feat!: Restrict casting for temporal data types

crates/polars-core/src/chunked_array/logical/date.rs

@@ -30,6 +30,7 @@ impl LogicalType for DateChunked {
     fn cast(&self, dtype: &DataType) -> PolarsResult<Series> {
         use DataType::*;
         match dtype {
+            Date => Ok(self.clone().into_series()),
             #[cfg(feature = "dtype-datetime")]
             Datetime(tu, tz) => {
                 let casted = self.0.cast(dtype)?;
@@ -43,11 +44,14 @@ impl LogicalType for DateChunked {
                     .into_datetime(*tu, tz.clone())
                     .into_series())
             },
-            #[cfg(feature = "dtype-time")]
-            Time => {
-                polars_bail!(ComputeError: "cannot cast `Date` to `Time`");
+            dt if dt.is_numeric() => self.0.cast(dtype),
+            dt => {
+                polars_bail!(
+                    InvalidOperation:
+                    "casting from {:?} to {:?} not supported",
+                    self.dtype(), dt
+                )
             },
-            _ => self.0.cast(dtype),
         }
     }
 }

crates/polars-core/src/chunked_array/logical/datetime.rs

@@ -30,17 +30,19 @@ impl LogicalType for DatetimeChunked {
 
     fn cast(&self, dtype: &DataType) -> PolarsResult<Series> {
         use DataType::*;
-        match (self.dtype(), dtype) {
-            (Datetime(from_unit, _), Datetime(to_unit, tz)) => {
+        use TimeUnit::*;
+        let out = match dtype {
+            Datetime(to_unit, tz) => {
+                let from_unit = self.time_unit();
                 let (multiplier, divisor) = match (from_unit, to_unit) {
                     // scaling from lower precision to higher precision
-                    (TimeUnit::Milliseconds, TimeUnit::Nanoseconds) => (Some(1_000_000i64), None),
-                    (TimeUnit::Milliseconds, TimeUnit::Microseconds) => (Some(1_000i64), None),
-                    (TimeUnit::Microseconds, TimeUnit::Nanoseconds) => (Some(1_000i64), None),
+                    (Milliseconds, Nanoseconds) => (Some(1_000_000i64), None),
+                    (Milliseconds, Microseconds) => (Some(1_000i64), None),
+                    (Microseconds, Nanoseconds) => (Some(1_000i64), None),
                     // scaling from higher precision to lower precision
-                    (TimeUnit::Nanoseconds, TimeUnit::Milliseconds) => (None, Some(1_000_000i64)),
-                    (TimeUnit::Nanoseconds, TimeUnit::Microseconds) => (None, Some(1_000i64)),
-                    (TimeUnit::Microseconds, TimeUnit::Milliseconds) => (None, Some(1_000i64)),
+                    (Nanoseconds, Milliseconds) => (None, Some(1_000_000i64)),
+                    (Nanoseconds, Microseconds) => (None, Some(1_000i64)),
+                    (Microseconds, Milliseconds) => (None, Some(1_000i64)),
                     _ => return self.0.cast(dtype),
                 };
                 let result = match multiplier {
@@ -61,7 +63,7 @@ impl LogicalType for DatetimeChunked {
                 result
             },
             #[cfg(feature = "dtype-date")]
-            (Datetime(tu, _), Date) => {
+            Date => {
                 let cast_to_date = |tu_in_day: i64| {
                     let mut dt = self
                         .0
@@ -73,18 +75,18 @@ impl LogicalType for DatetimeChunked {
                     dt.set_sorted_flag(self.is_sorted_flag());
                     Ok(dt)
                 };
-                match tu {
-                    TimeUnit::Nanoseconds => cast_to_date(NS_IN_DAY),
-                    TimeUnit::Microseconds => cast_to_date(US_IN_DAY),
-                    TimeUnit::Milliseconds => cast_to_date(MS_IN_DAY),
+                match self.time_unit() {
+                    Nanoseconds => cast_to_date(NS_IN_DAY),
+                    Microseconds => cast_to_date(US_IN_DAY),
+                    Milliseconds => cast_to_date(MS_IN_DAY),
                 }
             },
             #[cfg(feature = "dtype-time")]
-            (Datetime(tu, _), Time) => {
-                let (scaled_mod, multiplier) = match tu {
-                    TimeUnit::Nanoseconds => (NS_IN_DAY, 1i64),
-                    TimeUnit::Microseconds => (US_IN_DAY, 1_000i64),
-                    TimeUnit::Milliseconds => (MS_IN_DAY, 1_000_000i64),
+            Time => {
+                let (scaled_mod, multiplier) = match self.time_unit() {
+                    Nanoseconds => (NS_IN_DAY, 1i64),
+                    Microseconds => (US_IN_DAY, 1_000i64),
+                    Milliseconds => (MS_IN_DAY, 1_000_000i64),
                 };
                 return Ok(self
                     .0
@@ -95,9 +97,16 @@ impl LogicalType for DatetimeChunked {
                     .into_time()
                     .into_series());
             },
-            _ => return self.0.cast(dtype),
-        }
-        .map(|mut s| {
+            dt if dt.is_numeric() => return self.0.cast(dtype),
+            dt => {
+                polars_bail!(
+                    InvalidOperation:
+                    "casting from {:?} to {:?} not supported",
+                    self.dtype(), dt
+                )
+            },
+        };
+        out.map(|mut s| {
             // TODO!; implement the divisions/multipliers above
             // in a checked manner so that we raise on overflow
             s.set_sorted_flag(self.is_sorted_flag());

crates/polars-core/src/chunked_array/logical/duration.rs

@@ -29,38 +29,35 @@ impl LogicalType for DurationChunked {
 
     fn cast(&self, dtype: &DataType) -> PolarsResult<Series> {
         use DataType::*;
-        match (self.dtype(), dtype) {
-            (Duration(TimeUnit::Milliseconds), Duration(TimeUnit::Nanoseconds)) => {
-                Ok((self.0.as_ref() * 1_000_000i64)
-                    .into_duration(TimeUnit::Nanoseconds)
-                    .into_series())
+        use TimeUnit::*;
+        match dtype {
+            Duration(tu) => {
+                let to_unit = *tu;
+                let out = match (self.time_unit(), to_unit) {
+                    (Milliseconds, Microseconds) => self.0.as_ref() * 1_000i64,
+                    (Milliseconds, Nanoseconds) => self.0.as_ref() * 1_000_000i64,
+                    (Microseconds, Milliseconds) => {
+                        self.0.as_ref().wrapping_trunc_div_scalar(1_000i64)
+                    },
+                    (Microseconds, Nanoseconds) => self.0.as_ref() * 1_000i64,
+                    (Nanoseconds, Milliseconds) => {
+                        self.0.as_ref().wrapping_trunc_div_scalar(1_000_000i64)
+                    },
+                    (Nanoseconds, Microseconds) => {
+                        self.0.as_ref().wrapping_trunc_div_scalar(1_000i64)
+                    },
+                    _ => return Ok(self.clone().into_series()),
+                };
+                Ok(out.into_duration(to_unit).into_series())
             },
-            (Duration(TimeUnit::Milliseconds), Duration(TimeUnit::Microseconds)) => {
-                Ok((self.0.as_ref() * 1_000i64)
-                    .into_duration(TimeUnit::Microseconds)
-                    .into_series())
+            dt if dt.is_numeric() => self.0.cast(dtype),
+            dt => {
+                polars_bail!(
+                    InvalidOperation:
+                    "casting from {:?} to {:?} not supported",
+                    self.dtype(), dt
+                )
             },
-            (Duration(TimeUnit::Microseconds), Duration(TimeUnit::Milliseconds)) => {
-                Ok((self.0.as_ref().wrapping_trunc_div_scalar(1_000i64))
-                    .into_duration(TimeUnit::Milliseconds)
-                    .into_series())
-            },
-            (Duration(TimeUnit::Microseconds), Duration(TimeUnit::Nanoseconds)) => {
-                Ok((self.0.as_ref() * 1_000i64)
-                    .into_duration(TimeUnit::Nanoseconds)
-                    .into_series())
-            },
-            (Duration(TimeUnit::Nanoseconds), Duration(TimeUnit::Milliseconds)) => {
-                Ok((self.0.as_ref().wrapping_trunc_div_scalar(1_000_000i64))
-                    .into_duration(TimeUnit::Milliseconds)
-                    .into_series())
-            },
-            (Duration(TimeUnit::Nanoseconds), Duration(TimeUnit::Microseconds)) => {
-                Ok((self.0.as_ref().wrapping_trunc_div_scalar(1_000i64))
-                    .into_duration(TimeUnit::Microseconds)
-                    .into_series())
-            },
-            _ => self.0.cast(dtype),
         }
     }
 }

crates/polars-core/src/chunked_array/logical/time.rs

@@ -31,6 +31,8 @@ impl LogicalType for TimeChunked {
     fn cast(&self, dtype: &DataType) -> PolarsResult<Series> {
         use DataType::*;
         match dtype {
+            Time => Ok(self.clone().into_series()),
+            #[cfg(feature = "dtype-duration")]
             Duration(tu) => {
                 let out = self.0.cast(&DataType::Duration(TimeUnit::Nanoseconds));
                 if !matches!(tu, TimeUnit::Nanoseconds) {
@@ -39,15 +41,22 @@ impl LogicalType for TimeChunked {
                     out
                 }
             },
-            #[cfg(feature = "dtype-date")]
-            Date => {
-                polars_bail!(ComputeError: "cannot cast `Time` to `Date`");
-            },
             #[cfg(feature = "dtype-datetime")]
             Datetime(_, _) => {
-                polars_bail!(ComputeError: "cannot cast `Time` to `Datetime`; consider using `dt.combine`");
+                polars_bail!(
+                    InvalidOperation:
+                    "casting from {:?} to {:?} not supported; consider using `dt.combine`",
+                    self.dtype(), dtype
+                )
+            },
+            dt if dt.is_numeric() => self.0.cast(dtype),
+            _ => {
+                polars_bail!(
+                    InvalidOperation:
+                    "casting from {:?} to {:?} not supported",
+                    self.dtype(), dtype
+                )
             },
-            _ => self.0.cast(dtype),
         }
     }
 }

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

@@ -239,17 +239,22 @@ def test_int_to_python_datetime() -> None:
             datetime(1970, 1, 1, 0, 0, 0, 200000),
         ),
     ]
+
+    assert df.select(pl.col(col).dt.timestamp() for col in ("c", "d", "e")).rows() == [
+        (100000000000, 100000000, 100000),
+        (200000000000, 200000000, 200000),
+    ]
+
     assert df.select(
-        [pl.col(col).dt.timestamp() for col in ("c", "d", "e")]
-        + [
-            getattr(pl.col("b").cast(pl.Duration).dt, f"total_{unit}")().alias(
+        [
+            getattr(pl.col("a").cast(pl.Duration).dt, f"total_{unit}")().alias(
                 f"u[{unit}]"
             )
             for unit in ("milliseconds", "microseconds", "nanoseconds")
         ]
     ).rows() == [
-        (100000000000, 100000000, 100000, 100000, 100000000, 100000000000),
-        (200000000000, 200000000, 200000, 200000, 200000000, 200000000000),
+        (100000, 100000000, 100000000000),
+        (200000, 200000000, 200000000000),
     ]
 
 

py-polars/tests/unit/operations/test_cast.py

@@ -607,15 +607,15 @@ def test_cast_categorical_name_retention(
 
 def test_cast_date_to_time() -> None:
     s = pl.Series([date(1970, 1, 1), date(2000, 12, 31)])
-    msg = "cannot cast `Date` to `Time`"
-    with pytest.raises(pl.ComputeError, match=msg):
+    msg = "casting from Date to Time not supported"
+    with pytest.raises(pl.InvalidOperationError, match=msg):
         s.cast(pl.Time)
 
 
 def test_cast_time_to_date() -> None:
     s = pl.Series([time(0, 0), time(20, 00)])
-    msg = "cannot cast `Time` to `Date`"
-    with pytest.raises(pl.ComputeError, match=msg):
+    msg = "casting from Time to Date not supported"
+    with pytest.raises(pl.InvalidOperationError, match=msg):
         s.cast(pl.Date)
 
 
@@ -648,3 +648,27 @@ def test_cast_decimal_to_decimal_high_precision() -> None:
 
     assert result.dtype == target_dtype
     assert result.to_list() == values
+
+
+def test_err_on_time_datetime_cast() -> None:
+    s = pl.Series([time(10, 0, 0), time(11, 30, 59)])
+    with pytest.raises(
+        pl.InvalidOperationError,
+        match="casting from Time to Datetime\\(Microseconds, None\\) not supported; consider using `dt.combine`",
+    ):
+        s.cast(pl.Datetime)
+
+
+def test_err_on_invalid_time_zone_cast() -> None:
+    s = pl.Series([datetime(2021, 1, 1)])
+    with pytest.raises(pl.ComputeError, match=r"unable to parse time zone: 'qwerty'"):
+        s.cast(pl.Datetime("us", "qwerty"))
+
+
+def test_invalid_inner_type_cast_list() -> None:
+    s = pl.Series([[-1, 1]])
+    with pytest.raises(
+        pl.InvalidOperationError,
+        match=r"cannot cast List inner type: 'Int64' to Categorical",
+    ):
+        s.cast(pl.List(pl.Categorical))

py-polars/tests/unit/test_errors.py

@@ -497,27 +497,6 @@ def test_cast_err_column_value_highlighting(
         test_df.with_columns(pl.all().cast(type))
 
 
-def test_err_on_time_datetime_cast() -> None:
-    s = pl.Series([time(10, 0, 0), time(11, 30, 59)])
-    with pytest.raises(pl.ComputeError, match=r"cannot cast `Time` to `Datetime`"):
-        s.cast(pl.Datetime)
-
-
-def test_err_on_invalid_time_zone_cast() -> None:
-    s = pl.Series([datetime(2021, 1, 1)])
-    with pytest.raises(pl.ComputeError, match=r"unable to parse time zone: 'qwerty'"):
-        s.cast(pl.Datetime("us", "qwerty"))
-
-
-def test_invalid_inner_type_cast_list() -> None:
-    s = pl.Series([[-1, 1]])
-    with pytest.raises(
-        pl.InvalidOperationError,
-        match=r"cannot cast List inner type: 'Int64' to Categorical",
-    ):
-        s.cast(pl.List(pl.Categorical))
-
-
 def test_lit_agg_err() -> None:
     with pytest.raises(pl.ComputeError, match=r"cannot aggregate a literal"):
         pl.DataFrame({"y": [1]}).with_columns(pl.lit(1).sum().over("y"))