Issue #28410: Added _PyErr_FormatFromCause() -- the helper for raising

new exception with setting current exception as __cause__.

_PyErr_FormatFromCause(exception, format, args...) is equivalent to Python

    raise exception(format % args) from sys.exc_info()[1]

3 files changed, 14 insertions, 47 deletions

diff --git a/Objects/abstract.c b/Objects/abstract.c
index 747eda0..f9afece 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -2198,20 +2198,18 @@ _Py_CheckFunctionResult(PyObject *func, PyObject *result, const char *where)
     }
     else {
         if (err_occurred) {
-            PyObject *exc, *val, *tb;
-            PyErr_Fetch(&exc, &val, &tb);
-
             Py_DECREF(result);
 
-            if (func)
-                PyErr_Format(PyExc_SystemError,
-                             "%R returned a result with an error set",
-                             func);
-            else
-                PyErr_Format(PyExc_SystemError,
-                             "%s returned a result with an error set",
-                             where);
-            _PyErr_ChainExceptions(exc, val, tb);
+            if (func) {
+                _PyErr_FormatFromCause(PyExc_SystemError,
+                        "%R returned a result with an error set",
+                        func);
+            }
+            else {
+                _PyErr_FormatFromCause(PyExc_SystemError,
+                        "%s returned a result with an error set",
+                        where);
+            }
 #ifdef Py_DEBUG
             /* Ensure that the bug is caught in debug mode */
             Py_FatalError("a function returned a result with an error set");
diff --git a/Objects/genobject.c b/Objects/genobject.c
index 7a1e9fd..7bcf016 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -118,33 +118,6 @@ gen_dealloc(PyGenObject *gen)
     PyObject_GC_Del(gen);
 }
 
-static void
-gen_chain_runtime_error(const char *msg)
-{
-    PyObject *exc, *val, *val2, *tb;
-
-    /* TODO: This about rewriting using _PyErr_ChainExceptions. */
-
-    PyErr_Fetch(&exc, &val, &tb);
-    PyErr_NormalizeException(&exc, &val, &tb);
-    if (tb != NULL) {
-        PyException_SetTraceback(val, tb);
-    }
-
-    Py_DECREF(exc);
-    Py_XDECREF(tb);
-
-    PyErr_SetString(PyExc_RuntimeError, msg);
-    PyErr_Fetch(&exc, &val2, &tb);
-    PyErr_NormalizeException(&exc, &val2, &tb);
-
-    Py_INCREF(val);
-    PyException_SetCause(val2, val);
-    PyException_SetContext(val2, val);
-
-    PyErr_Restore(exc, val2, tb);
-}
-
 static PyObject *
 gen_send_ex(PyGenObject *gen, PyObject *arg, int exc, int closing)
 {
@@ -276,8 +249,7 @@ gen_send_ex(PyGenObject *gen, PyObject *arg, int exc, int closing)
             else if PyAsyncGen_CheckExact(gen) {
                 msg = "async generator raised StopIteration";
             }
-            /* Raise a RuntimeError */
-            gen_chain_runtime_error(msg);
+            _PyErr_FormatFromCause(PyExc_RuntimeError, "%s", msg);
         }
         else {
             /* `gen` is an ordinary generator without
@@ -309,7 +281,7 @@ gen_send_ex(PyGenObject *gen, PyObject *arg, int exc, int closing)
            raise a RuntimeError.
         */
         const char *msg = "async generator raised StopAsyncIteration";
-        gen_chain_runtime_error(msg);
+        _PyErr_FormatFromCause(PyExc_RuntimeError, "%s", msg);
     }
 
     if (!result || f->f_stacktop == NULL) {
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index adeec8c..80e6cf2 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -3835,13 +3835,10 @@ PyUnicode_DecodeFSDefaultAndSize(const char *s, Py_ssize_t size)
                                 Py_FileSystemDefaultEncodeErrors);
 #ifdef MS_WINDOWS
         if (!res && PyErr_ExceptionMatches(PyExc_UnicodeDecodeError)) {
-            PyObject *exc, *val, *tb;
-            PyErr_Fetch(&exc, &val, &tb);
-            PyErr_Format(PyExc_RuntimeError,
-                "filesystem path bytes were not correctly encoded with '%s'. " \
+            _PyErr_FormatFromCause(PyExc_RuntimeError,
+                "filesystem path bytes were not correctly encoded with '%s'. "
                 "Please report this at http://bugs.python.org/issue27781",
                 Py_FileSystemDefaultEncoding);
-            _PyErr_ChainExceptions(exc, val, tb);
         }
 #endif
         return res;