BUG: Fix crash on non-void structured array repr

Fixes gh-9821

2 files changed, 29 insertions, 7 deletions

diff --git a/numpy/core/arrayprint.py b/numpy/core/arrayprint.py
index 62f967131..3554fe3c4 100644
--- a/numpy/core/arrayprint.py
+++ b/numpy/core/arrayprint.py
@@ -365,9 +365,6 @@ def _get_format_function(data, **options):
     find the right formatting function for the dtype_
     """
     dtype_ = data.dtype
-    if dtype_.fields is not None:
-        return StructureFormat.from_data(data, **options)
-
     dtypeobj = dtype_.type
     formatdict = _get_formatdict(data, **options)
     if issubclass(dtypeobj, _nt.bool_):
@@ -394,7 +391,10 @@ def _get_format_function(data, **options):
     elif issubclass(dtypeobj, _nt.object_):
         return formatdict['object']()
     elif issubclass(dtypeobj, _nt.void):
-        return formatdict['void']()
+        if dtype_.names is not None:
+            return StructuredVoidFormat.from_data(data, **options)
+        else:
+            return formatdict['void']()
     else:
         return formatdict['numpystr']()
 
@@ -1164,14 +1164,21 @@ class SubArrayFormat(object):
         return "[" + ", ".join(self.__call__(a) for a in arr) + "]"
 
 
-class StructureFormat(object):
+class StructuredVoidFormat(object):
+    """
+    Formatter for structured np.void objects.
+
+    This does not work on structured alias types like np.dtype(('i4', 'i2,i2')),
+    as alias scalars lose their field information, and the implementation
+    relies upon np.void.__getitem__.
+    """
     def __init__(self, format_functions):
         self.format_functions = format_functions
 
     @classmethod
     def from_data(cls, data, **options):
         """
-        This is a second way to initialize StructureFormat, using the raw data
+        This is a second way to initialize StructuredVoidFormat, using the raw data
         as input. Added to avoid changing the signature of __init__.
         """
         format_functions = []
@@ -1192,13 +1199,24 @@ class StructureFormat(object):
         else:
             return "({})".format(", ".join(str_fields))
 
+
+# for backwards compatibility
+class StructureFormat(StructuredVoidFormat):
+    def __init__(self, *args, **kwargs):
+        # NumPy 1.14, 2018-02-14
+        warnings.warn(
+            "StructureFormat has been replaced by StructuredVoidFormat",
+            DeprecationWarning, stacklevel=2)
+        super(StructureFormat, self).__init__(*args, **kwargs)
+
+
 def _void_scalar_repr(x):
     """
     Implements the repr for structured-void scalars. It is called from the
     scalartypes.c.src code, and is placed here because it uses the elementwise
     formatters defined above.
     """
-    return StructureFormat.from_data(array(x), **_format_options)(x)
+    return StructuredVoidFormat.from_data(array(x), **_format_options)(x)
 
 
 _typelessdata = [int_, float_, complex_, bool_]
diff --git a/numpy/core/tests/test_multiarray.py b/numpy/core/tests/test_multiarray.py
index d80eaf8d5..f17fa573e 100644
--- a/numpy/core/tests/test_multiarray.py
+++ b/numpy/core/tests/test_multiarray.py
@@ -483,6 +483,10 @@ class TestDtypedescr(object):
         dt_int = np.dtype(('i4', fields))
         assert_equal(str(dt_int), "(numpy.int32, [('a', '<i2'), ('b', '<i2')])")
 
+        # gh-9821
+        arr_int = np.zeros(4, dt_int)
+        assert_equal(repr(arr_int), "array([0, 0, 0, 0])")
+
 
 class TestZeroRank(object):
     def setup(self):