enable except-as target deletion only when language level is 3

Cython/Compiler/Parsing.py

@@ -1573,7 +1573,8 @@ def p_except_clause(s):
             exc_type = exc_type.args
         else:
             exc_type = [exc_type]
-        if s.sy == ',':
+        if s.sy == ',' or (s.sy == 'IDENT' and s.systring == 'as'
+                           and s.context.language_level == 2):
             s.next()
             exc_value = p_test(s)
         elif s.sy == 'IDENT' and s.systring == 'as':

tests/run/cython3.pyx

 # cython: language_level=3
 # mode: run
-# tag: generators, python3
+# tag: generators, python3, exceptions
 
 cimport cython
 
@@ -11,6 +11,11 @@ __doc__ = """
 a = 1
 b = 2
 x = u'abc'
+
+>>> except_as_deletes
+True
+>>> no_match_does_not_touch_target
+True
 """
 
 import sys
@@ -22,6 +27,115 @@ def locals_function(a, b=2):
     return locals()
 
 
+### module level except-as tests
+
+exc = [None]
+e = None
+try:
+    raise KeyError
+except AttributeError as e:
+    exc[0] = e
+except KeyError       as e:
+    exc[0] = e
+except IndexError     as e:
+    exc[0] = e
+except:
+    exc[0] = 'SOMETHING ELSE'
+
+try:
+    e
+except NameError:
+    except_as_deletes = True
+else:
+    except_as_deletes = False
+
+
+e = 123
+try:
+    raise TypeError
+except NameError as e:
+    pass
+except TypeError:
+    pass
+no_match_does_not_touch_target = (e == 123)
+
+
+### more except-as tests
+
+def except_as_raise_deletes_target(x, a):
+    """
+    >>> except_as_raise_deletes_target(None, TypeError)
+    1
+    1
+    >>> except_as_raise_deletes_target(TypeError('test'), TypeError)
+    Traceback (most recent call last):
+    UnboundLocalError: local variable 'b' referenced before assignment
+    >>> except_as_raise_deletes_target(ValueError('test'), TypeError)
+    Traceback (most recent call last):
+    ValueError: test
+    >>> except_as_raise_deletes_target(None, TypeError)
+    1
+    1
+    """
+    b = 1
+    try:
+        i = 1
+        if x:
+            raise x
+    except a as b:
+        i = 2
+        assert isinstance(b, a)
+    print(b)  # raises UnboundLocalError if except clause was executed
+    return i
+
+
+def except_as_raise_with_empty_except(x, a):
+    """
+    >>> except_as_raise_with_empty_except(None, TypeError)
+    >>> except_as_raise_with_empty_except(TypeError('test'), TypeError)
+    >>> except_as_raise_with_empty_except(ValueError('test'), TypeError)
+    Traceback (most recent call last):
+    ValueError: test
+    >>> except_as_raise_with_empty_except(None, TypeError)
+    """
+    try:
+        if x:
+            raise x
+        b = 1
+    except a as b:  # previously raised UnboundLocalError
+        pass
+
+
+def except_as_deletes_target_in_gen(x, a):
+    """
+    >>> list(except_as_deletes_target_in_gen(None, TypeError))
+    [(1, 1), (2, 1), (5, 1)]
+    >>> list(except_as_deletes_target_in_gen(TypeError('test'), TypeError))
+    [(1, 1), 3, 6]
+    >>> list(except_as_deletes_target_in_gen(ValueError('test'), TypeError))
+    [(1, 1), (4, 1), (5, 1)]
+    """
+    b = 1
+    try:
+        i = 1
+        yield (1, b)
+        if x:
+            raise x
+        yield (2, b)
+    except a as b:
+        i = 2
+        assert isinstance(b, a)
+        yield 3
+    except:
+        yield (4, b)
+    try:
+        yield (5, b)
+    except UnboundLocalError:
+        yield 6
+
+
+### Py3 feature tests
+
 def print_function(*args):
     """
     >>> print_function(1,2,3)
@@ -29,6 +143,7 @@ def print_function(*args):
     """
     print(*args) # this isn't valid Py2 syntax
 
+
 def exec3_function(cmd):
     """
     >>> exec3_function('a = 1+1')['a']

tests/run/moduletryexcept.pyx

@@ -14,9 +14,9 @@ __doc__ = u"""
 >>> exc[3] is val
 True
 
->>> except_as_deletes
-True
->>> no_match_does_not_delete
+>>> except_as_deletes   # Py2 behaviour
+False
+>>> no_match_does_not_touch_target
 True
 """
 
@@ -81,7 +81,7 @@ except NameError as e:
     pass
 except TypeError:
     pass
-no_match_does_not_delete = (e == 123)
+no_match_does_not_touch_target = (e == 123)
 
 try:
     raise IndexError

tests/run/tryexcept.pyx

@@ -358,19 +358,16 @@ def except_as_no_raise_does_not_touch_target(a):
         i = 2
     return i, b
 
-def except_as_raise_deletes_target(x, a):
+def except_as_raise_does_not_delete_target(x, a):
     """
-    >>> except_as_raise_deletes_target(None, TypeError)
+    >>> except_as_raise_does_not_delete_target(None, TypeError)
     1
-    1
-    >>> except_as_raise_deletes_target(TypeError('test'), TypeError)
-    Traceback (most recent call last):
-    UnboundLocalError: local variable 'b' referenced before assignment
-    >>> except_as_raise_deletes_target(ValueError('test'), TypeError)
+    >>> except_as_raise_does_not_delete_target(TypeError('test'), TypeError)
+    2
+    >>> except_as_raise_does_not_delete_target(ValueError('test'), TypeError)
     Traceback (most recent call last):
     ValueError: test
-    >>> except_as_raise_deletes_target(None, TypeError)
-    1
+    >>> except_as_raise_does_not_delete_target(None, TypeError)
     1
     """
     b = 1
@@ -381,7 +378,12 @@ def except_as_raise_deletes_target(x, a):
     except a as b:
         i = 2
         assert isinstance(b, a)
-    print(b)  # raises UnboundLocalError if except clause was executed
+
+    # exception variable leaks with Py2 except-as semantics
+    if x:
+        assert isinstance(b, a)
+    else:
+        assert b == 1
     return i
 
 def except_as_raise_with_empty_except(x, a):
@@ -397,35 +399,12 @@ def except_as_raise_with_empty_except(x, a):
         if x:
             raise x
         b = 1
-    except a as b:  # previously raised UnboundLocalError
-        pass
-
-def except_as_deletes_target_in_gen(x, a):
-    """
-    >>> list(except_as_deletes_target_in_gen(None, TypeError))
-    [(1, 1), (2, 1), (5, 1)]
-    >>> list(except_as_deletes_target_in_gen(TypeError('test'), TypeError))
-    [(1, 1), 3, 6]
-    >>> list(except_as_deletes_target_in_gen(ValueError('test'), TypeError))
-    [(1, 1), (4, 1), (5, 1)]
-    """
-    b = 1
-    try:
-        i = 1
-        yield (1, b)
-        if x:
-            raise x
-        yield (2, b)
     except a as b:
-        i = 2
+        pass
+    if x:
         assert isinstance(b, a)
-        yield 3
-    except:
-        yield (4, b)
-    try:
-        yield (5, b)
-    except UnboundLocalError:
-        yield 6
+    else:
+        assert b == 1
 
 def complete_except_as_no_raise(a, b):
     """