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fix: Ensure number of names passed to struct.rename_fields is valid #15624

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fix: Ensure number of names passed to struct.rename_fields is valid #15624

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14 changes: 8 additions & 6 deletions crates/polars-plan/src/dsl/function_expr/struct_.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,24 +43,25 @@ impl StructFunction {
polars_bail!(StructFieldNotFound: "{}", name.as_ref());
}
}),
RenameFields(names) => mapper.map_dtype(|dt| match dt {
RenameFields(names) => mapper.try_map_dtype(|dt| match dt {
DataType::Struct(fields) => {
polars_ensure!(fields.len() == names.len(), ComputeError: "expected {} names, got {}", fields.len(), names.len());
let fields = fields
.iter()
.zip(names.as_ref())
.map(|(fld, name)| Field::new(name, fld.data_type().clone()))
.collect();
DataType::Struct(fields)
Ok(DataType::Struct(fields))
},
// The types will be incorrect, but its better than nothing
// we can get an incorrect type with python lambdas, because we only know return type when running
// the query
dt => DataType::Struct(
dt => Ok(DataType::Struct(
names
.iter()
.map(|name| Field::new(name, dt.clone()))
.collect(),
),
)),
}),
PrefixFields(prefix) => mapper.try_map_dtype(|dt| match dt {
DataType::Struct(fields) => {
Expand Down Expand Up @@ -131,8 +132,9 @@ pub(super) fn get_by_name(s: &Series, name: Arc<str>) -> PolarsResult<Series> {

pub(super) fn rename_fields(s: &Series, names: Arc<Vec<String>>) -> PolarsResult<Series> {
let ca = s.struct_()?;
let fields = ca
.fields()
let fields = ca.fields();
polars_ensure!(fields.len() == names.len(), ComputeError: "expected {} names, got {}", fields.len(), names.len());
let fields = fields
.iter()
.zip(names.as_ref())
.map(|(s, name)| {
Expand Down
15 changes: 15 additions & 0 deletions py-polars/tests/unit/datatypes/test_struct.py
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Original file line number Diff line number Diff line change
Expand Up @@ -868,3 +868,18 @@ def test_struct_null_count_10130() -> None:

s = pl.Series([{"a": None}])
assert s.null_count() == 1


def test_struct_rename_mismatch_9052() -> None:
df = pl.DataFrame({"A": [{"p": 1, "q": 2}]})

with pytest.raises(pl.ComputeError, match=r"expected 2 names, got 1"):
df.select(pl.col("A").struct.rename_fields(["x"]))

# Additional cases
# too many fields
with pytest.raises(pl.ComputeError, match=r"expected 2 names, got 3"):
df.select(pl.col("A").struct.rename_fields(["too", "many", "fields"]))
# during schema evaluation
with pytest.raises(pl.ComputeError, match=r"expected 2 names, got 1"):
df.lazy().select(pl.col("A").struct.rename_fields(["x"])).schema
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