeZone is encoded as a fixed TimeZone
+        // This is the same behavior as Locale/Calendar except it did not previously encode as a sentinel value before FoundationPreview 6.3, so no extra key is encoded for the current time zone
         if _tz.isAutoupdating {
             try container.encode(true, forKey: .autoupdating)
         }

Sources/FoundationEssentials/TimeZone/TimeZone_Cache.swift

@@ -100,6 +100,13 @@ struct TimeZoneCache : Sendable, ~Copyable {
 #endif
             return oldTimeZone
         }
+        
+        mutating func resetCurrent(to newValue: TimeZone) {
+            currentTimeZone = newValue
+#if FOUNDATION_FRAMEWORK
+            bridgedCurrentTimeZone = nil
+#endif
+        }
 
         /// Reads from environment variables `TZFILE`, `TZ` and finally the symlink pointed at by the C macro `TZDEFAULT` to figure out what the current (aka "system") time zone is.
         mutating func findCurrentTimeZone() -> TimeZone {
@@ -398,6 +405,10 @@ struct TimeZoneCache : Sendable, ~Copyable {
     func reset() -> TimeZone? {
         return lock.withLock { $0.reset() }
     }
+    
+    func resetCurrent(to newValue: TimeZone) {
+        return lock.withLock { $0.resetCurrent(to: newValue) }
+    }
 
     var current: TimeZone {
         lock.withLock { $0.current() }