[Python-Dev] #19335 is a codeop, not Idle issue

[Terry Reedy]

I know that many core devs subscribe to the new tracker issues list. If 
you skipped over
http://bugs.python.org/issue19335
because it was (mis) titled as an Idle issue (as I presume most would), 
you might want to reconsider as it is actually a code and in particular, 
a codeop issue. Consider the real interpreter.

C:\Programs\Python33>python
Python 3.3.2 (v3.3.2:d047928ae3f6, May 16 2013, 00:06:53) [MSC v.1600 64 
bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
 >>> def a():
...   def b():
...     nonlocal c
... _ <blinkin>

It waits to see if one enters a blank line (to which it properly 
responds SyntaxError), or continues with something that makes the 
statement syntactically valid.

...   c = 1
...
 >>>

The 'close simulation' in the code module acts differently.

C:\Programs\Python33>python -m code
Python 3.3.2 (v3.3.2:d047928ae3f6, May 16 2013, 00:06:53) [MSC v.1600 64 
bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
 >>> def a():
...  def b():
...   nonlocal c
   File "<string>", line None
SyntaxError: no binding for nonlocal 'c' found

It prematurely acts as if one had entered a fourth, blank line.

InteractiveConsole subclasses InteractiveInterpreter (as does Idle, 
hence the same behavior). II.runsource compiles with 
codeop.CommandCompile, which wraps codeop._maybe_compile, which returns 
None (src incomplete), raises (src complete and bad), or returns code 
(complete and ok) to be executed. For the above code, it re-raises 
SyntaxError instead of returning None. The issue needs someone who can 
find and read the C equivalent used by the real interpreter.

Perhaps the latter was adjusted when nonlocal was introduced, while 
codeop was not.

-- 
Terry Jan Reedy