Use the filesystem tzdb for Darwin

Author: dkhalanskyjb

core/build.gradle.kts

@@ -155,7 +155,12 @@ kotlin {
                 // do nothing special
             }
             konanTarget.family.isAppleFamily -> {
-                // do nothing special
+                compilations["main"].cinterops {
+                    create("declarations") {
+                        defFile("$projectDir/darwin/cinterop/definitions.def")
+                        headers("$projectDir/darwin/cinterop/definitions.h")
+                    }
+                }
             }
             else -> {
                 throw IllegalArgumentException("Unknown native target ${this@withType}")

core/common/test/TimeZoneTest.kt

@@ -46,15 +46,24 @@ class TimeZoneTest {
 
     @Test
     fun availableZonesAreAvailable() {
+        val availableZones = mutableListOf<String>()
+        val nonAvailableZones = mutableListOf<Pair<String, Exception>>()
         for (zoneName in TimeZone.availableZoneIds) {
             val timezone = try {
                 TimeZone.of(zoneName)
             } catch (e: Exception) {
-                throw Exception("Zone $zoneName is not available", e)
+                nonAvailableZones.add(zoneName to e)
+                continue
             }
+            availableZones.add(zoneName)
             Instant.DISTANT_FUTURE.toLocalDateTime(timezone).toInstant(timezone)
             Instant.DISTANT_PAST.toLocalDateTime(timezone).toInstant(timezone)
         }
+        if (nonAvailableZones.isNotEmpty()) {
+            println("Available zones: $availableZones")
+            println("Non-available zones: $nonAvailableZones")
+            throw nonAvailableZones[0].second
+        }
     }
 
     @Test

core/darwin/cinterop/definitions.def

@@ -0,0 +1 @@
+package = kotlinx.datetime.internal

core/darwin/cinterop/definitions.h

@@ -0,0 +1,9 @@
+#include <stdbool.h>
+
+const bool kotlinxDatetimeRunningInSimulator =
+  #if TARGET_OS_SIMULATOR
+      true
+  #else
+      false
+  #endif
+;

core/darwin/src/Converters.kt

@@ -42,7 +42,7 @@ public fun NSDate.toKotlinInstant(): Instant {
  *
  * If the time zone is represented as a fixed number of seconds from UTC+0 (for example, if it is the result of a call
  * to [TimeZone.offset]) and the offset is not given in even minutes but also includes seconds, this method throws
- * [DateTimeException] to denote that lossy conversion would happen, as Darwin internally rounds the offsets to the
+ * [IllegalArgumentException] to denote that lossy conversion would happen, as Darwin internally rounds the offsets to the
  * nearest minute.
  */
 public fun TimeZone.toNSTimeZone(): NSTimeZone = if (this is FixedOffsetTimeZone) {
@@ -51,7 +51,8 @@ public fun TimeZone.toNSTimeZone(): NSTimeZone = if (this is FixedOffsetTimeZone
     }
     NSTimeZone.timeZoneForSecondsFromGMT(offset.totalSeconds.convert())
 } else {
-    NSTimeZone.timeZoneWithName(id) ?: NSTimeZone.timeZoneWithAbbreviation(id)!!
+    NSTimeZone.timeZoneWithName(id) ?: NSTimeZone.timeZoneWithAbbreviation(id)
+        ?: throw IllegalArgumentException("The Foundation framework does not support the timezone '$id'")
 }
 
 /**

core/darwin/src/TimeZoneNative.kt

@@ -7,10 +7,65 @@
 
 package kotlinx.datetime
 
-import kotlinx.datetime.internal.Path
-import kotlinx.datetime.internal.TzdbOnFilesystem
+import kotlinx.datetime.internal.*
 import platform.Foundation.*
 
 internal actual fun currentTime(): Instant = NSDate.date().toKotlinInstant()
 
-internal actual val tzdbOnFilesystem = TzdbOnFilesystem(Path.fromString("/var/db/timezone/zoneinfo"))
+// iOS simulator needs a different path, hence the check. See https://github.com/HowardHinnant/date/pull/577
+@OptIn(kotlinx.cinterop.ExperimentalForeignApi::class)
+internal actual val tzdbOnFilesystem = TzdbOnFilesystem(Path.fromString(
+        if (kotlinxDatetimeRunningInSimulator) "/usr/share/zoneinfo" else "/var/db/timezone/zoneinfo"))
+
+internal actual fun currentSystemDefaultId(): String? {
+    /* The framework has its own cache of the system timezone. Calls to
+    [NSTimeZone systemTimeZone] do not reflect changes to the system timezone
+    and instead just return the cached value. Thus, to acquire the current
+    system timezone, first, the cache should be cleared.
+
+    This solution is not without flaws, however. In particular, resetting the
+    system timezone also resets the default timezone ([NSTimeZone default]) if
+    it's the same as the cached system timezone:
+
+        NSTimeZone.defaultTimeZone = [NSTimeZone
+            timeZoneWithName: [[NSTimeZone systemTimeZone] name]];
+        NSLog(@"%@", NSTimeZone.defaultTimeZone.name);
+        NSLog(@"Change the system time zone, then press Enter");
+        getchar();
+        [NSTimeZone resetSystemTimeZone];
+        NSLog(@"%@", NSTimeZone.defaultTimeZone.name); // will also change
+
+    This is a fairly marginal problem:
+        * It is only a problem when the developer deliberately sets the default
+          timezone to the region that just happens to be the one that the user
+          is in, and then the user moves to another region, and the app also
+          uses the system timezone.
+        * Since iOS 11, the significance of the default timezone has been
+          de-emphasized. In particular, it is not included in the API for
+          Swift: https://forums.swift.org/t/autoupdating-type-properties/4608/4
+
+    Another possible solution could involve using [NSTimeZone localTimeZone].
+    This is documented to reflect the current, uncached system timezone on
+    iOS 11 and later:
+    https://developer.apple.com/documentation/foundation/nstimezone/1387209-localtimezone
+    However:
+        * Before iOS 11, this was the same as the default timezone and did not
+          reflect the system timezone.
+        * Worse, on a Mac (10.15.5), I failed to get it to work as documented.
+              NSLog(@"%@", NSTimeZone.localTimeZone.name);
+              NSLog(@"Change the system time zone, then press Enter");
+              getchar();
+              // [NSTimeZone resetSystemTimeZone]; // uncomment to make it work
+              NSLog(@"%@", NSTimeZone.localTimeZone.name);
+          The printed strings are the same even if I wait for good 10 minutes
+          before pressing Enter, unless the line with "reset" is uncommented--
+          then the timezone is updated, as it should be. So, for some reason,
+          NSTimeZone.localTimeZone, too, is cached.
+          With no iOS device to test this on, it doesn't seem worth the effort
+          to avoid just resetting the system timezone due to one edge case
+          that's hard to avoid.
+    */
+    NSTimeZone.resetSystemTimeZone()
+    val zone = NSTimeZone.systemTimeZone
+    return zone.name
+}

core/linux/src/TimeZoneNative.kt

@@ -75,4 +75,7 @@ internal actual fun currentTime(): Instant = memScoped {
     }
 }
 
+internal actual fun currentSystemDefaultId(): String? =
+        pathToSystemDefault()?.second?.toString()
+
 internal actual val tzdbOnFilesystem = TzdbOnFilesystem(Path.fromString("/usr/share/zoneinfo"))

core/nix/src/TimeZoneNative.kt

@@ -7,9 +7,7 @@
 package kotlinx.datetime
 
 import kotlinx.cinterop.memScoped
-import kotlinx.datetime.internal.OffsetInfo
-import kotlinx.datetime.internal.TimeZoneRules
-import kotlinx.datetime.internal.TzdbOnFilesystem
+import kotlinx.datetime.internal.*
 
 internal expect val tzdbOnFilesystem: TzdbOnFilesystem
 
@@ -23,9 +21,9 @@ internal actual class RegionTimeZone(private val tzid: TimeZoneRules, actual ove
         }
 
         actual fun currentSystemDefault(): RegionTimeZone {
-            val zoneId = tzdbOnFilesystem.currentSystemDefault()?.second
+            val zoneId = currentSystemDefaultId()
                     ?: throw IllegalStateException("Failed to get the system timezone")
-            return of(zoneId.toString())
+            return of(zoneId)
         }
 
         actual val availableZoneIds: Set<String>
@@ -61,3 +59,5 @@ internal actual class RegionTimeZone(private val tzid: TimeZoneRules, actual ove
 
     actual override fun offsetAtImpl(instant: Instant): UtcOffset = tzid.infoAtInstant(instant)
 }
+
+internal expect fun currentSystemDefaultId(): String?

core/nix/src/internal/TzdbOnFilesystem.kt

@@ -18,21 +18,21 @@ internal class TzdbOnFilesystem(defaultTzdbPath: Path) {
         tzdbPath.traverseDirectory(exclude = tzdbUnneededFiles) { add(it.toString()) }
     }
 
-    internal fun currentSystemDefault(): Pair<Path, Path>? {
-        val info = Path(true, listOf("etc", "localtime")).readLink() ?: return null
-        val i = info.components.indexOf("zoneinfo")
-        if (!info.isAbsolute || i == -1 || i == info.components.size - 1) return null
-        return Pair(
-            Path(true, info.components.subList(0, i + 1)),
-            Path(false, info.components.subList(i + 1, info.components.size))
-        )
-    }
-
     private val tzdbPath = defaultTzdbPath.check()?.let { defaultTzdbPath }
-        ?: currentSystemDefault()?.first ?: throw IllegalStateException("Could not find the path to the timezone database")
+        ?: pathToSystemDefault()?.first ?: throw IllegalStateException("Could not find the path to the timezone database")
 
 }
 
+internal fun pathToSystemDefault(): Pair<Path, Path>? {
+    val info = Path(true, listOf("etc", "localtime")).readLink() ?: return null
+    val i = info.components.indexOf("zoneinfo")
+    if (!info.isAbsolute || i == -1 || i == info.components.size - 1) return null
+    return Pair(
+            Path(true, info.components.subList(0, i + 1)),
+            Path(false, info.components.subList(i + 1, info.components.size))
+    )
+}
+
 private val tzdbUnneededFiles = setOf(
     "posix",
     "posixrules",