Fix issue chronotope#658 duration_round by zero panics (chronotope#659)

CHANGELOG.md

@@ -21,6 +21,7 @@ Versions with only mechanical changes will be omitted from the following list.
 * Add `DateTime::from_local()` to construct from given local date and time (#572)
 * Correct build for wasm32-unknown-emscripten target (#568)
 * Change `Local::now()` and `Utc::now()` documentation from "current date" to "current date and time" (#647)
+* Fix `duration_round` panic on rounding by `Duration::zero()` (#658)
 
 ## 0.4.19
 

src/round.rs

@@ -185,6 +185,9 @@ where
         if span > stamp.abs() {
             return Err(RoundingError::DurationExceedsTimestamp);
         }
+        if span == 0 {
+            return Ok(original);
+        }
         let delta_down = stamp % span;
         if delta_down == 0 {
             Ok(original)
@@ -394,6 +397,11 @@ mod tests {
     fn test_duration_round() {
         let dt = Utc.ymd(2016, 12, 31).and_hms_nano(23, 59, 59, 175_500_000);
 
+        assert_eq!(
+            dt.duration_round(Duration::zero()).unwrap().to_string(),
+            "2016-12-31 23:59:59.175500 UTC"
+        );
+
         assert_eq!(
             dt.duration_round(Duration::milliseconds(10)).unwrap().to_string(),
             "2016-12-31 23:59:59.180 UTC"
@@ -456,6 +464,11 @@ mod tests {
     fn test_duration_round_naive() {
         let dt = Utc.ymd(2016, 12, 31).and_hms_nano(23, 59, 59, 175_500_000).naive_utc();
 
+        assert_eq!(
+            dt.duration_round(Duration::zero()).unwrap().to_string(),
+            "2016-12-31 23:59:59.175500"
+        );
+
         assert_eq!(
             dt.duration_round(Duration::milliseconds(10)).unwrap().to_string(),
             "2016-12-31 23:59:59.180"