*From:* users-boun...@lists.ironpython.com
[mailto:users-boun...@lists.ironpython.com] *On Behalf Of *Mike Krell
*Sent:* Monday, May 25, 2009 10:00 AM
*To:* Discussion of IronPython
*Subject:* [IronPython] IPython is breathing but there's a compile()
problem
Now that 2.6B1 has frames support, I've started playing with
IronPython under IPython again. I've managed to get a command prompt
up (some modules are missing, but the only crucial one is codeop,
which I stole from the standard distribution).
However, there's a problem with entering multiline code snippets
interactively. With CPython, this looks like:
In [21]: if 1:
....: if 1:
....:
(The indentation looks wrong without a fixed-width font, but you get
the idea.)
With IronPython, the second "if 1:" line blows up with a syntax error.
This boils down to a difference in the way the compile() builtin works
as used by the codeop module.
I've written this up as a bug at codeplex. Please vote for the bug here:
http://ironpython.codeplex.com/WorkItem/View.aspx?WorkItemId=22692
It would be awesome if we could have a good IronPython + IPython story
before 2.6 is released!
Below are more details about the problem as described in the bug
description.
Mike
--------------------------------------------------------------------------------
bug description at codeplex follows
compile() behaves differently than in CPython in the presence of
incomplete multiline code snippets. Fixing this incompatiblity is
necessary for running IronPython under IPython.
Here is a sample program illustrating the problem. The program is a
modification of the code used in the standard codeop module by IPython
to determine when to provide a continuation prompt for a multiline
snippet.
--------------------------------------------------------------------------------
def testcompile(source, flags):
err = err1 = err2 = None
code = code1 = code2 = None
try:
code = compile(source, "dummy", "single", flags, 1)
except SyntaxError, err:
pass
try:
code1 = compile(source + "\n", "dummy", "single", flags, 1)
except SyntaxError, err1:
pass
try:
code2 = compile(source + "\n\n", "dummy", "single", flags, 1)
except SyntaxError, err2:
pass
print "for source = '%s' and flags = %d" % (source, flags),
if code:
print "Syntax valid"
elif not code1 and repr(err1) == repr(err2):
print "Syntax error!"
print
print "err1:", repr(err1)
print "err2:", repr(err2)
else:
print "Continue on next line"
print
print "err1:", repr(err1)
print "err2:", repr(err2)
print
# 0x200 is PyCF_DONT_IMPLY_DEDENT
testcompile("if 1:", 0x200)
testcompile("if 1:", 0)
testcompile("if 1:\n if 1:", 0x200)
testcompile("if 1:\n if 1:", 0)
--------------------------------------------------------------------------------
Under CPython (2.6.1) the output is:
--------------------------------------------------------------------------------
for source = 'if 1:' and flags = 512 Continue on next line
err1: SyntaxError('unexpected EOF while parsing', ('dummy', 1, 6, 'if
1:\n'))
err2: IndentationError('expected an indented block', ('dummy', 2, 1,
'\n'))
for source = 'if 1:' and flags = 0 Continue on next line
err1: SyntaxError('unexpected EOF while parsing', ('dummy', 1, 6, 'if
1:\n'))
err2: IndentationError('expected an indented block', ('dummy', 2, 1,
'\n'))
for source = 'if 1:
if 1:' and flags = 512 Continue on next line
err1: IndentationError('expected an indented block', ('dummy', 2, 8, '
if 1:\n'))
err2: IndentationError('expected an indented block', ('dummy', 3, 1,
'\n'))
for source = 'if 1:
if 1:' and flags = 0 Continue on next line
err1: IndentationError('expected an indented block', ('dummy', 2, 8, '
if 1:\n'))
err2: IndentationError('expected an indented block', ('dummy', 3, 1,
'\n'))
--------------------------------------------------------------------------------
In all cases the code correctly outputs "Continue on next line" since
both snippets are incomplete but otherwise valid python.
For IronPython 2.6 Beta 1 the output is:
--------------------------------------------------------------------------------
for source = 'if 1:' and flags = 512 Continue on next line
err1: IndentationError("unexpected token '<eof>'", ('dummy', 2, 1, ''))
err2: IndentationError("unexpected token '<eof>'", ('dummy', 3, 1, ''))
for source = 'if 1:' and flags = 0 Continue on next line
err1: IndentationError("unexpected token '<eof>'", ('dummy', 2, 1, ''))
err2: IndentationError("unexpected token '<eof>'", ('dummy', 3, 1, ''))
for source = 'if 1:
if 1:' and flags = 512 Syntax error!
err1: IndentationError("unexpected token '<eof>'", ('dummy', 2, 8, '
if 1:\n'))
err2: IndentationError("unexpected token '<eof>'", ('dummy', 2, 8, '
if 1:\n'))
for source = 'if 1:
if 1:' and flags = 0 Syntax error!
err1: IndentationError("unexpected token '<eof>'", ('dummy', 2, 8, '
if 1:\n'))
err2: IndentationError("unexpected token '<eof>'", ('dummy', 2, 8, '
if 1:\n'))
--------------------------------------------------------------------------------
The second snippet is misinterpreted as being a syntax error instead
of merely incomplete.
This is very similar to the issue described here:
http://www.voidspace.org.uk/python/weblog/arch_d7_2007_09_22.shtml#e834
But it apparently doesn't have to do with PyCF_DONT_IMPLY_DEDENT per
se because the CPython output is the same whether this flag is passed
or not.
------------------------------------------------------------------------
_______________________________________________
Users mailing list
Users@lists.ironpython.com
http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
