From: Michael Albinus <michael.albinus@gmx.de>
To: Augusto Stoffel <arstoffel@gmail.com>
Cc: Stefan Monnier <monnier@iro.umontreal.ca>, emacs-devel@gnu.org
Subject: Re: Buffer-local process environments
Date: Fri, 30 Apr 2021 17:51:37 +0200 [thread overview]
Message-ID: <87a6pfepo6.fsf@gmx.de> (raw)
In-Reply-To: <87eeerby1n.fsf@gmail.com> (Augusto Stoffel's message of "Fri, 30 Apr 2021 17:19:00 +0200")
Augusto Stoffel <arstoffel@gmail.com> writes:
>> Because there's a lot of functions out there, which work for the local
>> host, and should work also for remote hosts. See for example
>> vc-git-grep, which has
>>
>> (let ((default-directory dir)
>> (compilation-environment (cons "PAGER=" compilation-environment)))
>>
>> compilation-environment will be propagated to process-environment later
>> on. And the setting for PAGER is needed for both local and remote
>> instances of vc-git-grep. There's no special code in vc-git-grep for the
>> remote case.
>
> Some observations:
>
> 1. In this case, one could call "git --no-pager" instead of relying on
> an env var.
>
> 2. PAGER is overridden by `tramp-remote-process-environment' anyway,
> right? And unlike something of the likes of PYTHONPATH, I see no
> reason to customize PAGER.
>
> 3. If Tramp checked for the buffer-local value of process-environment
> instead of the default value, then the patch for compile.el I
> attached yesterday wouldn't break for remote directories, and the
> let-binding trick in your example would still work.
Please, it is just an example. And Tramp settings, like PAGER, have been
added later on.
A simple rgrep for "(process-environment" over Emacs' lisp directory
shows you several other hits, some of them are good for this discussion:
./vc/vc-bzr.el97: (let ((process-environment (cons (format "BZR_LOG=%s" null-device)
./vc/vc-hg.el1432: (process-environment (cons "HGPLAIN=1" process-environment))
./vc/vc-hg.el1507: (process-environment (cons "HGPLAIN=1" process-environment))
./vc/vc-hg.el1522: (let ((process-environment (cons "HGPLAIN=1" process-environment))
./vc/vc-dispatcher.el328: (process-environment (cons "LC_MESSAGES=C" process-environment))
This list is not comprehensive, of course. And again, I have no idea
what is used in the wild.
> So I wonder:
>
> A. Are there more compelling examples showing that Lisp code needs
> fine-grained control over variables being exported to a remote host?
>
> B. There is probably a small list of variables that should be preserved
> across machines, while there is an unbounded quantity of variables
> that probably only make sense machine-locally (e.g., any variable
> holding directory names).
>
> In view of 3., one could introduce the convention that the buffer-local
> value of `process-environment' is for "project-local" variables, and the
> let-bound value is for variables that make sense even on remote machines.
>
> I'm not sure this is a good proposal, though. It's a subtle rule, and
> it could be quite brittle and hard to use.
Honestly, the hack we have now is already annoying, at least to me. I
would prefer to have something more solid to apply.
> An alternative proposal is to introduce a variable
> `remote-exported-variables', which anyone could set or let-bind or even
> override on a connection-local basis. The value of any variable whose
> name appears in this list would be passed though a remote connection.
> This proposal would make a lot of sense if assumption B. is true.
There is already tramp-remote-process-environment, for many years. Not
much appreciated by package authors.
Best regards, Michael.
next prev parent reply other threads:[~2021-04-30 15:51 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-29 10:56 Buffer-local process environments Augusto Stoffel
2021-04-29 12:30 ` Eli Zaretskii
2021-04-29 12:40 ` Augusto Stoffel
2021-04-29 12:52 ` Eli Zaretskii
2021-04-29 13:06 ` Augusto Stoffel
2021-04-29 14:02 ` Stefan Monnier
2021-04-29 17:26 ` Augusto Stoffel
2021-04-29 17:34 ` Michael Albinus
2021-04-30 7:29 ` Augusto Stoffel
2021-04-30 7:48 ` Michael Albinus
2021-04-30 15:19 ` Augusto Stoffel
2021-04-30 15:51 ` Michael Albinus [this message]
2021-05-02 6:13 ` Augusto Stoffel
2021-05-08 17:51 ` Michael Albinus
2021-05-09 5:06 ` Augusto Stoffel
2021-05-09 16:38 ` Michael Albinus
2021-08-28 12:28 ` [PATCH] " Augusto Stoffel
2021-08-28 12:37 ` Eli Zaretskii
2021-08-28 12:55 ` Augusto Stoffel
2021-09-01 10:42 ` Stephen Leake
2021-09-01 10:56 ` Augusto Stoffel
2021-09-01 22:38 ` Stephen Leake
2021-09-02 7:14 ` Augusto Stoffel
2021-09-06 15:17 ` Stephen Leake
2021-08-28 14:06 ` Arthur Miller
2021-08-28 14:33 ` Eli Zaretskii
2021-08-28 15:27 ` Arthur Miller
2021-08-28 15:38 ` Eli Zaretskii
2021-08-28 16:48 ` Arthur Miller
2021-08-28 15:39 ` Augusto Stoffel
2021-08-28 16:43 ` Arthur Miller
2021-08-28 12:47 ` Michael Albinus
2021-08-28 12:59 ` Augusto Stoffel
2021-08-28 13:18 ` Michael Albinus
2021-08-28 13:54 ` Augusto Stoffel
2021-08-28 14:05 ` Stefan Monnier
2021-08-28 15:19 ` Augusto Stoffel
2021-04-30 15:32 ` Augusto Stoffel
2021-04-30 15:55 ` Michael Albinus
2021-04-29 15:37 ` Michael Albinus
2021-04-29 17:31 ` Augusto Stoffel
2021-04-29 17:44 ` Michael Albinus
2021-04-30 7:00 ` Augusto Stoffel
2021-04-30 7:25 ` Michael Albinus
2021-05-02 13:45 ` Stephen Leake
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