Improve TZ environment variable handling and use TZDIR

src/output/table.rs

@@ -4,7 +4,7 @@ use std::ops::Deref;
 use std::sync::{Mutex, MutexGuard};
 
 use datetime::TimeZone;
-use zoneinfo_compiled::{CompiledData, Result as TZResult};
+use zoneinfo_compiled::CompiledData;
 
 use lazy_static::lazy_static;
 use log::*;
@@ -282,13 +282,12 @@ impl Environment {
 
  fn load_all() -> Self {
  let tz = match determine_time_zone() {
- Ok(t) => {
- Some(t)
- }
- Err(ref e) => {
- println!("Unable to determine time zone: {}", e);
+ UserTimeZone::Tz(tz) => Some(tz),
+ UserTimeZone::Utc => None,
+ UserTimeZone::Error => {
+ debug!("Unable to determine time zone, use UTC instead.");
  None
- }
+ },
  };
 
  let numeric = locale::Numeric::load_user_locale()
@@ -300,23 +299,56 @@ impl Environment {
  }
 }
 
-fn determine_time_zone() -> TZResult<TimeZone> {
- if let Ok(file) = env::var("TZ") {
- TimeZone::from_file({
- if file.starts_with("/") {
- file
- } else {
- format!("/usr/share/zoneinfo/{}", {
- if file.starts_with(":") {
- file.replacen(":", "", 1)
- } else {
- file
- }
- })
- }
- })
- } else {
- TimeZone::from_file("/etc/localtime")
+enum UserTimeZone {
+ Tz(TimeZone),
+ Utc,
+ Error,
+}
+
+/// Documentation of `TZ` and `TZDIR` is barely existent.
+/// This function rely on how glibc and musl work.
+/// - glibc: [tzset.c](https://github.com/bminor/glibc/blob/24f261f27fb8fd19ae294ff2a13bc5b7a0bafc91/time/tzset.c#L365) and [tzfile.c](https://github.com/bminor/glibc/blob/24f261f27fb8fd19ae294ff2a13bc5b7a0bafc91/time/tzfile.c#L100)
+/// - [musl](https://github.com/ifduyue/musl/blob/aad50fcd791e009961621ddfbe3d4c245fd689a3/src/time/__tz.c#L125)
+fn determine_time_zone() -> UserTimeZone {
+ let tz_env = match env::var("TZ") {
+ Err(_) => return read_timezone_file("/etc/localtime"),
+ Ok(tz_env) if tz_env.is_empty() => return UserTimeZone::Utc,
+ Ok(tz_env) => tz_env,
+ };
+
+ let tz_env = tz_env.strip_prefix(':').map(ToString::to_string).unwrap_or(tz_env);
+
+ if tz_env.starts_with('/') {
+ return read_timezone_file(&tz_env);
+ }
+
+ // For relative paths, use TZDIR like glibc; it’s used by at least NixOS.
+ if let Ok(tz_dir) = env::var("TZDIR") {
+ return read_timezone_file(&format!("{}/{}", tz_dir, tz_env));
+ }
+
+ // If TZDIR isn’t defined, try the other directories that musl is checking
+ let tz_dirs = [
+ "/usr/share/zoneinfo".to_string(),
+ "/share/zoneinfo".to_string(),
+ "/etc/zoneinfo".to_string(),
+ ];
+ for tz_dir in &tz_dirs {
+ if let UserTimeZone::Tz(tz) = read_timezone_file(&format!("{}/{}", tz_dir, tz_env)) {
+ return UserTimeZone::Tz(tz);
+ }
+ }
+
+ UserTimeZone::Error
+}
+
+fn read_timezone_file(path: &str) -> UserTimeZone {
+ match TimeZone::from_file(path) {
+ Ok(tz) => UserTimeZone::Tz(tz),
+ Err(e) => {
+ debug!("Trying zoneinfo file {}: {}", path, e);
+ UserTimeZone::Error
+ },
  }
 }