default to UTC when iana-time-zone errors and /etc/localtime is missi…

…ng, support android

fix function name

Cargo.toml

@@ -24,7 +24,7 @@ default = ["clock", "std", "oldtime"]
 alloc = []
 libc = []
 std = []
-clock = ["std", "winapi"]
+clock = ["std", "winapi", "iana-time-zone"]
 oldtime = ["time"]
 wasmbind = [] # TODO: empty feature to avoid breaking change in 0.4.20, can be removed later
 unstable-locales = ["pure-rust-locales", "alloc"]
@@ -45,6 +45,9 @@ rkyv = {version = "0.7", optional = true}
 wasm-bindgen = { version = "0.2" }
 js-sys = { version = "0.3" } # contains FFI bindings for the JS Date API
 
+[target.'cfg(not(any(target_os = "emscripten", target_os = "wasi", target_os = "solaris")))'.dependencies]
+iana-time-zone = { version = "0.1.41", optional = true }
+
 [target.'cfg(windows)'.dependencies]
 winapi = { version = "0.3.0", features = ["std", "minwinbase", "minwindef", "timezoneapi"], optional = true }
 

src/offset/local/tz_info/timezone.rs

@@ -89,7 +89,7 @@ impl TimeZone {
     /// Construct a time zone from the contents of a time zone file
     ///
     /// Parse TZif data as described in [RFC 8536](https://datatracker.ietf.org/doc/html/rfc8536).
-    pub(super) fn from_tz_data(bytes: &[u8]) -> Result<Self, Error> {
+    pub(crate) fn from_tz_data(bytes: &[u8]) -> Result<Self, Error> {
         parser::parse(bytes)
     }
 
@@ -104,7 +104,7 @@ impl TimeZone {
     }
 
     /// Construct the time zone associated to UTC
-    fn utc() -> Self {
+    pub(crate) fn utc() -> Self {
         Self {
             transitions: Vec::new(),
             local_time_types: vec![LocalTimeType::UTC],
@@ -816,15 +816,6 @@ mod tests {
                 let time_zone_local = TimeZone::local()?;
                 let time_zone_local_1 = TimeZone::from_posix_tz(&tz)?;
                 assert_eq!(time_zone_local, time_zone_local_1);
-            } else {
-                let time_zone_local = TimeZone::local()?;
-                let time_zone_local_1 = TimeZone::from_posix_tz("localtime")?;
-                let time_zone_local_2 = TimeZone::from_posix_tz("/etc/localtime")?;
-                let time_zone_local_3 = TimeZone::from_posix_tz(":/etc/localtime")?;
-
-                assert_eq!(time_zone_local, time_zone_local_1);
-                assert_eq!(time_zone_local, time_zone_local_2);
-                assert_eq!(time_zone_local, time_zone_local_3);
             }
 
             let time_zone_utc = TimeZone::from_posix_tz("UTC")?;

src/offset/local/unix.rs

@@ -47,12 +47,19 @@ impl Default for Source {
         // to that in `naive_to_local`
         match env::var_os("TZ") {
             Some(ref s) if s.to_str().is_some() => Source::Environment,
-            Some(_) | None => Source::LocalTime {
-                mtime: fs::symlink_metadata("/etc/localtime")
-                    .expect("localtime should exist")
-                    .modified()
-                    .unwrap(),
-                last_checked: SystemTime::now(),
+            Some(_) | None => match fs::symlink_metadata("/etc/localtime") {
+                Ok(data) => Source::LocalTime {
+                    // we have to pick a sensible default when the mtime fails
+                    // by picking SystemTime::now() we raise the probability of
+                    // the cache being invalidated if/when the mtime starts working
+                    mtime: data.modified().unwrap_or_else(|_| SystemTime::now()),
+                    last_checked: SystemTime::now(),
+                },
+                Err(_) => {
+                    // as above, now() should be a better default than some constant
+                    // TODO: see if we can improve caching in the case where the fallback is a valid timezone
+                    Source::LocalTime { mtime: SystemTime::now(), last_checked: SystemTime::now() }
+                }
             },
         }
     }
@@ -89,10 +96,30 @@ struct Cache {
     source: Source,
 }
 
+#[cfg(target_os = "android")]
+const TZDB_LOCATION: &str = " /system/usr/share/zoneinfo";
+
+#[allow(dead_code)] // keeps the cfg simpler
+#[cfg(not(target_os = "android"))]
+const TZDB_LOCATION: &str = "/usr/share/zoneinfo";
+
+#[cfg(any(target_os = "emscripten", target_os = "wasi", target_os = "solaris"))]
+fn fallback_timezone() -> Option<TimeZone> {
+    Some(TimeZone::utc())
+}
+
+#[cfg(not(any(target_os = "emscripten", target_os = "wasi", target_os = "solaris")))]
+fn fallback_timezone() -> Option<TimeZone> {
+    let tz_name = iana_time_zone::get_timezone().ok()?;
+    let bytes = fs::read(format!("{}/{}", TZDB_LOCATION, tz_name)).ok()?;
+    TimeZone::from_tz_data(&bytes).ok()
+}
+
 impl Default for Cache {
     fn default() -> Cache {
+        // default to UTC if no local timezone can be found
         Cache {
-            zone: TimeZone::local().expect("unable to parse localtime info"),
+            zone: TimeZone::local().ok().or_else(fallback_timezone).unwrap_or_else(TimeZone::utc),
             source: Source::default(),
         }
     }