MAINT: make __array__ raise on python < 3.12

Otherwise, on python 3.11 and below, np.array(array_api_strict_array)
becomes a 0D object array.

Author: ev-br

array_api_strict/_array_object.py

@@ -165,13 +165,21 @@ def __repr__(self) -> str:
     # Instead of `__array__` we now implement the buffer protocol.
     # Note that it makes array-apis-strict requiring python>=3.12
     def __buffer__(self, flags):
-        print('__buffer__')
         if self._device != CPU_DEVICE:
             raise RuntimeError(f"Can not convert array on the '{self._device}' device to a Numpy array.")
         return memoryview(self._array)
     def __release_buffer(self, buffer):
-        print('__release__')
         # XXX anything to do here?
+        pass
+
+    def __array__(self, *args, **kwds):
+        # a stub for python < 3.12; otherwise numpy silently produces object arrays
+        import sys
+        minor, major = sys.version_info.minor, sys.version_info.major
+        if major < 3 or minor < 12:
+            raise TypeError(
+                "Interoperation with NumPy requires python >= 3.12. Please upgrade."
+            )
 
     # These are various helper functions to make the array behavior match the
     # spec in places where it either deviates from or is more strict than

array_api_strict/tests/test_array_object.py

@@ -541,9 +541,23 @@ def test_array_conversion():
 
     for device in ("device1", "device2"):
         a = ones((2, 3), device=array_api_strict.Device(device))
-        with pytest.raises(RuntimeError, match="Can not convert array"):
+        with pytest.raises((RuntimeError, ValueError)):
             np.asarray(a)
 
+    # __buffer__ should work for now for conversion to numpy
+    a = ones((2, 3))
+    na = np.array(a)
+    assert na.shape == (2, 3)
+    assert na.dtype == np.float64
+
+@pytest.mark.skipif(not sys.version_info.major*100 + sys.version_info.minor < 312,
+                    reason="conversion to numpy errors out unless python >= 3.12"
+)
+def test_array_conversion_2():
+    a = ones((2, 3))
+    with pytest.raises(TypeError):
+        np.array(a)
+
 
 def test_allow_newaxis():
     a = ones(5)