MAINT: Relax check that a correct type is already set

This allows running `xpress` on current master. `xpress` copies the
type from `np.dtype(object)` rather than using `&PyArrayDescr_Type`.
That seems overall fine, we can just replace it.
The only reason for this check is to ensure that the user does not
override our updated `type(user_dtype)` and thus corrupting it.

1 files changed, 18 insertions, 4 deletions

diff --git a/numpy/core/src/multiarray/dtypemeta.c b/numpy/core/src/multiarray/dtypemeta.c
index c483f9937..ae1dfdd81 100644
--- a/numpy/core/src/multiarray/dtypemeta.c
+++ b/numpy/core/src/multiarray/dtypemeta.c
@@ -312,14 +312,28 @@ string_known_scalar_types(
 NPY_NO_EXPORT int
 dtypemeta_wrap_legacy_descriptor(PyArray_Descr *descr)
 {
-    if (Py_TYPE(descr) != &PyArrayDescr_Type) {
+    int has_type_set = Py_TYPE(descr) == &PyArrayDescr_Type;
+
+    if (!has_type_set) {
+        /* Accept if the type was filled in from an existing builtin dtype */
+        for (int i = 0; i < NPY_NTYPES; i++) {
+            PyArray_Descr *builtin = PyArray_DescrFromType(i);
+            has_type_set = Py_TYPE(descr) == Py_TYPE(builtin);
+            Py_DECREF(builtin);
+            if (has_type_set) {
+                break;
+            }
+        }
+    }
+    if (!has_type_set) {
         PyErr_Format(PyExc_RuntimeError,
                 "During creation/wrapping of legacy DType, the original class "
                 "was not of PyArrayDescr_Type (it is replaced in this step). "
                 "The extension creating a custom DType for type %S must be "
-                "modified to ensure `Py_TYPE(descr) == &PyArrayDescr_Type` at "
-                "registration time.",
-                descr->typeobj);
+                "modified to ensure `Py_TYPE(descr) == &PyArrayDescr_Type` or "
+                "that of an existing dtype (with the assumption it is just "
+                "copied over and can be replaced).",
+                descr->typeobj, Py_TYPE(descr));
         return -1;
     }