More robustly search for zoneinfo directories

Author: dkhalanskyjb

core/darwinDevices/src/internal/TimeZoneNative.kt

@@ -5,4 +5,4 @@
 
 package kotlinx.datetime.internal
 
-internal actual fun getTzdbPath(): Path = Path.fromString("/var/db/timezone/zoneinfo")
+internal actual fun defaultTzdbPath(): String? = "/var/db/timezone/zoneinfo"

core/darwinSimulator/src/internal/TimeZoneNative.kt

@@ -5,4 +5,4 @@
 
 package kotlinx.datetime.internal
 
-internal actual fun getTzdbPath(): Path = Path.fromString("/usr/share/zoneinfo.default")
+internal actual fun defaultTzdbPath(): String? = "/usr/share/zoneinfo.default"

core/linux/src/internal/TimeZoneNative.kt

@@ -11,18 +11,4 @@ internal actual fun currentSystemDefaultZone(): RegionTimeZone {
     return RegionTimeZone(systemTzdb.rulesForId(zoneId), zoneId)
 }
 
-internal actual fun getTzdbPath(): Path {
-    val defaultPath = Path.fromString("/usr/share/zoneinfo")
-    return defaultPath.check()?.let { defaultPath }
-            ?: pathToSystemDefault()?.first ?: throw IllegalStateException("Could not find the path to the timezone database")
-}
-
-private 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))
-    )
-}
+internal actual fun defaultTzdbPath(): String? = null

core/nix/src/internal/TimeZoneNative.kt

@@ -5,8 +5,6 @@
 
 package kotlinx.datetime.internal
 
-import kotlinx.datetime.*
-
 internal class TzdbOnFilesystem(val tzdbPath: Path): TimezoneDatabase {
 
     override fun rulesForId(id: String): TimeZoneRules =
@@ -18,16 +16,49 @@ internal class TzdbOnFilesystem(val tzdbPath: Path): TimezoneDatabase {
 
 }
 
+/** The files that sometimes lie in the `zoneinfo` directory but aren't actually time zones. */
 private val tzdbUnneededFiles = setOf(
+    // taken from https://github.com/tzinfo/tzinfo/blob/9953fc092424d55deaea2dcdf6279943f3495724/lib/tzinfo/data_sources/zoneinfo_data_source.rb#L88C29-L97C21
+    "+VERSION",
+    "leapseconds",
+    "localtime",
     "posix",
     "posixrules",
+    "right",
+    "SECURITY",
+    "src",
+    "timeconfig",
+    // taken from https://github.com/HowardHinnant/date/blob/ab37c362e35267d6dee02cb47760f9e9c669d3be/src/tz.cpp#L2863-L2874
     "Factory",
     "iso3166.tab",
-    "right",
-    "+VERSION",
     "zone.tab",
     "zone1970.tab",
     "tzdata.zi",
-    "leapseconds",
     "leap-seconds.list"
 )
+
+/** If the platform has a preference for a specific timezone database path, this field contains it. */
+internal expect fun defaultTzdbPath(): String?
+
+/** The directories checked for a valid timezone database. */
+private val tzdbPaths = sequence {
+    defaultTzdbPath()?.let { yield(Path.fromString(it)) }
+    // taken from https://github.com/tzinfo/tzinfo/blob/9953fc092424d55deaea2dcdf6279943f3495724/lib/tzinfo/data_sources/zoneinfo_data_source.rb#L70
+    yieldAll(listOf("/usr/share/zoneinfo", "/usr/share/lib/zoneinfo", "/etc/zoneinfo").map { Path.fromString(it) })
+    pathToSystemDefault()?.first?.let { yield(it) }
+}
+
+// taken from https://github.com/HowardHinnant/date/blob/ab37c362e35267d6dee02cb47760f9e9c669d3be/src/tz.cpp#L3951-L3952
+internal fun pathToSystemDefault(): Pair<Path, Path>? {
+    val info = Path(true, listOf("etc", "localtime")).chaseSymlinks().first
+    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))
+    )
+}
+
+internal actual val systemTzdb: TimezoneDatabase = tzdbPaths.find {
+    it.chaseSymlinks().second?.isDirectory == true
+}?.let { TzdbOnFilesystem(it) } ?: throw IllegalStateException("Could not find the path to the timezone database")

core/nix/src/internal/TzdbOnFilesystem.kt

@@ -3,7 +3,7 @@
  * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
  */
 
-@file:OptIn(kotlinx.cinterop.ExperimentalForeignApi::class)
+@file:OptIn(ExperimentalForeignApi::class)
 package kotlinx.datetime.internal
 
 import kotlinx.cinterop.*
@@ -15,8 +15,8 @@ internal class Path(val isAbsolute: Boolean, val components: List<String>) {
         val err = stat(this@Path.toString(), stat.ptr)
         if (err != 0) return null
         object : PathInfo {
-            override val isDirectory: Boolean = stat.st_mode.toInt() and S_IFMT == S_IFDIR // `inode(7)`, S_ISDIR
-            override val isSymlink: Boolean = stat.st_mode.toInt() and S_IFMT == S_IFLNK // `inode(7)`, S_ISLNK
+            override val isDirectory: Boolean get() = stat.st_mode.toInt() and S_IFMT == S_IFDIR // `inode(7)`, S_ISDIR
+            override val isSymlink: Boolean get() = stat.st_mode.toInt() and S_IFMT == S_IFLNK // `inode(7)`, S_ISLNK
         }
     }
 
@@ -53,6 +53,17 @@ internal class Path(val isAbsolute: Boolean, val components: List<String>) {
     }
 }
 
+internal fun Path.chaseSymlinks(): Pair<Path, PathInfo?> {
+    var realPath = this
+    var stat: PathInfo? = realPath.check()
+    while (stat?.isSymlink == true) {
+        stat = null
+        realPath = realPath.readLink() ?: break
+        stat = realPath.check() ?: break
+    }
+    return realPath to stat
+}
+
 // `stat(2)` lists the other available fields
 internal interface PathInfo {
     val isDirectory: Boolean