Re: ancient convert rules

[Jonas Hahnfeld]

Am Sonntag, den 30.08.2020, 22:37 +0200 schrieb Jonas Hahnfeld:
> Am Sonntag, den 30.08.2020, 22:12 +0200 schrieb Jean Abou Samra:
> > > What if we kept a legacy convert.ly that went from the origin to, say
> > > 2.12.0 that was still Python 2 based?  And then had the new, Python 
> > > 3-based
> > > convert.ly start from 2.12.0?
> > > 
> > > This would provide a way for anybody who needed to get old source code up
> > > to the current standard to do so, and would eliminate the burden of
> > > converting the whole file to Python 3.
> > > 
> > > Thanks,
> > > 
> > > Carl
> > 
> > Maybe the solution is just to mention somewhere in the documentation of
> > convert-ly that if the user wants to upgrade from older that 2.12 or 
> > whatever, they can use the convert-ly from LilyPond 2.18?
> 
> If we want to maintain all old rules, I think it's better to have them
> stay one script. Python 2 will hopefully go away at some point, if the
> rules are needed they should be fixed.
> 
> 
> > > I definitely overlooked how often there are*too many*  backslashes in
> > > the code. So there are a lot more changes requried than what is in merge
> > > request 363:
> > 
> > Also, you fixed invalid escape sequences -- thanks for that! --, but 
> > pylint can't
> > spot cases where there aren't many actual backslash characters in the 
> > resulting string
> > to escape backslashes in the regular expression (the second level of 
> > escaping), like in Jonas'
> > original example. This is why it seems all ancient rules would require a 
> > decent
> > amount of work to be made to work with Python 3, if I understand correctly.
> 
> I think it's not that bad, I went through 24 instances of this.
> What's giving me more headaches right now is the rule for 2.5.13 to
> remove \encoding. As far as I understand, it tries to re-encode the
> whole file which won't work easily because the content is already read
> in UTF-8 mode. As far as I understand, \encoding "latin1" basically
> meant binary mode in LilyPond? I guess I have to look this up in git.

I think I found a solution that works equally well as it did when
running convert-ly with Python 2. Please see the second commit of 
https://gitlab.com/lilypond/lilypond/-/merge_requests/365 for what I
tested.

Jonas

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