[arrow-pyarrow]: restore nicer pyarrow-arrow error message

arrow-pyarrow-testing/tests/pyarrow.rs

@@ -42,7 +42,10 @@ use arrow_array::{
     Array, ArrayRef, BinaryViewArray, Int32Array, RecordBatch, StringArray, StringViewArray,
 };
 use arrow_pyarrow::{FromPyArrow, ToPyArrow};
+use pyo3::exceptions::PyTypeError;
+use pyo3::types::{PyAnyMethods, PyModule};
 use pyo3::Python;
+use std::ffi::CString;
 use std::sync::Arc;
 
 #[test]
@@ -94,6 +97,34 @@ fn test_to_pyarrow_byte_view() {
     }
 }
 
+#[test]
+fn test_from_pyarrow_non_tuple() {
+    Python::initialize();
+
+    Python::attach(|py| {
+        let code = CString::new(
+            r#"
+class NotATuple:
+    def __arrow_c_array__(self):
+        return 1
+
+value = NotATuple()
+"#,
+        )
+        .unwrap();
+
+        let module = PyModule::from_code(py, code.as_c_str(), c"test.py", c"test_module").unwrap();
+        let value = module.getattr("value").unwrap();
+
+        let err = RecordBatch::from_pyarrow_bound(&value).unwrap_err();
+        assert!(err.is_instance_of::<PyTypeError>(py));
+        assert_eq!(
+            err.to_string(),
+            "TypeError: Expected __arrow_c_array__ to return a tuple of (schema, array) capsules."
+        );
+    });
+}
+
 fn binary_view_column(num_variadic_buffers: usize) -> BinaryViewArray {
     let long_scalar = b"but soft what light through yonder window breaks".as_slice();
     let mut builder = BinaryViewBuilder::new().with_fixed_block_size(long_scalar.len() as u32);

arrow-pyarrow/src/lib.rs

@@ -149,6 +149,24 @@ fn validate_pycapsule(capsule: &Bound<PyCapsule>, name: &str) -> PyResult<()> {
     Ok(())
 }
 
+fn extract_arrow_c_array_capsules<'py>(
+    value: &Bound<'py, PyAny>,
+) -> PyResult<(Bound<'py, PyCapsule>, Bound<'py, PyCapsule>)> {
+    let tuple = value.call_method0("__arrow_c_array__")?;
+
+    if !tuple.is_instance_of::<PyTuple>() {
+        return Err(PyTypeError::new_err(
+            "Expected __arrow_c_array__ to return a tuple of (schema, array) capsules.",
+        ));
+    }
+
+    tuple.extract().map_err(|_| {
+        PyTypeError::new_err(
+            "Expected __arrow_c_array__ to return a tuple of (schema, array) capsules.",
+        )
+    })
+}
+
 impl FromPyArrow for DataType {
     fn from_pyarrow_bound(value: &Bound<PyAny>) -> PyResult<Self> {
         // Newer versions of PyArrow as well as other libraries with Arrow data implement this
@@ -245,8 +263,7 @@ impl FromPyArrow for ArrayData {
         // method, so prefer it over _export_to_c.
         // See https://arrow.apache.org/docs/format/CDataInterface/PyCapsuleInterface.html
         if value.hasattr("__arrow_c_array__")? {
-            let (schema_capsule, array_capsule) =
-                value.call_method0("__arrow_c_array__")?.extract()?;
+            let (schema_capsule, array_capsule) = extract_arrow_c_array_capsules(value)?;
 
             validate_pycapsule(&schema_capsule, "arrow_schema")?;
             validate_pycapsule(&array_capsule, "arrow_array")?;
@@ -324,8 +341,7 @@ impl FromPyArrow for RecordBatch {
         // See https://arrow.apache.org/docs/format/CDataInterface/PyCapsuleInterface.html
 
         if value.hasattr("__arrow_c_array__")? {
-            let (schema_capsule, array_capsule) =
-                value.call_method0("__arrow_c_array__")?.extract()?;
+            let (schema_capsule, array_capsule) = extract_arrow_c_array_capsules(value)?;
 
             validate_pycapsule(&schema_capsule, "arrow_schema")?;
             validate_pycapsule(&array_capsule, "arrow_array")?;