MAINT: revert __skip_array_function__ from NEP-18

xref GH-13624, GH-12028

TODO: update tests/CI for NUMPY_EXPERIMENTAL_ARRAY_FUNCTION=0

1 files changed, 22 insertions, 1 deletions

diff --git a/numpy/core/overrides.py b/numpy/core/overrides.py
index ad4d1c721..347e71bd4 100644
--- a/numpy/core/overrides.py
+++ b/numpy/core/overrides.py
@@ -1,6 +1,7 @@
 """Implementation of __array_function__ overrides from NEP-18."""
 import collections
 import functools
+import os
 import textwrap
 
 from numpy.core._multiarray_umath import (
@@ -8,6 +9,10 @@ from numpy.core._multiarray_umath import (
 from numpy.compat._inspect import getargspec
 
 
+ENABLE_ARRAY_FUNCTION = bool(
+    int(os.environ.get('NUMPY_EXPERIMENTAL_ARRAY_FUNCTION', 1)))
+
+
 add_docstring(
     implement_array_function,
     """
@@ -137,6 +142,22 @@ def array_function_dispatch(dispatcher, module=None, verify=True,
     Function suitable for decorating the implementation of a NumPy function.
     """
 
+    if not ENABLE_ARRAY_FUNCTION:
+        def decorator(implementation):
+            if docs_from_dispatcher:
+                add_docstring(implementation, dispatcher.__doc__)
+
+            public_api = implementation
+
+            if module is not None:
+                public_api.__module__ = module
+
+            public_api._implementation = implementation
+
+            return public_api
+
+        return decorator
+
     def decorator(implementation):
         if verify:
             verify_matching_signatures(implementation, dispatcher)
@@ -172,7 +193,7 @@ def array_function_dispatch(dispatcher, module=None, verify=True,
         if module is not None:
             public_api.__module__ = module
 
-        public_api.__skip_array_function__ = implementation
+        public_api._implementation = implementation
 
         return public_api