Re: [PATCH] gnu-maintenance: update-package-source: Only update the desired package.

[宋文武]

Andy Wingo <address@hidden> writes:

> On Tue 05 Apr 2016 11:47, address@hidden (Ludovic Courtès) writes:
>
>> Andy Wingo <address@hidden> skribis:
>> [...]
>>>
>>> Sorry to tell you mixed signals, but did you consider Ludovic's
>>> suggestion to use `package-field-location' ?
>>
>> I mentioned it mostly as a possible source of inspiration, but I think
>> it cannot be used as-is here.
>
> Why not?  Using that, you could limit the edit to the field and not the
> whole package.  Anyway, just a thought.
>
>> The trick to determine the boundaries of the ‘package’ form looks
>> reasonable to me.
Yes, I copy the `goto' function from `package-field-location' and
happily notice that after do a `read' it's at the end location of the
object.  Without more thinking :-)


> In that case I think the ideal is something like "edit-expression",
> which takes a source location that starts an expression, uses "read" to
> advance to the end of the expression, then edits the intervening string
> using whatever but verifies that the result can still be read as one
> expression.  Having recorded the absolute byte positions of the start
> and end of the expression, you can then create the output by doing an
> efficient bytevector read of the prologue, then display the string for
> the edited expression, then the bytevector tail.
>
> Again, just a thought!  Feel free to incorporate or not as you like,
> 宋文武 :)
Indeed this is better!  To create the output from bytevector, it's
using `get-bytevector-n' to read and `utf8->string' to write, right?

And I think `edit-expression' could be:
--8<---------------cut here---------------start------------->8---
(define (edit-expression source-properties proc)
  "Edit the object specified by SOURCE-PROPERTIS using PROC, which
should be a procedure that take the original object and returns
a new one."
  ...)
--8<---------------cut here---------------end--------------->8---

I'll try it :-)