Fix test case to be platform independent, note ARROW-1345. Improve quality of error message

Change-Id: I3bef642f3620396ea728b54fefe780b915d8fc32

Author: wesm

cpp/src/arrow/python/numpy-internal.h

@@ -64,6 +64,41 @@ class Ndarray1DIndexer {
   int64_t stride_;
 };
 
+static inline std::string GetNumPyTypeName(int npy_type) {
+#define TYPE_CASE(TYPE, NAME) \
+  case NPY_##TYPE:            \
+    return NAME;
+
+  switch (npy_type) {
+    TYPE_CASE(BOOL, "bool")
+    TYPE_CASE(INT8, "int8")
+    TYPE_CASE(INT16, "int16")
+    TYPE_CASE(INT32, "int32")
+    TYPE_CASE(INT64, "int64")
+#if (NPY_INT64 != NPY_LONGLONG)
+    TYPE_CASE(LONGLONG, "longlong")
+#endif
+    TYPE_CASE(UINT8, "uint8")
+    TYPE_CASE(UINT16, "uint16")
+    TYPE_CASE(UINT32, "uint32")
+    TYPE_CASE(UINT64, "uint64")
+#if (NPY_UINT64 != NPY_ULONGLONG)
+    TYPE_CASE(ULONGLONG, "ulonglong")
+#endif
+    TYPE_CASE(FLOAT16, "float16")
+    TYPE_CASE(FLOAT32, "float32")
+    TYPE_CASE(FLOAT64, "float64")
+    TYPE_CASE(DATETIME, "datetime64")
+    TYPE_CASE(OBJECT, "object")
+    TYPE_CASE(VOID, "void")
+    default:
+      break;
+  }
+
+#undef TYPE_CASE
+  return "unrecognized type in GetNumPyTypeName";
+}
+
 }  // namespace py
 }  // namespace arrow
 

cpp/src/arrow/python/pandas_to_arrow.cc

@@ -151,8 +151,12 @@ Status CheckFlatNumpyArray(PyArrayObject* numpy_array, int np_type) {
     return Status::Invalid("only handle 1-dimensional arrays");
   }
 
-  if (PyArray_DESCR(numpy_array)->type_num != np_type) {
-    return Status::Invalid("can only handle exact conversions");
+  const int received_type = PyArray_DESCR(numpy_array)->type_num;
+  if (received_type != np_type) {
+    std::stringstream ss;
+    ss << "trying to convert NumPy type " << GetNumPyTypeName(np_type) << " but got "
+       << GetNumPyTypeName(received_type);
+    return Status::Invalid(ss.str());
   }
 
   return Status::OK();

python/pyarrow/error.pxi

@@ -65,7 +65,7 @@ cdef int check_status(const CStatus& status) nogil except -1:
         return 0
 
     with gil:
-        message = frombytes(status.ToString())
+        message = frombytes(status.message())
         if status.IsInvalid():
             raise ArrowInvalid(message)
         elif status.IsIOError():
@@ -85,4 +85,5 @@ cdef int check_status(const CStatus& status) nogil except -1:
         elif status.IsPlasmaStoreFull():
             raise PlasmaStoreFull(message)
         else:
+            message = frombytes(status.ToString())
             raise ArrowException(message)

python/pyarrow/includes/common.pxd

@@ -42,6 +42,7 @@ cdef extern from "arrow/api.h" namespace "arrow" nogil:
         CStatus()
 
         c_string ToString()
+        c_string message()
 
         c_bool ok()
         c_bool IsIOError()

python/pyarrow/tests/pandas_examples.py

@@ -99,7 +99,8 @@ def dataframe_with_lists(include_index=False):
         [0, 1, 2, 3, 4],
         None,
         [0],
-        np.array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9] * 2)[::2]
+        np.array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9] * 2,
+                 dtype=np.int64)[::2]
     ]
     fields.append(pa.field('double', pa.list_(pa.float64())))
     arrays['double'] = [