refactor: collapse try_cast_to_type into cast_to_type kwarg

The previous commit exposed cast_to_type and try_cast_to_type as two
separate pyo3 bindings and unified them in the Python wrapper via a
try_cast kwarg. That left try_cast_to_type in datafusion._internal
without a matching public Python name, breaking
test_datafusion_missing_exports.

Move the dispatch into the rust binding: cast_to_type now takes a
try_cast kwarg and selects between functions::expr_fn::cast_to_type
and try_cast_to_type internally. Only one pyo3 binding is registered,
so the wrapper-coverage check passes and the Python entrypoint is
unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: timsaucer

crates/core/src/functions.rs

@@ -609,8 +609,15 @@ expr_fn!(arrow_typeof, arg_1);
 expr_fn!(arrow_cast, arg_1 datatype);
 expr_fn!(arrow_try_cast, arg_1 datatype);
 expr_fn!(arrow_field, arg_1);
-expr_fn!(cast_to_type, arg_1 reference);
-expr_fn!(try_cast_to_type, arg_1 reference);
+#[pyfunction]
+#[pyo3(signature = (arg_1, reference, *, try_cast = false))]
+fn cast_to_type(arg_1: PyExpr, reference: PyExpr, try_cast: bool) -> PyExpr {
+    if try_cast {
+        functions::expr_fn::try_cast_to_type(arg_1.into(), reference.into()).into()
+    } else {
+        functions::expr_fn::cast_to_type(arg_1.into(), reference.into()).into()
+    }
+}
 expr_fn_vec!(arrow_metadata);
 expr_fn_vec!(with_metadata);
 expr_fn!(union_tag, arg1);
@@ -970,7 +977,6 @@ pub(crate) fn init_module(m: &Bound<'_, PyModule>) -> PyResult<()> {
     m.add_wrapped(wrap_pyfunction!(arrow_try_cast))?;
     m.add_wrapped(wrap_pyfunction!(arrow_field))?;
     m.add_wrapped(wrap_pyfunction!(cast_to_type))?;
-    m.add_wrapped(wrap_pyfunction!(try_cast_to_type))?;
     m.add_wrapped(wrap_pyfunction!(arrow_metadata))?;
     m.add_wrapped(wrap_pyfunction!(with_metadata))?;
     m.add_wrapped(wrap_pyfunction!(ascii))?;

python/datafusion/functions.py

@@ -2982,8 +2982,7 @@ def cast_to_type(value: Expr, type_ref: Expr, *, try_cast: bool = False) -> Expr
     Only the *type* of ``type_ref`` is used; its value is ignored. This is
     useful when the target type comes from another column or expression
     rather than being known up-front. When ``try_cast=True``, casts that
-    fail produce NULL instead of erroring (this dispatches to upstream
-    ``try_cast_to_type``).
+    fail produce NULL instead of erroring.
 
     Examples:
         >>> ctx = dfn.SessionContext()
@@ -3005,9 +3004,7 @@ def cast_to_type(value: Expr, type_ref: Expr, *, try_cast: bool = False) -> Expr
         >>> result.collect_column("c")[0].as_py() is None
         True
     """
-    if try_cast:
-        return Expr(f.try_cast_to_type(value.expr, type_ref.expr))
-    return Expr(f.cast_to_type(value.expr, type_ref.expr))
+    return Expr(f.cast_to_type(value.expr, type_ref.expr, try_cast=try_cast))
 
 
 def arrow_metadata(expr: Expr, key: Expr | str | None = None) -> Expr: