rdar://108022482 (Do more to cache Swift Locales bridged to Objective-C) (#29)

Author: parkera

Sources/FoundationInternationalization/Locale/Locale_Cache.swift

@@ -33,7 +33,8 @@ struct LocaleCache : Sendable {
         private var cachedCurrentNSLocale: _NSSwiftLocale!
         private var cachedAutoupdatingNSLocale: _NSSwiftLocale!
         private var cachedSystemNSLocale: _NSSwiftLocale!
-        private var cachedFixedNSLocales: [String : _NSSwiftLocale] = [:]
+        private var cachedFixedIdentifierToNSLocales: [String : _NSSwiftLocale] = [:]
+        private var cachedFixedLocaleToNSLocales: [_Locale : _NSSwiftLocale] = [:]
 #endif
 
         private var noteCount = -1
@@ -95,16 +96,28 @@ struct LocaleCache : Sendable {
 
 #if FOUNDATION_FRAMEWORK
         mutating func fixedNSLocale(_ id: String) -> _NSSwiftLocale {
-            if let locale = cachedFixedNSLocales[id] {
+            if let locale = cachedFixedIdentifierToNSLocales[id] {
                 return locale
             } else {
                 let inner = Locale(inner: fixed(id))
                 let locale = _NSSwiftLocale(inner)
                 // We have found ObjC clients that rely upon an immortal lifetime for these `Locale`s, so we do not clear this cache.
-                cachedFixedNSLocales[id] = locale
+                cachedFixedIdentifierToNSLocales[id] = locale
                 return locale
             }
         }
+        
+        mutating func fixedNSLocale(_ locale: _Locale) -> _NSSwiftLocale {
+            if let locale = cachedFixedLocaleToNSLocales[locale] {
+                return locale
+            } else {
+                let inner = Locale(inner: locale)
+                let nsLocale = _NSSwiftLocale(inner)
+                // We have found ObjC clients that rely upon an immortal lifetime for these `Locale`s, so we do not clear this cache.
+                cachedFixedLocaleToNSLocales[locale] = nsLocale
+                return nsLocale
+            }
+        }
 
         mutating func currentNSLocale(preferences: LocalePreferences?, cache: Bool) -> _NSSwiftLocale? {
             resetCurrentIfNeeded()
@@ -228,6 +241,10 @@ struct LocaleCache : Sendable {
         lock.withLock { $0.fixedNSLocale(id) }
     }
 
+    func fixedNSLocale(_ locale: _Locale) -> _NSSwiftLocale {
+        lock.withLock { $0.fixedNSLocale(locale) }
+    }
+
     func autoupdatingCurrentNSLocale() -> _NSSwiftLocale {
         lock.withLock { $0.autoupdatingNSLocale() }
     }

Sources/FoundationInternationalization/Locale/Locale_Wrappers.swift

@@ -673,8 +673,10 @@ extension Locale : _ObjectiveCBridgeable {
     @_semantics("convertToObjectiveC")
     public func _bridgeToObjectiveC() -> NSLocale {
         switch kind {
-        case .autoupdating, .fixed(_):
-            return _NSSwiftLocale(self)
+        case .autoupdating:
+            return LocaleCache.cache.autoupdatingCurrentNSLocale()
+        case .fixed(let l):
+            return LocaleCache.cache.fixedNSLocale(l)
         case .bridged(let wrapper):
             return wrapper._wrapped
         }

Tests/FoundationInternationalizationTests/LocaleTests.swift

@@ -512,7 +512,47 @@ final class LocalBridgingTests : XCTestCase {
         XCTAssertNotEqual(anyHashables[0], anyHashables[1])
         XCTAssertEqual(anyHashables[1], anyHashables[2])
     }
+    
+    func test_autoupdatingBridge() {
+        let s1 = Locale.autoupdatingCurrent
+        let s2 = Locale.autoupdatingCurrent
+        let ns1 = s1 as NSLocale
+        let ns2 = s2 as NSLocale
+        // Verify that we don't create a new instance each time this is converted to NSLocale
+        XCTAssertTrue(ns1 === ns2)
+    }
+    
+    func test_bridgingTwice() {
+        let s1 = NSLocale.system
+        let l1 = s1 as Locale
+        let s2 = NSLocale.system
+        let l2 = s2 as Locale
+        XCTAssertTrue(l1 as NSLocale === l2 as NSLocale)
+    }
+    
+    func test_bridgingFixedTwice() {
+        let s1 = Locale(identifier: "en_US")
+        let ns1 = s1 as NSLocale
+        let s2 = Locale(identifier: "en_US")
+        let ns2 = s2 as NSLocale
+        XCTAssertTrue(ns1 === ns2)
+    }
+    
+    func test_bridgingCurrentWithPrefs() {
+        // Verify that 'current with prefs' locales (which have identical identifiers but differing prefs) are correctly cached
+        let s1 = Locale.localeAsIfCurrent(name: "en_US", overrides: .init(metricUnits: true), disableBundleMatching: false)
+        let ns1 = s1 as NSLocale
+        let s2 = Locale.localeAsIfCurrent(name: "en_US", overrides: .init(metricUnits: true), disableBundleMatching: false)
+        let ns2 = s2 as NSLocale
+        let s3 = Locale.localeAsIfCurrent(name: "en_US", overrides: .init(measurementUnits: .centimeters), disableBundleMatching: false)
+        let ns3 = s3 as NSLocale
+        
+        XCTAssertTrue(ns1 === ns2)
+        XCTAssertTrue(ns1 !== ns3)
+        XCTAssertTrue(ns2 !== ns3)
+    }
 }
+
 #endif // FOUNDATION_FRAMEWORK
 
 // MARK: - FoundationPreview Disabled Tests