DEP: Deprecate identity check in comparisons (not just removing)

Instead of just removing it, raise Deprecation/Future warnings
when the comparison object ufunc and the identity check do not
coincide.

1 files changed, 36 insertions, 3 deletions

diff --git a/numpy/core/src/umath/loops.c.src b/numpy/core/src/umath/loops.c.src
index c1e2dc1c5..c3abd02f8 100644
--- a/numpy/core/src/umath/loops.c.src
+++ b/numpy/core/src/umath/loops.c.src
@@ -2562,27 +2562,60 @@ NPY_NO_EXPORT void
 /**begin repeat
  * #kind = equal, not_equal, greater, greater_equal, less, less_equal#
  * #OP = EQ, NE, GT, GE, LT, LE#
+ * #identity = NPY_TRUE, NPY_FALSE, NPY_FALSE, NPY_TRUE, NPY_FALSE, NPY_TRUE#
  */
 NPY_NO_EXPORT void
 OBJECT_@kind@(char **args, npy_intp *dimensions, npy_intp *steps, void *NPY_UNUSED(func)) {
     BINARY_LOOP {
         PyObject *in1 = *(PyObject **)ip1;
         PyObject *in2 = *(PyObject **)ip2;
+        in1 = in1 ? in1 : Py_None;
+        in2 = in2 ? in2 : Py_None;
         /*
          * Do not use RichCompareBool because it includes an identity check.
          * But this is wrong for elementwise behaviour, since i.e. it says
          * that NaN can be equal to NaN, and an array is equal to itself.
          */
-        PyObject *ret_obj = PyObject_RichCompare(
-                            in1 ? in1 : Py_None,
-                            in2 ? in2 : Py_None, Py_@OP@);
+        PyObject *ret_obj = PyObject_RichCompare(in1, in2, Py_@OP@);
         if (ret_obj == NULL) {
+            if (in1 == in2) {
+                PyErr_Clear();
+                if (DEPRECATE("numpy @kind@ will not check object identity "
+                              "in the future. The comparison error will "
+                              "be raised.") < 0) {
+                    return;
+                }
+                *((npy_bool *)op1) = @identity@;
+                continue;
+            }
             return;
         }
         int ret = PyObject_IsTrue(ret_obj);
         if (ret == -1) {
+            if (in1 == in2) {
+                PyErr_Clear();
+                if (DEPRECATE("numpy @kind@ will not check object identity "
+                              "in the future. The error trying to get the "
+                              "boolean value of the comparison result will "
+                              "be raised.") < 0) {
+                    return;
+                }
+                *((npy_bool *)op1) = @identity@;
+                continue;
+            }
             return;
         }
+        if ((in1 == in2) && ((npy_bool)ret != @identity@)) {
+            if (DEPRECATE_FUTUREWARNING(
+                        "numpy @kind@ will not check object identity "
+                        "in the future. The comparison did not return the "
+                        "same result as suggested by the identity "
+                        "and will change.") < 0) {
+                return;
+            }
+            *((npy_bool *)op1) = @identity@;
+            continue;
+        }
         *((npy_bool *)op1) = (npy_bool)ret;
     }
 }