Fix creating a DateTime with NaiveDateTime::{MIN, MAX}

chronotope · May 19, 2023 · 7a3747c · 7a3747c
1 parent 4ac7509
commit 7a3747c
Showing 1 changed file with 47 additions and 2 deletions.
diff --git a/src/offset/mod.rs b/src/offset/mod.rs
@@ -473,8 +473,8 @@ pub trait TimeZone: Sized + Clone {
     /// Converts the local `NaiveDateTime` to the timezone-aware `DateTime` if possible.
     #[allow(clippy::wrong_self_convention)]
     fn from_local_datetime(&self, local: &NaiveDateTime) -> LocalResult<DateTime<Self>> {
-        self.offset_from_local_datetime(local)
-            .map(|offset| DateTime::from_utc(*local - offset.fix(), offset))
+        let local_result_offset = self.offset_from_local_datetime(local);
+        local_time_min_offset(local_result_offset, local).unwrap_or(LocalResult::None)
     }
 
     /// Creates the offset for given UTC `NaiveDate`. This cannot fail.
@@ -500,10 +500,55 @@ pub trait TimeZone: Sized + Clone {
     }
 }
 
+/// Helper function to map `LocalResult<FixedOffset>` to `LocalResult<DateTime<Local>>`.
+/// Returns `None` on out-of-range.
+fn local_time_min_offset<Tz: TimeZone>(
+    local_result: LocalResult<Tz::Offset>,
+    local_time: &NaiveDateTime,
+) -> Option<LocalResult<DateTime<Tz>>> {
+    Some(match local_result {
+        LocalResult::None => LocalResult::None,
+        LocalResult::Single(offset) => LocalResult::Single(DateTime::from_utc(
+            local_time.checked_sub_offset(offset.fix())?,
+            offset,
+        )),
+        LocalResult::Ambiguous(o1, o2) => LocalResult::Ambiguous(
+            DateTime::from_utc(local_time.checked_sub_offset(o1.fix())?, o1),
+            DateTime::from_utc(local_time.checked_sub_offset(o2.fix())?, o2),
+        ),
+    })
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
+    #[test]
+    fn test_fixed_offset_min_max_dates() {
+        for offset_hour in -23..=23 {
+            dbg!(offset_hour);
+            let offset = FixedOffset::east_opt(offset_hour * 60 * 60).unwrap();
+
+            let local_max = offset.from_utc_datetime(&NaiveDateTime::MAX);
+            assert_eq!(local_max.naive_utc(), NaiveDateTime::MAX);
+            let local_min = offset.from_utc_datetime(&NaiveDateTime::MIN);
+            assert_eq!(local_min.naive_utc(), NaiveDateTime::MIN);
+
+            let local_max = offset.from_local_datetime(&NaiveDateTime::MAX);
+            if offset_hour >= 0 {
+                assert_eq!(local_max.unwrap().naive_local(), NaiveDateTime::MAX);
+            } else {
+                assert_eq!(local_max, LocalResult::None);
+            }
+            let local_min = offset.from_local_datetime(&NaiveDateTime::MIN);
+            if offset_hour <= 0 {
+                assert_eq!(local_min.unwrap().naive_local(), NaiveDateTime::MIN);
+            } else {
+                assert_eq!(local_min, LocalResult::None);
+            }
+        }
+    }
+
     #[test]
     fn test_negative_millis() {
         let dt = Utc.timestamp_millis_opt(-1000).unwrap();