add docs and actually create scalar columns

crates/polars-core/src/chunked_array/builder/binary_offset.rs

@@ -0,0 +1,51 @@
+use super::*;
+
+pub struct BinaryOffsetChunkedBuilder {
+    pub(crate) chunk_builder: MutableBinaryArray<i64>,
+    pub(crate) field: FieldRef,
+}
+
+impl Clone for BinaryOffsetChunkedBuilder {
+    fn clone(&self) -> Self {
+        Self {
+            chunk_builder: self.chunk_builder.clone(),
+            field: self.field.clone(),
+        }
+    }
+}
+
+impl BinaryOffsetChunkedBuilder {
+    /// Create a new [`BinaryOffsetChunkedBuilder`]
+    ///
+    /// # Arguments
+    ///
+    /// * `capacity` - Number of string elements in the final array.
+    pub fn new(name: PlSmallStr, capacity: usize) -> Self {
+        Self {
+            chunk_builder: MutableBinaryArray::with_capacity(capacity),
+            field: Arc::new(Field::new(name, DataType::BinaryOffset)),
+        }
+    }
+
+    /// Appends a value of type `T` into the builder
+    #[inline]
+    pub fn append_value(&mut self, v: &[u8]) {
+        self.chunk_builder.push(Some(v));
+    }
+
+    /// Appends a null slot into the builder
+    #[inline]
+    pub fn append_null(&mut self) {
+        self.chunk_builder.push_null()
+    }
+
+    #[inline]
+    pub fn append_option(&mut self, opt: Option<&[u8]>) {
+        self.chunk_builder.push(opt);
+    }
+
+    pub fn finish(mut self) -> BinaryOffsetChunked {
+        let arr = self.chunk_builder.as_box();
+        ChunkedArray::new_with_compute_len(self.field, vec![arr])
+    }
+}

crates/polars-core/src/chunked_array/builder/mod.rs

@@ -1,3 +1,4 @@
+mod binary_offset;
 mod boolean;
 #[cfg(feature = "dtype-array")]
 pub mod fixed_size_list;
@@ -10,6 +11,7 @@ use std::sync::Arc;
 
 use arrow::array::*;
 use arrow::bitmap::Bitmap;
+pub use binary_offset::*;
 pub use boolean::*;
 #[cfg(feature = "dtype-array")]
 pub(crate) use fixed_size_list::*;

crates/polars-core/src/datatypes/any_value.rs

@@ -910,7 +910,7 @@ impl<'a> AnyValue<'a> {
             Object(v) => ObjectOwned(OwnedObject(v.to_boxed())),
             #[cfg(feature = "dtype-struct")]
             Struct(idx, arr, fields) => {
-                let avs = struct_to_avs_static(idx, arr, fields);
+                let avs = struct_to_avs_static(idx, arr, fields)?;
                 StructOwned(Box::new((avs, fields.to_vec())))
             },
             #[cfg(feature = "dtype-struct")]
@@ -1222,7 +1222,11 @@ impl TotalEq for AnyValue<'_> {
 }
 
 #[cfg(feature = "dtype-struct")]
-fn struct_to_avs_static(idx: usize, arr: &StructArray, fields: &[Field]) -> Vec<AnyValue<'static>> {
+fn struct_to_avs_static(
+    idx: usize,
+    arr: &StructArray,
+    fields: &[Field],
+) -> PolarsResult<Vec<AnyValue<'static>>> {
     let arrs = arr.values();
     let mut avs = Vec::with_capacity(arrs.len());
     // amortize loop counter
@@ -1231,10 +1235,10 @@ fn struct_to_avs_static(idx: usize, arr: &StructArray, fields: &[Field]) -> Vec<
             let arr = &**arrs.get_unchecked_release(i);
             let field = fields.get_unchecked_release(i);
             let av = arr_to_any_value(arr, idx, &field.dtype);
-            avs.push_unchecked(av.into_static().unwrap());
+            avs.push_unchecked(av.into_static()?);
         }
     }
-    avs
+    Ok(avs)
 }
 
 #[cfg(feature = "dtype-categorical")]