fix: Full null on dyn int (pola-rs#16679)

Wouittone · Jun 22, 2024 · 92928fd · 92928fd
1 parent 13b54c9
commit 92928fd
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diff --git a/crates/polars-core/src/datatypes/dtype.rs b/crates/polars-core/src/datatypes/dtype.rs
@@ -28,6 +28,18 @@ pub enum UnknownKind {
     Any,
 }
 
+impl UnknownKind {
+    pub fn materialize(&self) -> Option<DataType> {
+        let dtype = match self {
+            UnknownKind::Int(v) => materialize_dyn_int(*v).dtype(),
+            UnknownKind::Float => DataType::Float64,
+            UnknownKind::Str => DataType::String,
+            UnknownKind::Any => return None,
+        };
+        Some(dtype)
+    }
+}
+
 #[derive(Clone, Debug)]
 pub enum DataType {
     Boolean,

diff --git a/crates/polars-core/src/series/ops/null.rs b/crates/polars-core/src/series/ops/null.rs
@@ -54,6 +54,10 @@ impl Series {
                 StructChunked::new(name, &fields).unwrap().into_series()
             },
             DataType::Null => Series::new_null(name, size),
+            DataType::Unknown(kind) => {
+                let dtype = kind.materialize().expect("expected known type");
+                Series::full_null(name, size, &dtype)
+            },
             _ => {
                 macro_rules! primitive {
                     ($type:ty) => {{

diff --git a/py-polars/tests/unit/test_empty.py b/py-polars/tests/unit/test_empty.py
@@ -132,3 +132,8 @@ def test_empty_is_in() -> None:
 @pytest.mark.parametrize("method", ["drop_nulls", "unique"])
 def test_empty_to_empty(method: str) -> None:
     assert getattr(pl.DataFrame(), method)().shape == (0, 0)
+
+
+def test_empty_shift_over_16676() -> None:
+    df = pl.DataFrame({"a": [], "b": []})
+    assert df.with_columns(pl.col("a").shift(fill_value=0).over("b")).shape == (0, 2)