From 78b8601934dbaa132dce5e9dfc459129c22ce286 Mon Sep 17 00:00:00 2001
From: Rob <124158982+rob-sil@users.noreply.github.com>
Date: Fri, 16 Feb 2024 04:54:49 -0800
Subject: [PATCH] Handle rounding to the nearest zero

---
 crates/polars-time/src/round.rs                  |  4 ++++
 crates/polars-time/src/truncate.rs               | 12 ++++++++----
 py-polars/tests/unit/namespaces/test_datetime.py | 16 ++++++++++++++++
 3 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/crates/polars-time/src/round.rs b/crates/polars-time/src/round.rs
index c7f512d510964..0fd166fbad717 100644
--- a/crates/polars-time/src/round.rs
+++ b/crates/polars-time/src/round.rs
@@ -53,6 +53,10 @@ impl PolarsRound for DurationChunked {
             TimeUnit::Milliseconds => (every.duration_ms(), offset.duration_ms()),
         };
 
+        if every == 0 {
+            polars_bail!(InvalidOperation: "duration cannot be zero.")
+        }
+
         let out = self.apply_values(|duration| {
             // Round half-way values away from zero
             let half_away = duration.signum() * every / 2;
diff --git a/crates/polars-time/src/truncate.rs b/crates/polars-time/src/truncate.rs
index c7487cb72cd70..809cbe9d6a5a2 100644
--- a/crates/polars-time/src/truncate.rs
+++ b/crates/polars-time/src/truncate.rs
@@ -113,13 +113,17 @@ impl PolarsTruncate for DurationChunked {
                 if every_duration.is_constant_duration() {
                     let every_units = to_time_unit(&every_duration);
 
+                    if every_units == 0 {
+                        polars_bail!(InvalidOperation: "duration cannot be zero.")
+                    }
+
                     Ok(self
                         .0
                         .apply_values(|duration| duration - duration % every_units + offset_units))
                 } else {
-                    Err(polars_err!(InvalidOperation:
+                    polars_bail!(InvalidOperation:
                         "Cannot truncate a Duration series to a non-constant duration."
-                    ))
+                    )
                 }
             } else {
                 Ok(Int64Chunked::full_null(self.name(), self.len()))
@@ -133,9 +137,9 @@ impl PolarsTruncate for DurationChunked {
 
                         Ok(Some(duration - duration % every_units + offset_units))
                     } else {
-                        Err(polars_err!(InvalidOperation:
+                        polars_bail!(InvalidOperation:
                             "Cannot truncate a Duration series to a non-constant duration."
-                        ))
+                        )
                     }
                 } else {
                     Ok(None)
diff --git a/py-polars/tests/unit/namespaces/test_datetime.py b/py-polars/tests/unit/namespaces/test_datetime.py
index e36340bada2b4..5f2483d690b42 100644
--- a/py-polars/tests/unit/namespaces/test_datetime.py
+++ b/py-polars/tests/unit/namespaces/test_datetime.py
@@ -538,6 +538,14 @@ def test_truncate_duration(time_unit: TimeUnit) -> None:
     assert_series_equal(durations.dt.truncate("10s"), expected)
 
 
+def test_truncate_duration_zero() -> None:
+    """Truncating to the nearest zero should raise a descriptive error."""
+    durations = pl.Series([timedelta(seconds=21), timedelta(seconds=35)])
+
+    with pytest.raises(InvalidOperationError, match="duration cannot be zero"):
+        durations.dt.truncate("0s")
+
+
 @pytest.mark.parametrize("every_unit", ["d", "w", "mo", "q", "y"])
 def test_truncated_duration_non_constant(every_unit: str) -> None:
     # Duration series can't be truncated to non-constant durations
@@ -614,6 +622,14 @@ def test_round_duration(time_unit: TimeUnit) -> None:
     assert_series_equal(durations.dt.round("10s"), expected)
 
 
+def test_round_duration_zero() -> None:
+    """Rounding to the nearest zero should raise a descriptive error."""
+    durations = pl.Series([timedelta(seconds=21), timedelta(seconds=35)])
+
+    with pytest.raises(InvalidOperationError, match="duration cannot be zero"):
+        durations.dt.round("0s")
+
+
 @pytest.mark.parametrize("every", ["d", "w", "mo", "q", "y"])
 def test_round_duration_non_constant(every: str) -> None:
     # Duration series can't be rounded to non-constant durations