Re: port-filename and path canonicalization

[Andy Wingo <wingo@pobox.com>]

Hi Ludovic,

On Tue 20 Apr 2010 18:57, ludo@gnu.org (Ludovic Courtès) writes:

>> 2. I think a fluid is still necessary, because a file being
>> compiled can do an `include' or `include-from-path', or even
>> `open-input-file' in a macro, and all these cases you would want the
>> same %file-port-name-canonicalization to take effect.
>
> Indeed, this one is tricky.
>
> I still think it’s application-specific, though.  How about calling the
> fluid, say, %compiler-file-name-canonicalization instead?  :-)

Are you proposing that all file-opening functions check the
%compiler-file-name-canonicalization fluid? Seems better to me for the
name of the fluid to be "close" to the function whose behavior it
changes.

>> 4. The application-level code is nastier if it has to canonicalize,
>> because a relative canonicalization
>
> What do you mean by “relative canonicalization”?
>
> (I have Glibc’s ‘canonicalize_file_name ()’ in mind, which returns an
> absolute path, so I’m confused.)
>
>> cannot in general be passed to open-input-file. For example
>>
>>   (open-input-file "../../module/ice-9/boot-9.scm")
>>
>> is not the same as
>>
>>   (open-input-file "ice-9/boot-9.scm")
>
> Agreed.  :-)

If you build out-of-source, you might end up with

  guile-tools compile -o ice-9/boot-9.go ../../modules/ice-9/boot-9.scm

So the file you open is "../../modules/ice-9/boot-9.scm", but you want
to give it a "relative canonicalization" -- in this case
"ice-9/boot-9.scm" is the canonicalization of
../../modules/ice-9/boot-9.scm, *relative* to "../../modules" (or indeed
to "/home/wingo/src/guile/modules").

>> So you'd have to do a set-port-filename! on the port, mucking up your
>> code -- and how would you decide what to set? In N places you'd have to
>> duplicate fport_canonicalize_filename, and you'd probably have to make
>> scm_i_relativize_path public.
>
> I failed to get the transition at “So”.  :-)
>
> What does scm_i_relativize_path do?  (It lacks a leading comment, hint
> hint.  ;-))

You could try a little harder ;-) Perhaps the paragraph above explains;
you would have to do:

  (define (open-input-file* path)
    (let ((p (open-input-file path)))
      (case (fluid-ref %file-port-name-canonicalization)
        ((absolute)
         (set-port-filename! p (canonicalize-path path)))
        ((relative)
         (set-port-filename! p (relativize-path (canonicalize-path path) %load-path))))
      p))

which is a bit ugly; e.g. include-from-path would need to do this, as
would any third-party equivalent of include-from-path, and even
down to the open-file level. Yuk.

Andy
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