[Nix-dev] wrapProgram: also pass name as NIX_PROGRAM_NAME

[zimbatm]

Hi Freddy,

Can you expand a bit on why this is a problem? If a program is executed
using python I would expect this to be reflected in the process name. Argv0
would contain a path to python and argv1 the path to the script.

Cheers,
z

On Fri, 19 May 2017, 12:35 Freddy Rietdijk, <freddyrietdijk at fridh.nl> wrote:

> Hi,
>
> When we create a wrapper we use `exec -a` so that the wrapped program uses
> the name of the original program. This isn't respected by all programs,
> e.g. Python ignores this. If I am correct this is the case with all
> interpreters. How do we handle this with other interpreters?
>
> Currently we 'solve' the issue for Python by patching the scripts setting
> `sys.argv[0]` to the original script name, including the full path. This is
> sufficient for scripts that call themselves, however, it is troublesome
> when such a script is wrapped in another derivation, because when the
> script now calls itself, it will call the unwrapped version.
>
> Therefore, I propose we set an environment variable `NIX_PROGRAM_NAME`
> that the scripts check for. To prevent creating yet another `wrapProgram`
> variant I propose we extend `wrapProgram` to always set this variable.
>
> This, however, doesn't solve the issue with nested wrappers yet, because
> if we would use `set`, it would still refer to the name passed by the
> innermost wrapper. Either we try and update wrappers, or, which has my
> preference, we do not use `set` but use `prefix` and make the script pick
> the last item from the list.
>
> What do you think? I like to also refer to the following gist where I've
> been documenting some of the issues and how we can rewrite the Python infra
> to solve those issues.
> https://gist.github.com/FRidh/c3e974e34eac738405af699786b462d5
>
>
> Freddy
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