Merge python#7

7: Add warnings for sorting and comparison r=ltratt a=nanjekyejoannah

Most of the warnings are covered on the list sort method.

I added the missing warnings for the `cmp` and `__cmp__` method.

This replaces python#4 

Co-authored-by: Joannah Nanjekye <jnanjekye@python.org>

Include/warnings.h

@@ -7,6 +7,7 @@ extern "C" {
 PyAPI_FUNC(void) _PyWarnings_Init(void);
 
 PyAPI_FUNC(int) PyErr_WarnEx(PyObject *, const char *, Py_ssize_t);
+PyAPI_FUNC(int) PyErr_WarnEx_WithFix(PyObject *, const char *, const char *, Py_ssize_t);
 PyAPI_FUNC(int) PyErr_WarnExplicit(PyObject *, const char *, const char *, int,
                                     const char *, PyObject *);
 PyAPI_FUNC(int) PyErr_WarnExplicit_WithFix(PyObject *, const char *, const char *, const char *, int,

Lib/test/test_sort.py

@@ -278,6 +278,11 @@ def test_main(verbose=None):
             ("the cmp argument is not supported", DeprecationWarning)):
         test_support.run_unittest(*test_classes)
 
+    with test_support.check_py3k_warnings(
+            ("the cmp method is not supported in 3.x"
+             "implement the function to a utility library", Py3xWarning)):
+        test_support.run_unittest(*test_classes)
+
         # verify reference counting
         if verbose and hasattr(sys, "gettotalrefcount"):
             import gc

Objects/object.c

@@ -860,6 +860,13 @@ PyObject_Compare(PyObject *v, PyObject *w)
 {
     int result;
 
+    if (Py_Py3kWarningFlag &&
+        PyErr_WarnEx_WithFix(PyExc_Py3xWarning, "the cmp method is not supported in 3.x",
+        "you can either provide your own alternative or use a third party library with a "
+         "backwards compatible fix", 1) < 0) {
+        return 0;
+    }
+
     if (v == NULL || w == NULL) {
         PyErr_BadInternalCall();
         return -1;

Python/_warnings.c

@@ -817,6 +817,23 @@ do_warn(PyObject *message, PyObject *category, Py_ssize_t stack_level)
     return res;
 }
 
+static PyObject *
+do_warn_with_fix(PyObject *message, PyObject *fix, PyObject *category, Py_ssize_t stack_level)
+{
+    PyObject *filename, *module, *registry, *res;
+    int lineno;
+
+    if (!setup_context(stack_level, &filename, &lineno, &module, &registry))
+        return NULL;
+
+    res = warn_explicit_with_fix(category, message, fix, filename, lineno, module, registry,
+                        NULL);
+    Py_DECREF(filename);
+    Py_DECREF(registry);
+    Py_DECREF(module);
+    return res;
+}
+
 static PyObject *
 warnings_warn(PyObject *self, PyObject *args, PyObject *kwds)
 {
@@ -1029,8 +1046,28 @@ PyErr_WarnEx(PyObject *category, const char *text, Py_ssize_t stack_level)
     return 0;
 }
 
-/* PyErr_Warn is only for backwards compatibility and will be removed.
-   Use PyErr_WarnEx instead. */
+/* Function to issue a warning message; may raise an exception. */
+int
+PyErr_WarnEx_WithFix(PyObject *category, const char *text, const char *fix_txt, Py_ssize_t stack_level)
+{
+    PyObject *res;
+    PyObject *message = PyString_FromString(text);
+    PyObject *fix = PyString_FromString(fix_txt);
+    if (message == NULL)
+        return -1;
+
+    if (category == NULL)
+        category = PyExc_RuntimeWarning;
+
+    res = do_warn_with_fix(message, fix, category, stack_level);
+    Py_DECREF(message);
+    Py_DECREF(fix);
+    if (res == NULL)
+        return -1;
+    Py_DECREF(res);
+
+    return 0;
+}
 
 #undef PyErr_Warn