BUG: test, fix flexible dtype conversion on class with __array__ (numpy#15076)

Fixes issue numpygh-12256 where

import numpy as np
class MyArray:
    def __array__(self, result=None):
        return np.array(['0'*70], dtype=object)
    
np.array(MyArray(), dtype=str)
# has dtype U64, not U70
The problem was the result of obj.__array__ was not used when filling out a flexible dtype "by-value".

I also renamed a test file, over time we should move the tests related to array protocol into it.


* BUG: test, fix flexible dtype conversion on class with __array__

* Update numpy/core/_add_newdocs.py

Thanks for the correction

Co-Authored-By: Eric Wieser <[email protected]>

Co-authored-by: Eric Wieser <[email protected]>

Author: 2 people

numpy/core/_add_newdocs.py

@@ -2507,7 +2507,7 @@
 
 
 add_newdoc('numpy.core.multiarray', 'ndarray', ('__array__',
-    """ a.__array__(|dtype) -> reference if type unchanged, copy otherwise.
+    """ a.__array__([dtype], /) -> reference if type unchanged, copy otherwise.
 
     Returns either a new reference to self if dtype is not given or a new array
     of provided data type if dtype is different from the current dtype of the
@@ -6871,4 +6871,3 @@ def add_newdoc_for_scalar_type(obj, fixed_aliases, doc):
         >>> np.{ftype}(-.25).as_integer_ratio()
         (-1, 4)
         """.format(ftype=float_name)))
-

numpy/core/src/multiarray/ctors.c

@@ -1909,7 +1909,7 @@ PyArray_FromAny(PyObject *op, PyArray_Descr *newtype, int min_depth,
 
     /* If the requested dtype is flexible, adapt it */
     if (newtype != NULL) {
-        newtype = PyArray_AdaptFlexibleDType(op,
+        newtype = PyArray_AdaptFlexibleDType((arr == NULL) ? op : (PyObject *)arr,
                     (dtype == NULL) ? PyArray_DESCR(arr) : dtype,
                     newtype);
         if (newtype == NULL) {

numpy/core/tests/test_issue14735.py

@@ -0,0 +1,44 @@
+import pytest
+import warnings
+import numpy as np
+
+
+@pytest.mark.filterwarnings("error")
+def test_getattr_warning():
+    # issue gh-14735: make sure we clear only getattr errors, and let warnings
+    # through
+    class Wrapper:
+        def __init__(self, array):
+            self.array = array
+
+        def __len__(self):
+            return len(self.array)
+
+        def __getitem__(self, item):
+            return type(self)(self.array[item])
+
+        def __getattr__(self, name):
+            if name.startswith("__array_"):
+                warnings.warn("object got converted", UserWarning, stacklevel=1)
+
+            return getattr(self.array, name)
+
+        def __repr__(self):
+            return "<Wrapper({self.array})>".format(self=self)
+
+    array = Wrapper(np.arange(10))
+    with pytest.raises(UserWarning, match="object got converted"):
+        np.asarray(array)
+
+
+def test_array_called():
+    class Wrapper:
+        val = '0' * 100
+        def __array__(self, result=None):
+            return np.array([self.val], dtype=object)
+
+
+    wrapped = Wrapper()
+    arr = np.array(wrapped, dtype=str)
+    assert arr.dtype == 'U100'
+    assert arr[0] == Wrapper.val