changeset:   101030:eef8f72ddb00
branch:      2.7
parent:      101020:879da9400529
user:        Martin Panter <vadmium+py@gmail.com>
date:        Sun Jan 31 06:30:56 2016 +0000
files:       Lib/test/test_extcall.py Misc/NEWS Python/ceval.c
description:
Issue #4806: Avoid masking TypeError when *-unpacking a generator

Based on patch by Hagen Fürstenau.


diff -r 879da9400529 -r eef8f72ddb00 Lib/test/test_extcall.py
--- a/Lib/test/test_extcall.py	Sat Apr 16 14:47:12 2016 -0700
+++ b/Lib/test/test_extcall.py	Sun Jan 31 06:30:56 2016 +0000
@@ -93,7 +93,7 @@
     >>> g(*Nothing())
     Traceback (most recent call last):
       ...
-    TypeError: g() argument after * must be a sequence, not instance
+    TypeError: g() argument after * must be an iterable, not instance
 
     >>> class Nothing:
     ...     def __len__(self): return 5
@@ -102,7 +102,7 @@
     >>> g(*Nothing())
     Traceback (most recent call last):
       ...
-    TypeError: g() argument after * must be a sequence, not instance
+    TypeError: g() argument after * must be an iterable, not instance
 
     >>> class Nothing():
     ...     def __len__(self): return 5
@@ -128,6 +128,17 @@
     >>> g(*Nothing())
     0 (1, 2, 3) {}
 
+Check for issue #4806: Does a TypeError in a generator get propagated with the
+right error message?
+
+    >>> def broken(): raise TypeError("myerror")
+    ...
+
+    >>> g(*(broken() for i in range(1)))
+    Traceback (most recent call last):
+      ...
+    TypeError: myerror
+
 Make sure that the function doesn't stomp the dictionary
 
     >>> d = {'a': 1, 'b': 2, 'c': 3}
@@ -167,17 +178,17 @@
     >>> h(*h)
     Traceback (most recent call last):
       ...
-    TypeError: h() argument after * must be a sequence, not function
+    TypeError: h() argument after * must be an iterable, not function
 
     >>> dir(*h)
     Traceback (most recent call last):
       ...
-    TypeError: dir() argument after * must be a sequence, not function
+    TypeError: dir() argument after * must be an iterable, not function
 
     >>> None(*h)
     Traceback (most recent call last):
       ...
-    TypeError: NoneType object argument after * must be a sequence, \
+    TypeError: NoneType object argument after * must be an iterable, \
 not function
 
     >>> h(**h)
diff -r 879da9400529 -r eef8f72ddb00 Misc/NEWS
--- a/Misc/NEWS	Sat Apr 16 14:47:12 2016 -0700
+++ b/Misc/NEWS	Sun Jan 31 06:30:56 2016 +0000
@@ -10,6 +10,10 @@
 Core and Builtins
 -----------------
 
+- Issue #4806: Avoid masking the original TypeError exception when using star
+  (*) unpacking and the exception was raised from a generator.  Based on
+  patch by Hagen Fürstenau.
+
 - Issue #26659: Make the builtin slice type support cycle collection.
 
 - Issue #26718: super.__init__ no longer leaks memory if called multiple times.
diff -r 879da9400529 -r eef8f72ddb00 Python/ceval.c
--- a/Python/ceval.c	Sat Apr 16 14:47:12 2016 -0700
+++ b/Python/ceval.c	Sun Jan 31 06:30:56 2016 +0000
@@ -4615,10 +4615,12 @@
             PyObject *t = NULL;
             t = PySequence_Tuple(stararg);
             if (t == NULL) {
-                if (PyErr_ExceptionMatches(PyExc_TypeError)) {
+                if (PyErr_ExceptionMatches(PyExc_TypeError) &&
+                        /* Don't mask TypeError raised from a generator */
+                        !PyGen_Check(stararg)) {
                     PyErr_Format(PyExc_TypeError,
                                  "%.200s%.200s argument after * "
-                                 "must be a sequence, not %200s",
+                                 "must be an iterable, not %200s",
                                  PyEval_GetFuncName(func),
                                  PyEval_GetFuncDesc(func),
                                  stararg->ob_type->tp_name);