bug#17418: #:select gives access to private variables

bug#17418: #:select gives access to private variables

[Ludovic Courtès]

Consider this module:

--8<---------------cut here---------------start------------->8---
(define-module (t))

(define private #t)
--8<---------------cut here---------------end--------------->8---

And now:

--8<---------------cut here---------------start------------->8---
[ludo@pluto:~/src/guix]$ guile -L .
GNU Guile 2.0.11.20-4338f
Copyright (C) 1995-2014 Free Software Foundation, Inc.

Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
This program is free software, and you are welcome to redistribute it
under certain conditions; type `,show c' for details.

Enter `,help' for help.
scheme@(guile-user)> (use-modules (t))
;;; note: source file ./t.scm
;;;       newer than compiled /home/ludo/.cache/guile/ccache/2.0-LE-8-2.0/home/ludo/src/guix/t.scm.go
;;; note: auto-compilation is enabled, set GUILE_AUTO_COMPILE=0
;;;       or pass the --no-auto-compile argument to disable.
;;; compiling ./t.scm
;;; compiled /home/ludo/.cache/guile/ccache/2.0-LE-8-2.0/home/ludo/src/guix/t.scm.go
scheme@(guile-user)> private
;;; <unknown-location>: warning: possibly unbound variable `private'
ERROR: In procedure #<procedure 1e532a0 ()>:
ERROR: In procedure module-lookup: Unbound variable: private

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
scheme@(guile-user) [1]> 
--8<---------------cut here---------------end--------------->8---

This is as expected.
But adding #:select (private) gives access to ‘private’:

--8<---------------cut here---------------end--------------->8---
[ludo@pluto:~/src/guix]$ guile -L .
GNU Guile 2.0.11.20-4338f
Copyright (C) 1995-2014 Free Software Foundation, Inc.

Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
This program is free software, and you are welcome to redistribute it
under certain conditions; type `,show c' for details.

Enter `,help' for help.
scheme@(guile-user)> (use-modules ((t) #:select (private)))
scheme@(guile-user)> private
$1 = #t
--8<---------------cut here---------------end--------------->8---

Ludo’.

bug#17418: #:select gives access to private variables

[Mark H Weaver]

ludo@gnu.org (Ludovic Courtès) writes:

> Consider this module:
>
> (define-module (t))
>
> (define private #t)
>
> And now:
>
> [ludo@pluto:~/src/guix]$ guile -L .
> GNU Guile 2.0.11.20-4338f
> Copyright (C) 1995-2014 Free Software Foundation, Inc.
>
> Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
> This program is free software, and you are welcome to redistribute it
> under certain conditions; type `,show c' for details.
>
> Enter `,help' for help.
> scheme@(guile-user)> (use-modules (t))
> ;;; note: source file ./t.scm
> ;;;       newer than compiled /home/ludo/.cache/guile/ccache/2.0-LE-8-2.0/home/ludo/src/guix/t.scm.go
> ;;; note: auto-compilation is enabled, set GUILE_AUTO_COMPILE=0
> ;;;       or pass the --no-auto-compile argument to disable.
> ;;; compiling ./t.scm
> ;;; compiled /home/ludo/.cache/guile/ccache/2.0-LE-8-2.0/home/ludo/src/guix/t.scm.go
> scheme@(guile-user)> private
> ;;; <unknown-location>: warning: possibly unbound variable `private'
> ERROR: In procedure #<procedure 1e532a0 ()>:
> ERROR: In procedure module-lookup: Unbound variable: private
>
> Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
> scheme@(guile-user) [1]> 
>
> This is as expected.
> But adding #:select (private) gives access to ‘private’:
>
> [ludo@pluto:~/src/guix]$ guile -L .
> GNU Guile 2.0.11.20-4338f
> Copyright (C) 1995-2014 Free Software Foundation, Inc.
>
> Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
> This program is free software, and you are welcome to redistribute it
> under certain conditions; type `,show c' for details.
>
> Enter `,help' for help.
> scheme@(guile-user)> (use-modules ((t) #:select (private)))
> scheme@(guile-user)> private
> $1 = #t

I agree that this is arguably a bug, but there exists code that depends
on this behavior.  One example is system/repl/coop-server.scm, which
needs access to some private bindings from system/repl/server.scm and
system/repl/repl.scm.  I confess that I even suggested it, because the
alternatives were unpleasant.

Perhaps we should consider making #:select issue a warning when it
imports private bindings, and also adding a mechanism to import private
bindings without a warning.

What do you think?

    Mark

bug#17418: #:select gives access to private variables

[Ludovic Courtès]

Hi, Mark!

Mark H Weaver <mhw@netris.org> skribis:

> Perhaps we should consider making #:select issue a warning when it
> imports private bindings,

Yes, sounds like a good idea.

> and also adding a mechanism to import private bindings without a
> warning.

I’m unsure about this.  Normally we don’t want to allow that, because
that defeats the purpose of modules.  OTOH, in practice we occasionally
need this ability; I typically use @@ for that, but it’s not as nice as
a real import.

Any idea what other schemes do?

Ludo’.

bug#17418: #:select gives access to private variables

[Mark H Weaver]

ludo@gnu.org (Ludovic Courtès) writes:

> Mark H Weaver <mhw@netris.org> skribis:
>
>> Perhaps we should consider making #:select issue a warning when it
>> imports private bindings,
>
> Yes, sounds like a good idea.

Sounds good.  Specifically, I guess we should deprecate this way of
using #:select.

If you do this, can you adjust system/repl/coop-server.scm to avoid it?
It imports the following private bindings:

  start-repl* run-server* add-open-socket! close-socket!

>> and also adding a mechanism to import private bindings without a
>> warning.
>
> I’m unsure about this.  Normally we don’t want to allow that, because
> that defeats the purpose of modules.

Fair enough.  Having mulled it over, I tend to agree that we should not
try to make this more convenient.

> OTOH, in practice we occasionally need this ability; I typically use
> @@ for that, but it’s not as nice as a real import.

I think asking people to use @@ is reasonable here.

    Thanks,
      Mark

bug#17418: #:select gives access to private variables

[Mark H Weaver]

Mark H Weaver <mhw@netris.org> writes:
> Sounds good.  Specifically, I guess we should deprecate this way of
> using #:select.
>
> If you do this, can you adjust system/repl/coop-server.scm to avoid it?
> It imports the following private bindings:
>
>   start-repl* run-server* add-open-socket! close-socket!

Also: prompting-meta-read

     Mark

bug#17418: #:select gives access to private variables

[Andy Wingo]

On Wed 04 Jun 2014 01:11, Mark H Weaver <mhw@netris.org> writes:

> Mark H Weaver <mhw@netris.org> writes:
>> Sounds good.  Specifically, I guess we should deprecate this way of
>> using #:select.
>>
>> If you do this, can you adjust system/repl/coop-server.scm to avoid it?
>> It imports the following private bindings:
>>
>>   start-repl* run-server* add-open-socket! close-socket!
>
> Also: prompting-meta-read

Fixed in master.

Andy

bug#17418: #:select gives access to private variables

[Ludovic Courtès]

Andy Wingo <wingo@pobox.com> skribis:

> On Wed 04 Jun 2014 01:11, Mark H Weaver <mhw@netris.org> writes:
>
>> Mark H Weaver <mhw@netris.org> writes:
>>> Sounds good.  Specifically, I guess we should deprecate this way of
>>> using #:select.
>>>
>>> If you do this, can you adjust system/repl/coop-server.scm to avoid it?
>>> It imports the following private bindings:
>>>
>>>   start-repl* run-server* add-open-socket! close-socket!
>>
>> Also: prompting-meta-read
>
> Fixed in master.

I would not close the bug if it remains in 2.0.x.  Thoughts?

Ludo’.

bug#17418: #:select gives access to private variables

[Andy Wingo]

On Tue 21 Jun 2016 16:52, ludo@gnu.org (Ludovic Courtès) writes:

> Andy Wingo <wingo@pobox.com> skribis:
>
>> On Wed 04 Jun 2014 01:11, Mark H Weaver <mhw@netris.org> writes:
>>
>>> Mark H Weaver <mhw@netris.org> writes:
>>>> Sounds good.  Specifically, I guess we should deprecate this way of
>>>> using #:select.
>>>>
>>>> If you do this, can you adjust system/repl/coop-server.scm to avoid it?
>>>> It imports the following private bindings:
>>>>
>>>>   start-repl* run-server* add-open-socket! close-socket!
>>>
>>> Also: prompting-meta-read
>>
>> Fixed in master.
>
> I would not close the bug if it remains in 2.0.x.  Thoughts?

I think we can't break 2.0 in this regard; it's technically
incompatible.  We could print a better deprecation warning but in this
case I think I did the right thing.  WDYT?

A

bug#17418: #:select gives access to private variables

[Ludovic Courtès]

Andy Wingo <wingo@pobox.com> skribis:

> On Tue 21 Jun 2016 16:52, ludo@gnu.org (Ludovic Courtès) writes:
>
>> Andy Wingo <wingo@pobox.com> skribis:
>>
>>> On Wed 04 Jun 2014 01:11, Mark H Weaver <mhw@netris.org> writes:
>>>
>>>> Mark H Weaver <mhw@netris.org> writes:
>>>>> Sounds good.  Specifically, I guess we should deprecate this way of
>>>>> using #:select.
>>>>>
>>>>> If you do this, can you adjust system/repl/coop-server.scm to avoid it?
>>>>> It imports the following private bindings:
>>>>>
>>>>>   start-repl* run-server* add-open-socket! close-socket!
>>>>
>>>> Also: prompting-meta-read
>>>
>>> Fixed in master.
>>
>> I would not close the bug if it remains in 2.0.x.  Thoughts?
>
> I think we can't break 2.0 in this regard; it's technically
> incompatible.  We could print a better deprecation warning but in this
> case I think I did the right thing.  WDYT?

Yeah, you’re probably right; it would suddenly lead to unbound
variables, whether or not people realized they were relying on
“unspecified” behavior.

I withdraw my remark!

Ludo’.