Feature: Add DType::FixedSizeList variant (#4371)

Adds the variant `DType::FixedSizeList`, but without most of the
implementations. The `unimplemented!`s and `TODO(connor)[FixedSizeList]`
will be fixed in later PRs.

Also fixes a bug and incorrect tests with `list_empty` in
`vortex-scalar`, where creating an empty list made a null scalar.

Finally, adds some more casting tests in `vortex-scalar` (which found a
bug in `vortex-scalar/src/scalar.rs` where the logic did not work for
nested scalars).

(Tracking Issue incoming soon)

Signed-off-by: Connor Tsui <[email protected]>

Author: connortsui20

encodings/sparse/src/canonical.rs

@@ -88,6 +88,9 @@ impl CanonicalVTable<SparseVTable> for SparseVTable {
                     *nullability,
                 )
             }
+            DType::FixedSizeList(..) => {
+                unimplemented!("TODO(connor)[FixedSizeList]")
+            }
             DType::Extension(_ext_dtype) => todo!(),
         }
     }

fuzz/src/array/compare.rs

@@ -116,6 +116,7 @@ pub fn compare_canonical_array(
             )
             .into_array())
         }
+        DType::FixedSizeList(..) => unimplemented!("TODO(connor)[FixedSizeList]"),
         d @ (DType::Null | DType::Extension(_)) => {
             unreachable!("DType {d} not supported for fuzzing")
         }

fuzz/src/array/filter.rs

@@ -108,6 +108,7 @@ pub fn filter_canonical_array(array: &dyn Array, filter: &[bool]) -> VortexResul
             }
             take_canonical_array_non_nullable_indices(array, indices.as_slice())
         }
+        DType::FixedSizeList(..) => unimplemented!("TODO(connor)[FixedSizeList]"),
         d @ (DType::Null | DType::Extension(_)) => {
             unreachable!("DType {d} not supported for fuzzing")
         }

fuzz/src/array/search_sorted.rs

@@ -124,6 +124,7 @@ pub fn search_sorted_canonical_array(
             let scalar_vals = (0..array.len()).map(|i| array.scalar_at(i)).collect_vec();
             Ok(scalar_vals.search_sorted(&scalar.cast(array.dtype())?, side))
         }
+        DType::FixedSizeList(..) => unimplemented!("TODO(connor)[FixedSizeList]"),
         d @ (DType::Null | DType::Extension(_)) => {
             unreachable!("DType {d} not supported for fuzzing")
         }

fuzz/src/array/slice.rs

@@ -86,6 +86,7 @@ pub fn slice_canonical_array(
             .into_array();
             ListArray::try_new(elements, offsets, validity).map(|a| a.into_array())
         }
+        DType::FixedSizeList(..) => unimplemented!("TODO(connor)[FixedSizeList]"),
         DType::Decimal(decimal_dtype, _) => {
             let decimal_array = array.to_decimal()?;
             Ok(

fuzz/src/array/sort.rs

@@ -81,6 +81,7 @@ pub fn sort_canonical_array(array: &dyn Array) -> VortexResult<ArrayRef> {
             });
             take_canonical_array_non_nullable_indices(array, &sort_indices)
         }
+        DType::FixedSizeList(..) => unimplemented!("TODO(connor)[FixedSizeList]"),
         d @ (DType::Null | DType::Extension(_)) => {
             unreachable!("DType {d} not supported for fuzzing")
         }

fuzz/src/array/take.rs

@@ -124,6 +124,7 @@ pub fn take_canonical_array(
             }
             Ok(builder.finish())
         }
+        DType::FixedSizeList(..) => unimplemented!("TODO(connor)[FixedSizeList]"),
         d @ (DType::Null | DType::Extension(_)) => {
             unreachable!("DType {d} not supported for fuzzing")
         }

vortex-array/src/arrays/arbitrary.rs

@@ -124,6 +124,9 @@ fn random_array(u: &mut Unstructured, dtype: &DType, len: Option<usize>) -> Resu
                     .into_array())
                 }
                 DType::List(ldt, n) => random_list(u, ldt, *n, chunk_len),
+                DType::FixedSizeList(..) => {
+                    unimplemented!("TODO(connor)[FixedSizeList]")
+                }
                 DType::Extension(..) => {
                     todo!("Extension arrays are not implemented")
                 }

vortex-array/src/arrays/constant/canonical.rs

@@ -128,6 +128,9 @@ impl CanonicalVTable<ConstantVTable> for ConstantVTable {
                     array.len(),
                 )?)
             }
+            DType::FixedSizeList(..) => {
+                unimplemented!("TODO(connor)[FixedSizeList]")
+            }
             DType::Extension(ext_dtype) => {
                 let s = ExtScalar::try_from(scalar)?;
 

vortex-array/src/builders/list.rs

@@ -276,14 +276,14 @@ mod tests {
     }
 
     #[test]
-    fn test_non_null_fails() {
+    fn test_append_empty_list() {
         let dtype: Arc<DType> = Arc::new(I32.into());
         let mut builder = ListBuilder::<u32>::with_capacity(dtype.clone(), NonNullable, 0);
 
         assert!(
             builder
                 .append_value(Scalar::list_empty(dtype, NonNullable).as_list())
-                .is_err()
+                .is_ok()
         )
     }