default to UTC when /etc/localtime is missing

chronotope · Aug 5, 2022 · 28562f0 · 28562f0
1 parent 0b7feac
commit 28562f0
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Showing 2 changed files with 25 additions and 16 deletions.
diff --git a/src/offset/local/tz_info/timezone.rs b/src/offset/local/tz_info/timezone.rs
@@ -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],
@@ -817,14 +817,16 @@ mod tests {
                 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);
+                // To be discussed - does this make sense in the context
+                // of Issue https://github.com/chronotope/chrono/issues/755
+                // 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")?;

diff --git a/src/offset/local/unix.rs b/src/offset/local/unix.rs
@@ -47,12 +47,18 @@ 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
+                    Source::LocalTime { mtime: SystemTime::now(), last_checked: SystemTime::now() }
+                }
             },
         }
     }
@@ -91,8 +97,9 @@ struct Cache {
 
 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().unwrap_or_else(|_| TimeZone::utc()),
             source: Source::default(),
         }
     }