Expose some more internal types

src/common.rs

@@ -68,6 +68,7 @@ fn dict_key_type(d: &DataType) -> Option<DataType> {
     None
 }
 
+/// Parsed representation of a JSON path element.
 #[derive(Debug)]
 pub enum JsonPath<'s> {
     Key(&'s str),
@@ -97,13 +98,17 @@ impl From<i64> for JsonPath<'_> {
 }
 
 #[derive(Debug)]
-enum JsonPathArgs<'a> {
+pub enum JsonPathArgs<'a> {
     Array(&'a ArrayRef),
     Scalars(Vec<JsonPath<'a>>),
 }
 
 impl<'s> JsonPathArgs<'s> {
-    fn extract_path(path_args: &'s [ColumnarValue]) -> DataFusionResult<Self> {
+    /// Extract the JSON path from the arguments to a json function.
+    /// The path can be:
+    /// - A single array argument (`json_get(json_data, keys_column)`)
+    /// - One or more scalar arguments (`json_get(json_data, 'foo', 0)`)
+    pub fn extract_path(path_args: &'s [ColumnarValue]) -> DataFusionResult<Self> {
         // If there is a single argument as an array, we know how to handle it
         if let Some((ColumnarValue::Array(array), &[])) = path_args.split_first() {
             return Ok(Self::Array(array));

src/common_union.rs

@@ -101,6 +101,13 @@ impl JsonUnion {
     }
 }
 
+/// Get the `DataType` for a `JsonUnion`.
+/// This will be the data type of the result of `json_array->'field'`.
+#[must_use]
+pub fn json_union_data_type() -> DataType {
+    JsonUnion::data_type()
+}
+
 /// So we can do `collect::<JsonUnion>()`
 impl FromIterator<Option<JsonUnionField>> for JsonUnion {
     fn from_iter<I: IntoIterator<Item = Option<JsonUnionField>>>(iter: I) -> Self {

src/lib.rs

@@ -20,7 +20,9 @@ mod json_length;
 mod json_object_keys;
 mod rewrite;
 
-pub use common_union::{JsonUnionEncoder, JsonUnionValue};
+pub use common_union::{json_union_data_type, JsonUnionEncoder, JsonUnionValue};
+
+pub use common::JsonPath;
 
 pub mod functions {
     pub use crate::json_as_text::json_as_text;