[bug#41253] [PATCH v3] guix repl: Add script execution.

[Konrad Hinsen <konrad.hinsen@fastmail.net>]

Hi Ludo,

Thanks for your feedback!

> It cannot be used as a shebang, can it?

It can. And that might be worth documenting. Here's an example:

  ===== File foo.scm =========================================
  #!/usr/bin/env -S guix repl
  !#
  (use-modules (ice-9 format))

  (format #t "foo called with arguments: ~s\n"(command-line))
  ===== End of file foo.scm ==================================

  hinsen@guix ~$ ~/foo.scm a b c
  ;;; note: source file /home/hinsen/temp/foo.scm
  ;;;       newer than compiled /home/hinsen/.cache/guile/ccache/3.0-LE-8-4.2/home/hinsen/temp/foo.scm.go
  foo called with arguments: ("/home/hinsen/temp/foo.scm" "a" "b" "c")

The ugly part is that the script needs to be called with '–' as its
first argument if any of the following arguments start with dashes:

  hinsen@guix ~$ ~/foo.scm -- --help
  ;;; note: source file /home/hinsen/temp/foo.scm
  ;;;       newer than compiled /home/hinsen/.cache/guile/ccache/3.0-LE-8-4.2/home/hinsen/temp/foo.scm.go
  foo called with arguments: ("/home/hinsen/temp/foo.scm" "--help")

That could be fixed at the price of a command line interface for "guix
repl" that deviates a bit from Guix conventions. For example,
is there's a file name argument, pass all arguments following it to the
script, eliminating the need for –.

I'll try that in a v4, and also take into account all your remaining
remarks. Just one note on the examples:

>> +@example
>> +$ guix repl -- my-script.scm --input=foo.txt
>> +@end example
>
> I’d remove “$” from the examples.

There are many examples in guix.texi with $, and also many without. Plus
some with # as the command line prompt.

It makes sense to add the command line prompt for examples that also
show output, so I am not sure what the best convention is - but it would
be nice to apply a uniform style everywhere (but NOT as part of
this patch, of course).

Cheers,
  Konrad