[Data] Fix: Replace bare raise with TypeError in string concatenation

python/ray/data/_internal/planner/plan_expression/expression_evaluator.py

@@ -97,11 +97,15 @@ def _pa_decode_dict_string_array(x: Union[pa.Array, pa.ChunkedArray]) -> Any:
 def _to_pa_string_input(x: Any) -> Any:
     if isinstance(x, str):
         return pa.scalar(x)
-    elif _is_pa_string_like(x) and isinstance(x, (pa.Array, pa.ChunkedArray)):
-        x = _pa_decode_dict_string_array(x)
-    else:
-        raise
-    return x
+    if isinstance(x, (pa.Array, pa.ChunkedArray)) and _is_pa_string_like(x):
+        return _pa_decode_dict_string_array(x)
+    actual_type = (
+        str(x.type) if isinstance(x, (pa.Array, pa.ChunkedArray)) else type(x).__name__
+    )
+    raise TypeError(
+        "Expected string or string-like pyarrow Array/ChunkedArray for string "
+        f"concatenation, got {actual_type}."
+    )
 
 
 def _pa_add_or_concat(left: Any, right: Any) -> Any:

python/ray/data/tests/unit/expressions/test_arithmetic.py

@@ -12,6 +12,7 @@
 import math
 
 import pandas as pd
+import pyarrow as pa
 import pytest
 from pkg_resources import parse_version
 
@@ -76,6 +77,13 @@ def test_reverse_addition(self, sample_data):
             result.reset_index(drop=True), expected, check_names=False
         )
 
+    def test_string_concat_invalid_input_type(self):
+        """Reject non-string-like inputs in string concatenation."""
+        table = pa.table({"name": ["a", "b"], "age": [1, 2]})
+        expr = col("name") + col("age")
+        with pytest.raises(TypeError, match="string-like pyarrow.*int64"):
+            eval_expr(expr, table)
+
     # ── Subtraction ──
 
     @pytest.mark.parametrize(