Merge pull request #12447 from ahaldane/unrevert_multifield_view

ENH: add back the multifield copy->view change

3 files changed, 7 insertions, 69 deletions

diff --git a/numpy/core/src/multiarray/arrayobject.c b/numpy/core/src/multiarray/arrayobject.c
index 936a30426..97aaee93d 100644
--- a/numpy/core/src/multiarray/arrayobject.c
+++ b/numpy/core/src/multiarray/arrayobject.c
@@ -656,11 +656,9 @@ array_might_be_written(PyArrayObject *obj)
 {
     const char *msg =
         "Numpy has detected that you (may be) writing to an array returned\n"
-        "by numpy.diagonal or by selecting multiple fields in a structured\n"
-        "array. This code will likely break in a future numpy release --\n"
-        "see numpy.diagonal or arrays.indexing reference docs for details.\n"
-        "The quick fix is to make an explicit copy (e.g., do\n"
-        "arr.diagonal().copy() or arr[['f0','f1']].copy()).";
+        "by numpy.diagonal. This code will likely break in a future numpy\n"
+        "release -- see numpy.diagonal docs for details. The quick fix is\n"
+        "to make an explicit copy (e.g., do arr.diagonal().copy()).";
     if (PyArray_FLAGS(obj) & NPY_ARRAY_WARN_ON_WRITE) {
         /* 2012-07-17, 1.7 */
         if (DEPRECATE_FUTUREWARNING(msg) < 0) {
diff --git a/numpy/core/src/multiarray/convert.c b/numpy/core/src/multiarray/convert.c
index e88582a51..7db467308 100644
--- a/numpy/core/src/multiarray/convert.c
+++ b/numpy/core/src/multiarray/convert.c
@@ -614,22 +614,6 @@ PyArray_View(PyArrayObject *self, PyArray_Descr *type, PyTypeObject *pytype)
     }
 
     dtype = PyArray_DESCR(self);
-
-    if (type != NULL && !PyArray_EquivTypes(dtype, type) &&
-            (PyArray_FLAGS(self) & NPY_ARRAY_WARN_ON_WRITE)) {
-        const char *msg =
-            "Numpy has detected that you may be viewing or writing to an array "
-            "returned by selecting multiple fields in a structured array. \n\n"
-            "This code may break in numpy 1.16 because this will return a view "
-            "instead of a copy -- see release notes for details.";
-        /* 2016-09-19, 1.12 */
-        if (DEPRECATE_FUTUREWARNING(msg) < 0) {
-            return NULL;
-        }
-        /* Only warn once per array */
-        PyArray_CLEARFLAGS(self, NPY_ARRAY_WARN_ON_WRITE);
-    }
-
     flags = PyArray_FLAGS(self);
 
     Py_INCREF(dtype);
diff --git a/numpy/core/src/multiarray/mapping.c b/numpy/core/src/multiarray/mapping.c
index d371ae762..1b05faeeb 100644
--- a/numpy/core/src/multiarray/mapping.c
+++ b/numpy/core/src/multiarray/mapping.c
@@ -1389,54 +1389,14 @@ array_subscript_asarray(PyArrayObject *self, PyObject *op)
 }
 
 /*
- * Helper function for _get_field_view which turns a multifield
- * view into a "packed" copy, as done in numpy 1.15 and before.
- * In numpy 1.16 this function should be removed.
- */
-NPY_NO_EXPORT int
-_multifield_view_to_copy(PyArrayObject **view) {
-    static PyObject *copyfunc = NULL;
-    PyObject *viewcopy;
-
-    /* return a repacked copy of the view */
-    npy_cache_import("numpy.lib.recfunctions", "repack_fields", &copyfunc);
-    if (copyfunc == NULL) {
-        goto view_fail;
-    }
-
-    PyArray_CLEARFLAGS(*view, NPY_ARRAY_WARN_ON_WRITE);
-    viewcopy = PyObject_CallFunction(copyfunc, "O", *view);
-    if (viewcopy == NULL) {
-        goto view_fail;
-    }
-    Py_DECREF(*view);
-    *view = (PyArrayObject*)viewcopy;
-
-    /* warn when writing to the copy */
-    PyArray_ENABLEFLAGS(*view, NPY_ARRAY_WARN_ON_WRITE);
-    return 0;
-
-view_fail:
-    Py_DECREF(*view);
-    *view = NULL;
-    return 0;
-}
-
-/*
  * Attempts to subscript an array using a field name or list of field names.
  *
  * If an error occurred, return 0 and set view to NULL. If the subscript is not
  * a string or list of strings, return -1 and set view to NULL. Otherwise
  * return 0 and set view to point to a new view into arr for the given fields.
- *
- * In numpy 1.15 and before, in the case of a list of field names the returned
- * view will actually be a copy by default, with fields packed together.
- * The `force_view` argument causes a view to be returned. This argument can be
- * removed in 1.16 when we plan to return a view always.
  */
 NPY_NO_EXPORT int
-_get_field_view(PyArrayObject *arr, PyObject *ind, PyArrayObject **view,
-                int force_view)
+_get_field_view(PyArrayObject *arr, PyObject *ind, PyArrayObject **view)
 {
     *view = NULL;
 
@@ -1597,11 +1557,7 @@ _get_field_view(PyArrayObject *arr, PyObject *ind, PyArrayObject **view,
             return 0;
         }
 
-        /* the code below can be replaced by "return 0" in 1.16 */
-        if (force_view) {
-            return 0;
-        }
-        return _multifield_view_to_copy(view);
+        return 0;
     }
     return -1;
 }
@@ -1629,7 +1585,7 @@ array_subscript(PyArrayObject *self, PyObject *op)
     /* return fields if op is a string index */
     if (PyDataType_HASFIELDS(PyArray_DESCR(self))) {
         PyArrayObject *view;
-        int ret = _get_field_view(self, op, &view, 0);
+        int ret = _get_field_view(self, op, &view);
         if (ret == 0){
             if (view == NULL) {
                 return NULL;
@@ -1911,7 +1867,7 @@ array_assign_subscript(PyArrayObject *self, PyObject *ind, PyObject *op)
     /* field access */
     if (PyDataType_HASFIELDS(PyArray_DESCR(self))){
         PyArrayObject *view;
-        int ret = _get_field_view(self, ind, &view, 1);
+        int ret = _get_field_view(self, ind, &view);
         if (ret == 0){
             if (view == NULL) {
                 return -1;