default to UTC when /etc/localtime is missing

.github/workflows/test-release.yml

@@ -31,11 +31,11 @@ jobs:
           - os: ubuntu-latest
             rust_version: nightly
           - os: ubuntu-20.04
-            rust_version: 1.32.0
+            rust_version: 1.38.0
           - os: macos-latest
-            rust_version: 1.32.0
+            rust_version: 1.38.0
           - os: windows-latest
-            rust_version: 1.32.0
+            rust_version: 1.38.0
 
     runs-on: ${{ matrix.os }}
 

.github/workflows/test.yml

@@ -39,11 +39,11 @@ jobs:
           - os: ubuntu-latest
             rust_version: nightly
           - os: ubuntu-20.04
-            rust_version: 1.32.0
+            rust_version: 1.38.0
           - os: macos-latest
-            rust_version: 1.32.0
+            rust_version: 1.38.0
           - os: windows-latest
-            rust_version: 1.32.0
+            rust_version: 1.38.0
 
     runs-on: ${{ matrix.os }}
 

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 }
 

ci/github.sh

@@ -29,7 +29,7 @@ meaningful in the github actions feature matrix UI.
 
     runv cargo --version
 
-    if [[ ${RUST_VERSION:-} != 1.32.0 ]]; then
+    if [[ ${RUST_VERSION:-} != 1.38.0 ]]; then
         if [[ ${WASM:-} == yes_wasm ]]; then
             test_wasm
         elif [[ ${WASM:-} == wasm_simple ]]; then
@@ -49,7 +49,7 @@ meaningful in the github actions feature matrix UI.
         else
             test_regular UTC0
         fi
-    elif [[ ${RUST_VERSION:-} == 1.32.0 ]]; then
+    elif [[ ${RUST_VERSION:-} == 1.38.0 ]]; then
         test_132
     else
         echo "ERROR: didn't run any tests"

clippy.toml

@@ -1 +1 @@
-msrv = "1.32"
+msrv = "1.38"

src/format/mod.rs

@@ -529,7 +529,7 @@ fn format_inner<'a>(
             };
 
             if let Some(v) = v {
-                if (spec == &Year || spec == &IsoYear) && !(0 <= v && v < 10_000) {
+                if (spec == &Year || spec == &IsoYear) && !(0..10_000).contains(&v) {
                     // non-four-digit years require an explicit sign as per ISO 8601
                     match *pad {
                         Pad::None => write!(result, "{:+}", v),

src/format/parsed.rs

@@ -232,7 +232,7 @@ impl Parsed {
     /// given hour number in 12-hour clocks.
     #[inline]
     pub fn set_hour12(&mut self, value: i64) -> ParseResult<()> {
-        if value < 1 || value > 12 {
+        if !(1..=12).contains(&value) {
             return Err(OUT_OF_RANGE);
         }
         set_if_consistent(&mut self.hour_mod_12, value as u32 % 12)

src/format/scan.rs

@@ -48,7 +48,7 @@ pub(super) fn number(s: &str, min: usize, max: usize) -> ParseResult<(&str, i64)
     let mut n = 0i64;
     for (i, c) in bytes.iter().take(max).cloned().enumerate() {
         // cloned() = copied()
-        if c < b'0' || b'9' < c {
+        if !(b'0'..=b'9').contains(&c) {
             if i < min {
                 return Err(INVALID);
             } else {
@@ -79,7 +79,7 @@ pub(super) fn nanosecond(s: &str) -> ParseResult<(&str, i64)> {
     let v = v.checked_mul(SCALE[consumed]).ok_or(OUT_OF_RANGE)?;
 
     // if there are more than 9 digits, skip next digits.
-    let s = s.trim_left_matches(|c: char| '0' <= c && c <= '9');
+    let s = s.trim_left_matches(|c: char| ('0'..='9').contains(&c));
 
     Ok((s, v))
 }

src/naive/date.rs

@@ -1887,7 +1887,7 @@ impl fmt::Debug for NaiveDate {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let year = self.year();
         let mdf = self.mdf();
-        if 0 <= year && year <= 9999 {
+        if (0..=9999).contains(&year) {
             write!(f, "{:04}-{:02}-{:02}", year, mdf.month(), mdf.day())
         } else {
             // ISO 8601 requires the explicit sign for out-of-range years

src/naive/internals.rs

@@ -297,7 +297,7 @@ impl Of {
     pub(super) fn valid(&self) -> bool {
         let Of(of) = *self;
         let ol = of >> 3;
-        MIN_OL <= ol && ol <= MAX_OL
+        (MIN_OL..=MAX_OL).contains(&ol)
     }
 
     #[inline]

src/naive/isoweek.rs

@@ -135,7 +135,7 @@ impl fmt::Debug for IsoWeek {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let year = self.year();
         let week = self.week();
-        if 0 <= year && year <= 9999 {
+        if (0..=9999).contains(&year) {
             write!(f, "{:04}-W{:02}", year, week)
         } else {
             // ISO 8601 requires the explicit sign for out-of-range years

src/naive/time/mod.rs

@@ -586,7 +586,7 @@ impl NaiveTime {
             secs += 1;
         }
         debug_assert!(-86_400 <= secs && secs < 2 * 86_400);
-        debug_assert!(0 <= frac && frac < 1_000_000_000);
+        debug_assert!((0..1_000_000_000).contains(&frac));
 
         if secs < 0 {
             secs += 86_400;
@@ -595,7 +595,7 @@ impl NaiveTime {
             secs -= 86_400;
             morerhssecs += 86_400;
         }
-        debug_assert!(0 <= secs && secs < 86_400);
+        debug_assert!((0..86_400).contains(&secs));
 
         (NaiveTime { secs: secs as u32, frac: frac as u32 }, morerhssecs)
     }

src/offset/local/tz_info/rule.rs

@@ -365,13 +365,13 @@ fn parse_name<'a>(cursor: &mut Cursor<'a>) -> Result<&'a [u8], Error> {
 fn parse_offset(cursor: &mut Cursor) -> Result<i32, Error> {
     let (sign, hour, minute, second) = parse_signed_hhmmss(cursor)?;
 
-    if hour < 0 || hour > 24 {
+    if !(0..=24).contains(&hour) {
         return Err(Error::InvalidTzString("invalid offset hour"));
     }
-    if minute < 0 || minute > 59 {
+    if !(0..=59).contains(&minute) {
         return Err(Error::InvalidTzString("invalid offset minute"));
     }
-    if second < 0 || second > 59 {
+    if !(0..=59).contains(&second) {
         return Err(Error::InvalidTzString("invalid offset second"));
     }
 
@@ -382,13 +382,13 @@ fn parse_offset(cursor: &mut Cursor) -> Result<i32, Error> {
 fn parse_rule_time(cursor: &mut Cursor) -> Result<i32, Error> {
     let (hour, minute, second) = parse_hhmmss(cursor)?;
 
-    if hour < 0 || hour > 24 {
+    if !(0..=24).contains(&hour) {
         return Err(Error::InvalidTzString("invalid day time hour"));
     }
-    if minute < 0 || minute > 59 {
+    if !(0..=59).contains(&minute) {
         return Err(Error::InvalidTzString("invalid day time minute"));
     }
-    if second < 0 || second > 59 {
+    if !(0..=59).contains(&second) {
         return Err(Error::InvalidTzString("invalid day time second"));
     }
 
@@ -402,10 +402,10 @@ fn parse_rule_time_extended(cursor: &mut Cursor) -> Result<i32, Error> {
     if hour < -167 || hour > 167 {
         return Err(Error::InvalidTzString("invalid day time hour"));
     }
-    if minute < 0 || minute > 59 {
+    if !(0..=59).contains(&minute) {
         return Err(Error::InvalidTzString("invalid day time minute"));
     }
-    if second < 0 || second > 59 {
+    if !(0..=59).contains(&second) {
         return Err(Error::InvalidTzString("invalid day time second"));
     }
 
@@ -496,7 +496,7 @@ impl RuleDay {
 
     /// Construct a transition rule day represented by a Julian day in `[1, 365]`, without taking occasional Feb 29 into account, which is not referenceable
     fn julian_1(julian_day_1: u16) -> Result<Self, Error> {
-        if julian_day_1 < 1 || julian_day_1 > 365 {
+        if !(1..=365).contains(&julian_day_1) {
             return Err(Error::TransitionRule("invalid rule day julian day"));
         }
 
@@ -514,11 +514,11 @@ impl RuleDay {
 
     /// Construct a transition rule day represented by a month, a month week and a week day
     fn month_weekday(month: u8, week: u8, week_day: u8) -> Result<Self, Error> {
-        if month < 1 || month > 12 {
+        if !(1..=12).contains(&month) {
             return Err(Error::TransitionRule("invalid rule day month"));
         }
 
-        if week < 1 || week > 5 {
+        if !(1..=5).contains(&week) {
             return Err(Error::TransitionRule("invalid rule day week"));
         }
 

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],
@@ -482,7 +482,7 @@ impl TimeZoneName {
     fn new(input: &[u8]) -> Result<Self, Error> {
         let len = input.len();
 
-        if len < 3 || len > 7 {
+        if !(3..=7).contains(&len) {
             return Err(Error::LocalTimeType(
                 "time zone name must have between 3 and 7 characters",
             ));
@@ -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(),
         }
     }