[Python-Dev] Tweaking AST lineno and col_offset

Brett Cannon brett at python.org
Fri Aug 14 23:57:02 CEST 2009

On Fri, Aug 14, 2009 at 09:16, Benjamin Peterson <benjamin at python.org>wrote:

> 2009/8/14 Frank Wierzbicki <fwierzbicki at gmail.com>:
> > Hi all,
> >
> > Off and on I have been directly comparing Jython's AST with Python's
> > AST and generally working towards making them as close to identical as
> > possible.  There are a couple of places where I haven't "fixed" Jython
> > because it looks to me like Jython has slightly better offsets.  One
> > example:
> >
> > for a,b in c:
> >    pass
> >
> > The Tuple node "a,b" ends up with a col_offset of 0 (the position of
> > the "for") where Jython has the col_offset as 4 (the position of "a").
> >  Jython's result is more consistent with other Tuple node col_offset
> > results.
> >
> > I have a local patch that changes the CPython col_offset to match
> > Jython's, but before I submit a patch I thought I'd ask here if there
> > is support for this sort of change and if I should continue to find
> > col_offset and lineno results that look fishy to me, or should I just
> > change Jython's results to match (one way or another, things will be
> > much easier for me to test if they match).
> Yes, please submit it.
> >
> > Also, would this be a change that would be considered a backwards
> > incompatibility?  In other words, would patches like this be allowed
> > in 2.6/3.1 or only in 2.7/3.2.
> While I don't see a problem in backporting it to maintence branches, I
> would personally only apply it to the current development branches. It
> doesn't seem to fix a "bug", just make a nice improvement.

I like the improvement, but I disagree it should be considered for
backporting as it changes semantics for something that could be considered a
bug, but that feels like a stretch.

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