[Nix-dev] nix-shell (was: Python 3 as default)

[zimbatm]

Point 4 is really the biggest problem for me because the user loses
control. Especially when combined with direnv the user might be surprised
with a big update by just changing directory.

I think that this can be solved using a profile. The user  would load the
profile with nix-shell and use nix-build to switch profiles.

On Tue, 14 Feb 2017, 17:45 Peter Simons, <simons at nospf.cryp.to> wrote:

> Hi Profpatsch,
>
>  >> I hardly ever use nix-shell and I don't want to, to be honest.
>  >
>  > Why is that?
>
> 1. I don't need it. Adding those Haskell/Python/LaTeX/R modules that I
>    need into my global user environment works just fine. I suppose there
>    might be occasions where versions conflict in a way that makes it
>    impossible to add them into the same environment, but I haven't
>    actually encountered that problem yet. Since I don't need more than
>    one shell environment, I don't have to bother will shell.nix files,
>    and I don't have to remember which open shell window is running which
>    environment either.
>
> 2. nix-shells don't nest. And even if they would, many things you'll
>    define inside of a nix-shell won't nest. Thus, you cannot easily
>    compose shell environments, which makes it hard to define accurate
>    environments in a modular and re-usable fashion.
>
> 3. nix-shell interacts poorly with long-running processes. I work on all
>    my projects with Emacs, but I don't want to start Emacs inside of a
>    nix-shell created for one particular project. My Emacs is up and
>    running from the moment I log in and then I don't ever quit it unless
>    I absolutely have to. So having a proper build environment in "some
>    other window" isn't very useful to me. I want to compile by hitting
>    C-c C-c or C-c C-l.
>
> 4. When I update my copy of the Nixpkgs repository, I run "nix-env -u
>    --always" and afterwards everything I'll need to work on all of my
>    projects is available locally in my /nix store. If I see that Nix
>    needs to compile hundreds of packages to do the update, then I may or
>    may not decide to postpone the update. When using nix-shell, I won't
>    know whether it needs to compile for an hour until I've actually run
>    it, i.e. I'll notice that I can't start hacking on some project only
>    after I've decided I want to do that. With one global environment, I
>    have that information for all my projects at the time I decide
>    whether to update or not.
>
> 5. The default nix-shell prompt in bash does not distinguish between
>    "root" and normal users. ;-)
>
> Having said all that, I believe that nix-shell is genuinely useful and I
> do use it every now and then. I wouldn't want to get along without it. I
> just wouldn't want to use it as much as some people apparently do.
>
> Best regards,
> Peter
>
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