Fix panic in NaiveDateTime::and_local_timezone

chronotope · Aug 6, 2023 · cdc9884 · cdc9884
1 parent 90c8384
commit cdc9884
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Showing 2 changed files with 44 additions and 4 deletions.
diff --git a/src/naive/datetime/mod.rs b/src/naive/datetime/mod.rs
@@ -17,7 +17,7 @@ use crate::format::DelayedFormat;
 use crate::format::{parse, parse_and_remainder, ParseError, ParseResult, Parsed, StrftimeItems};
 use crate::format::{Fixed, Item, Numeric, Pad};
 use crate::naive::{Days, IsoWeek, NaiveDate, NaiveTime};
-use crate::offset::Utc;
+use crate::offset::{Offset, Utc};
 use crate::oldtime::Duration as OldDuration;
 use crate::{DateTime, Datelike, FixedOffset, LocalResult, Months, TimeZone, Timelike, Weekday};
 #[cfg(feature = "rustc-serialize")]
@@ -948,7 +948,8 @@ impl NaiveDateTime {
     /// ```
     #[must_use]
     pub fn and_local_timezone<Tz: TimeZone>(&self, tz: Tz) -> LocalResult<DateTime<Tz>> {
-        tz.from_local_datetime(self)
+        let local_result_offset = tz.offset_from_local_datetime(self);
+        local_time_min_offset(local_result_offset, self).unwrap_or(LocalResult::None)
     }
 
     /// Converts the `NaiveDateTime` into the timezone-aware `DateTime<Utc>`.
@@ -971,6 +972,25 @@ impl NaiveDateTime {
     pub const MAX: Self = Self { date: NaiveDate::MAX, time: NaiveTime::MAX };
 }
 
+/// 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_naive_utc_and_offset(
+            local_time.checked_sub_offset(offset.fix())?,
+            offset,
+        )),
+        LocalResult::Ambiguous(o1, o2) => LocalResult::Ambiguous(
+            DateTime::from_naive_utc_and_offset(local_time.checked_sub_offset(o1.fix())?, o1),
+            DateTime::from_naive_utc_and_offset(local_time.checked_sub_offset(o2.fix())?, o2),
+        ),
+    })
+}
+
 impl Datelike for NaiveDateTime {
     /// Returns the year number in the [calendar date](./struct.NaiveDate.html#calendar-date).
     ///

diff --git a/src/naive/datetime/tests.rs b/src/naive/datetime/tests.rs
@@ -1,7 +1,6 @@
 use super::NaiveDateTime;
 use crate::oldtime::Duration;
-use crate::NaiveDate;
-use crate::{Datelike, FixedOffset, Utc};
+use crate::{Datelike, FixedOffset, LocalResult, NaiveDate, Utc};
 
 #[test]
 fn test_datetime_from_timestamp_millis() {
@@ -431,3 +430,24 @@ fn test_checked_sub_offset() {
     // out of range
     assert!(NaiveDateTime::MAX.checked_sub_offset(negative_offset).is_none());
 }
+
+#[test]
+fn test_and_timezone_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 = NaiveDateTime::MAX.and_local_timezone(offset);
+        if offset_hour >= 0 {
+            assert_eq!(local_max.unwrap().naive_local(), NaiveDateTime::MAX);
+        } else {
+            assert_eq!(local_max, LocalResult::None);
+        }
+        let local_min = NaiveDateTime::MIN.and_local_timezone(offset);
+        if offset_hour <= 0 {
+            assert_eq!(local_min.unwrap().naive_local(), NaiveDateTime::MIN);
+        } else {
+            assert_eq!(local_min, LocalResult::None);
+        }
+    }
+}