Merge pull request #16133 from seberg/maint-cast-error

MAINT: Unify casting error creation (outside the iterator)

13 files changed, 89 insertions, 148 deletions

diff --git a/numpy/core/src/multiarray/array_assign_array.c b/numpy/core/src/multiarray/array_assign_array.c
index e40b6c719..b8dc7d516 100644
--- a/numpy/core/src/multiarray/array_assign_array.c
+++ b/numpy/core/src/multiarray/array_assign_array.c
@@ -305,19 +305,8 @@ PyArray_AssignArray(PyArrayObject *dst, PyArrayObject *src,
     /* Check the casting rule */
     if (!PyArray_CanCastTypeTo(PyArray_DESCR(src),
                                 PyArray_DESCR(dst), casting)) {
-        PyObject *errmsg;
-        errmsg = PyUString_FromString("Cannot cast scalar from ");
-        PyUString_ConcatAndDel(&errmsg,
-                PyObject_Repr((PyObject *)PyArray_DESCR(src)));
-        PyUString_ConcatAndDel(&errmsg,
-                PyUString_FromString(" to "));
-        PyUString_ConcatAndDel(&errmsg,
-                PyObject_Repr((PyObject *)PyArray_DESCR(dst)));
-        PyUString_ConcatAndDel(&errmsg,
-                PyUString_FromFormat(" according to the rule %s",
-                        npy_casting_to_string(casting)));
-        PyErr_SetObject(PyExc_TypeError, errmsg);
-        Py_DECREF(errmsg);
+        npy_set_invalid_cast_error(
+                PyArray_DESCR(src), PyArray_DESCR(dst), casting, NPY_FALSE);
         goto fail;
     }
 
diff --git a/numpy/core/src/multiarray/array_assign_scalar.c b/numpy/core/src/multiarray/array_assign_scalar.c
index 6bc9bcfee..41eb75f1c 100644
--- a/numpy/core/src/multiarray/array_assign_scalar.c
+++ b/numpy/core/src/multiarray/array_assign_scalar.c
@@ -203,19 +203,8 @@ PyArray_AssignRawScalar(PyArrayObject *dst,
     /* Check the casting rule */
     if (!can_cast_scalar_to(src_dtype, src_data,
                             PyArray_DESCR(dst), casting)) {
-        PyObject *errmsg;
-        errmsg = PyUString_FromString("Cannot cast scalar from ");
-        PyUString_ConcatAndDel(&errmsg,
-                PyObject_Repr((PyObject *)src_dtype));
-        PyUString_ConcatAndDel(&errmsg,
-                PyUString_FromString(" to "));
-        PyUString_ConcatAndDel(&errmsg,
-                PyObject_Repr((PyObject *)PyArray_DESCR(dst)));
-        PyUString_ConcatAndDel(&errmsg,
-                PyUString_FromFormat(" according to the rule %s",
-                        npy_casting_to_string(casting)));
-        PyErr_SetObject(PyExc_TypeError, errmsg);
-        Py_DECREF(errmsg);
+        npy_set_invalid_cast_error(
+                src_dtype, PyArray_DESCR(dst), casting, NPY_TRUE);
         return -1;
     }
 
diff --git a/numpy/core/src/multiarray/convert_datatype.c b/numpy/core/src/multiarray/convert_datatype.c
index d59a62ed8..0390c92fc 100644
--- a/numpy/core/src/multiarray/convert_datatype.c
+++ b/numpy/core/src/multiarray/convert_datatype.c
@@ -985,6 +985,54 @@ PyArray_CanCastArrayTo(PyArrayObject *arr, PyArray_Descr *to,
     return PyArray_CanCastTypeTo(from, to, casting);
 }
 
+
+NPY_NO_EXPORT const char *
+npy_casting_to_string(NPY_CASTING casting)
+{
+    switch (casting) {
+        case NPY_NO_CASTING:
+            return "'no'";
+        case NPY_EQUIV_CASTING:
+            return "'equiv'";
+        case NPY_SAFE_CASTING:
+            return "'safe'";
+        case NPY_SAME_KIND_CASTING:
+            return "'same_kind'";
+        case NPY_UNSAFE_CASTING:
+            return "'unsafe'";
+        default:
+            return "<unknown>";
+    }
+}
+
+
+/**
+ * Helper function to set a useful error when casting is not possible.
+ *
+ * @param src_dtype
+ * @param dst_dtype
+ * @param casting
+ * @param scalar Whether this was a "scalar" cast (includes 0-D array with
+ *               PyArray_CanCastArrayTo result).
+ */
+NPY_NO_EXPORT void
+npy_set_invalid_cast_error(
+        PyArray_Descr *src_dtype, PyArray_Descr *dst_dtype,
+        NPY_CASTING casting, npy_bool scalar)
+{
+    char *msg;
+
+    if (!scalar) {
+        msg = "Cannot cast array data from %R to %R according to the rule %s";
+    }
+    else {
+        msg = "Cannot cast scalar from %R to %R according to the rule %s";
+    }
+    PyErr_Format(PyExc_TypeError,
+            msg, src_dtype, dst_dtype, npy_casting_to_string(casting));
+}
+
+
 /*NUMPY_API
  * See if array scalars can be cast.
  *
diff --git a/numpy/core/src/multiarray/convert_datatype.h b/numpy/core/src/multiarray/convert_datatype.h
index 72867ead8..4a7d85187 100644
--- a/numpy/core/src/multiarray/convert_datatype.h
+++ b/numpy/core/src/multiarray/convert_datatype.h
@@ -22,6 +22,14 @@ NPY_NO_EXPORT int
 should_use_min_scalar(npy_intp narrs, PyArrayObject **arr,
                       npy_intp ndtypes, PyArray_Descr **dtypes);
 
+NPY_NO_EXPORT const char *
+npy_casting_to_string(NPY_CASTING casting);
+
+NPY_NO_EXPORT void
+npy_set_invalid_cast_error(
+        PyArray_Descr *src_dtype, PyArray_Descr *dst_dtype,
+        NPY_CASTING casting, npy_bool scalar);
+
 /*
  * This function calls Py_DECREF on flex_dtype, and replaces it with
  * a new dtype that has been adapted based on the values in data_dtype
diff --git a/numpy/core/src/multiarray/ctors.c b/numpy/core/src/multiarray/ctors.c
index 12bf9eace..df92544fd 100644
--- a/numpy/core/src/multiarray/ctors.c
+++ b/numpy/core/src/multiarray/ctors.c
@@ -21,7 +21,6 @@
 #include "shape.h"
 #include "npy_buffer.h"
 #include "lowlevel_strided_loops.h"
-#include "methods.h"
 #include "_datetime.h"
 #include "datetime_strings.h"
 #include "array_assign.h"
@@ -2181,42 +2180,9 @@ PyArray_FromArray(PyArrayObject *arr, PyArray_Descr *newtype, int flags)
 
     /* Raise an error if the casting rule isn't followed */
     if (!PyArray_CanCastArrayTo(arr, newtype, casting)) {
-        PyObject *errmsg;
-        PyArray_Descr *arr_descr = NULL;
-        PyObject *arr_descr_repr = NULL;
-        PyObject *newtype_repr = NULL;
-
         PyErr_Clear();
-        errmsg = PyUString_FromString("Cannot cast array data from ");
-        arr_descr = PyArray_DESCR(arr);
-        if (arr_descr == NULL) {
-            Py_DECREF(newtype);
-            Py_DECREF(errmsg);
-            return NULL;
-        }
-        arr_descr_repr = PyObject_Repr((PyObject *)arr_descr);
-        if (arr_descr_repr == NULL) {
-            Py_DECREF(newtype);
-            Py_DECREF(errmsg);
-            return NULL;
-        }
-        PyUString_ConcatAndDel(&errmsg, arr_descr_repr);
-        PyUString_ConcatAndDel(&errmsg,
-                PyUString_FromString(" to "));
-        newtype_repr = PyObject_Repr((PyObject *)newtype);
-        if (newtype_repr == NULL) {
-            Py_DECREF(newtype);
-            Py_DECREF(errmsg);
-            return NULL;
-        }
-        PyUString_ConcatAndDel(&errmsg, newtype_repr);
-        PyUString_ConcatAndDel(&errmsg,
-                PyUString_FromFormat(" according to the rule %s",
-                        npy_casting_to_string(casting)));
-        PyErr_SetObject(PyExc_TypeError, errmsg);
-        Py_DECREF(errmsg);
-
-        Py_DECREF(newtype);
+        npy_set_invalid_cast_error(
+                PyArray_DESCR(arr), newtype, casting, PyArray_NDIM(arr) == 0);
         return NULL;
     }
 
diff --git a/numpy/core/src/multiarray/datetime.c b/numpy/core/src/multiarray/datetime.c
index 67ed3ca85..cfe801898 100644
--- a/numpy/core/src/multiarray/datetime.c
+++ b/numpy/core/src/multiarray/datetime.c
@@ -22,9 +22,9 @@
 
 #include "common.h"
 #include "numpy/arrayscalars.h"
-#include "methods.h"
 #include "_datetime.h"
 #include "datetime_strings.h"
+#include "convert_datatype.h"
 
 /*
  * Computes the python `ret, d = divmod(d, unit)`.
diff --git a/numpy/core/src/multiarray/datetime_strings.c b/numpy/core/src/multiarray/datetime_strings.c
index 4574c05d8..f847c7ea8 100644
--- a/numpy/core/src/multiarray/datetime_strings.c
+++ b/numpy/core/src/multiarray/datetime_strings.c
@@ -20,7 +20,7 @@
 #include "npy_pycompat.h"
 
 #include "numpy/arrayscalars.h"
-#include "methods.h"
+#include "convert_datatype.h"
 #include "_datetime.h"
 #include "datetime_strings.h"
 
diff --git a/numpy/core/src/multiarray/methods.c b/numpy/core/src/multiarray/methods.c
index 29ae49c18..e2026ec1c 100644
--- a/numpy/core/src/multiarray/methods.c
+++ b/numpy/core/src/multiarray/methods.c
@@ -789,24 +789,6 @@ array_setscalar(PyArrayObject *self, PyObject *args)
     }
 }
 
-NPY_NO_EXPORT const char *
-npy_casting_to_string(NPY_CASTING casting)
-{
-    switch (casting) {
-        case NPY_NO_CASTING:
-            return "'no'";
-        case NPY_EQUIV_CASTING:
-            return "'equiv'";
-        case NPY_SAFE_CASTING:
-            return "'safe'";
-        case NPY_SAME_KIND_CASTING:
-            return "'same_kind'";
-        case NPY_UNSAFE_CASTING:
-            return "'unsafe'";
-        default:
-            return "<unknown>";
-    }
-}
 
 static PyObject *
 array_astype(PyArrayObject *self, PyObject *args, PyObject *kwds)
@@ -876,19 +858,8 @@ array_astype(PyArrayObject *self, PyObject *args, PyObject *kwds)
         return (PyObject *)ret;
     }
     else {
-        PyObject *errmsg;
-        errmsg = PyUString_FromString("Cannot cast array from ");
-        PyUString_ConcatAndDel(&errmsg,
-                PyObject_Repr((PyObject *)PyArray_DESCR(self)));
-        PyUString_ConcatAndDel(&errmsg,
-                PyUString_FromString(" to "));
-        PyUString_ConcatAndDel(&errmsg,
-                PyObject_Repr((PyObject *)dtype));
-        PyUString_ConcatAndDel(&errmsg,
-                PyUString_FromFormat(" according to the rule %s",
-                        npy_casting_to_string(casting)));
-        PyErr_SetObject(PyExc_TypeError, errmsg);
-        Py_DECREF(errmsg);
+        npy_set_invalid_cast_error(
+                PyArray_DESCR(self), dtype, casting, PyArray_NDIM(self) == 0);
         Py_DECREF(dtype);
         return NULL;
     }
diff --git a/numpy/core/src/multiarray/methods.h b/numpy/core/src/multiarray/methods.h
index 7a9a24a00..c0de23c35 100644
--- a/numpy/core/src/multiarray/methods.h
+++ b/numpy/core/src/multiarray/methods.h
@@ -5,8 +5,6 @@
 
 extern NPY_NO_EXPORT PyMethodDef array_methods[];
 
-NPY_NO_EXPORT const char *
-npy_casting_to_string(NPY_CASTING casting);
 
 /*
  * Pathlib support, takes a borrowed reference and returns a new one.
diff --git a/numpy/core/src/multiarray/nditer_constr.c b/numpy/core/src/multiarray/nditer_constr.c
index e40a2d594..620c7d593 100644
--- a/numpy/core/src/multiarray/nditer_constr.c
+++ b/numpy/core/src/multiarray/nditer_constr.c
@@ -1308,21 +1308,11 @@ npyiter_check_casting(int nop, PyArrayObject **op,
                         !PyArray_CanCastArrayTo(op[iop],
                                           op_dtype[iop],
                                           casting)) {
-                PyObject *errmsg;
-                errmsg = PyUString_FromFormat(
-                        "Iterator operand %d dtype could not be cast from ",
-                        iop);
-                PyUString_ConcatAndDel(&errmsg,
-                        PyObject_Repr((PyObject *)PyArray_DESCR(op[iop])));
-                PyUString_ConcatAndDel(&errmsg,
-                        PyUString_FromString(" to "));
-                PyUString_ConcatAndDel(&errmsg,
-                        PyObject_Repr((PyObject *)op_dtype[iop]));
-                PyUString_ConcatAndDel(&errmsg,
-                        PyUString_FromFormat(" according to the rule %s",
-                                npyiter_casting_to_string(casting)));
-                PyErr_SetObject(PyExc_TypeError, errmsg);
-                Py_DECREF(errmsg);
+                PyErr_Format(PyExc_TypeError,
+                        "Iterator operand %d dtype could not be cast from "
+                        "%R to %R according to the rule %s",
+                        iop, PyArray_DESCR(op[iop]), op_dtype[iop],
+                        npyiter_casting_to_string(casting));
                 return 0;
             }
             /* Check write (temp -> op) casting */
@@ -1330,22 +1320,12 @@ npyiter_check_casting(int nop, PyArrayObject **op,
                         !PyArray_CanCastTypeTo(op_dtype[iop],
                                           PyArray_DESCR(op[iop]),
                                           casting)) {
-                PyObject *errmsg;
-                errmsg = PyUString_FromString(
-                        "Iterator requested dtype could not be cast from ");
-                PyUString_ConcatAndDel(&errmsg,
-                        PyObject_Repr((PyObject *)op_dtype[iop]));
-                PyUString_ConcatAndDel(&errmsg,
-                        PyUString_FromString(" to "));
-                PyUString_ConcatAndDel(&errmsg,
-                        PyObject_Repr((PyObject *)PyArray_DESCR(op[iop])));
-                PyUString_ConcatAndDel(&errmsg,
-                        PyUString_FromFormat(", the operand %d dtype, "
-                                "according to the rule %s",
-                                iop,
-                                npyiter_casting_to_string(casting)));
-                PyErr_SetObject(PyExc_TypeError, errmsg);
-                Py_DECREF(errmsg);
+                PyErr_Format(PyExc_TypeError,
+                        "Iterator requested dtype could not be cast from "
+                        "%R to %R, the operand %d dtype, "
+                        "according to the rule %s",
+                        op_dtype[iop], PyArray_DESCR(op[iop]), iop,
+                        npyiter_casting_to_string(casting));
                 return 0;
             }
 
diff --git a/numpy/core/src/umath/ufunc_type_resolution.c b/numpy/core/src/umath/ufunc_type_resolution.c
index 2534ff78a..ea20bb24f 100644
--- a/numpy/core/src/umath/ufunc_type_resolution.c
+++ b/numpy/core/src/umath/ufunc_type_resolution.c
@@ -51,25 +51,6 @@ npy_casting_to_py_object(NPY_CASTING casting)
 }
 
 
-static const char *
-npy_casting_to_string(NPY_CASTING casting)
-{
-    switch (casting) {
-        case NPY_NO_CASTING:
-            return "'no'";
-        case NPY_EQUIV_CASTING:
-            return "'equiv'";
-        case NPY_SAFE_CASTING:
-            return "'safe'";
-        case NPY_SAME_KIND_CASTING:
-            return "'same_kind'";
-        case NPY_UNSAFE_CASTING:
-            return "'unsafe'";
-        default:
-            return "<unknown>";
-    }
-}
-
 /**
  * Always returns -1 to indicate the exception was raised, for convenience
  */
diff --git a/numpy/core/tests/test_api.py b/numpy/core/tests/test_api.py
index b3f7cc88a..2600d409a 100644
--- a/numpy/core/tests/test_api.py
+++ b/numpy/core/tests/test_api.py
@@ -1,6 +1,7 @@
 import sys
 
 import numpy as np
+from numpy.core._rational_tests import rational
 import pytest
 from numpy.testing import (
      assert_, assert_equal, assert_array_equal, assert_raises, assert_warns,
@@ -141,6 +142,16 @@ def test_array_array():
     assert_equal(np.array([(1.0,) * 10] * 10, dtype=np.float64),
                  np.ones((10, 10), dtype=np.float64))
 
+@pytest.mark.parametrize("array", [True, False])
+def test_array_impossible_casts(array):
+    # All builtin types can forst cast as least theoretically
+    # but user dtypes cannot necessarily.
+    rt = rational(1, 2)
+    if array:
+        rt = np.array(rt)
+    with assert_raises(ValueError):
+        np.array(rt, dtype="M8")
+
 
 def test_fastCopyAndTranspose():
     # 0D array
diff --git a/numpy/doc/structured_arrays.py b/numpy/doc/structured_arrays.py
index 72990cf89..359d4f7f4 100644
--- a/numpy/doc/structured_arrays.py
+++ b/numpy/doc/structured_arrays.py
@@ -341,7 +341,7 @@ structured datatype has just a single field::
  >>> nostruct[:] = twofield
  Traceback (most recent call last):
  ...
- TypeError: Cannot cast scalar from dtype([('A', '<i4'), ('B', '<i4')]) to dtype('int32') according to the rule 'unsafe'
+ TypeError: Cannot cast array data from dtype([('A', '<i4'), ('B', '<i4')]) to dtype('int32') according to the rule 'unsafe'
 
 Assignment from other Structured Arrays
 ```````````````````````````````````````