fix: Properly calculate duration units (#18869)

Author: coastalwhite

crates/polars-ops/src/series/ops/duration.rs

@@ -72,19 +72,24 @@ pub fn impl_duration(s: &[Column], time_unit: TimeUnit) -> PolarsResult<Column>
         TimeUnit::Milliseconds => MILLISECONDS,
     };
     if !is_zero_scalar(&seconds) {
-        duration = ((duration + seconds)? * multiplier)?;
+        let units = seconds * multiplier;
+        duration = (duration + units?)?;
     }
     if !is_zero_scalar(&minutes) {
-        duration = ((duration + minutes)? * (multiplier * 60))?;
+        let units = minutes * (multiplier * 60);
+        duration = (duration + units?)?;
     }
     if !is_zero_scalar(&hours) {
-        duration = ((duration + hours)? * (multiplier * 60 * 60))?;
+        let units = hours * (multiplier * 60 * 60);
+        duration = (duration + units?)?;
     }
     if !is_zero_scalar(&days) {
-        duration = ((duration + days)? * (multiplier * SECONDS_IN_DAY))?;
+        let units = days * (multiplier * SECONDS_IN_DAY);
+        duration = (duration + units?)?;
     }
     if !is_zero_scalar(&weeks) {
-        duration = ((duration + weeks)? * (multiplier * SECONDS_IN_DAY * 7))?;
+        let units = weeks * (multiplier * SECONDS_IN_DAY * 7);
+        duration = (duration + units?)?;
     }
 
     duration

py-polars/tests/unit/datatypes/test_duration.py

@@ -60,3 +60,36 @@ def test_series_duration_var_overflow() -> None:
     s = pl.Series([timedelta(days=10), timedelta(days=20), timedelta(days=40)])
     with pytest.raises(PanicException, match="OverflowError"):
         s.var()
+
+
+def test_series_duration_units() -> None:
+    td = timedelta
+
+    assert_frame_equal(
+        pl.DataFrame({"x": [0, 1, 2, 3]}).select(x=pl.duration(weeks=pl.col("x"))),
+        pl.DataFrame({"x": [td(weeks=i) for i in range(4)]}),
+    )
+    assert_frame_equal(
+        pl.DataFrame({"x": [0, 1, 2, 3]}).select(x=pl.duration(days=pl.col("x"))),
+        pl.DataFrame({"x": [td(days=i) for i in range(4)]}),
+    )
+    assert_frame_equal(
+        pl.DataFrame({"x": [0, 1, 2, 3]}).select(x=pl.duration(hours=pl.col("x"))),
+        pl.DataFrame({"x": [td(hours=i) for i in range(4)]}),
+    )
+    assert_frame_equal(
+        pl.DataFrame({"x": [0, 1, 2, 3]}).select(x=pl.duration(minutes=pl.col("x"))),
+        pl.DataFrame({"x": [td(minutes=i) for i in range(4)]}),
+    )
+    assert_frame_equal(
+        pl.DataFrame({"x": [0, 1, 2, 3]}).select(
+            x=pl.duration(milliseconds=pl.col("x"))
+        ),
+        pl.DataFrame({"x": [td(milliseconds=i) for i in range(4)]}),
+    )
+    assert_frame_equal(
+        pl.DataFrame({"x": [0, 1, 2, 3]}).select(
+            x=pl.duration(microseconds=pl.col("x"))
+        ),
+        pl.DataFrame({"x": [td(microseconds=i) for i in range(4)]}),
+    )