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

[Eelco Dolstra]

Hi,

On 05/19/2017 01:35 PM, Freddy Rietdijk wrote:

> 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.

The problem with such an environment variable is that it's inherited by child
processes, who might get confused. (E.g. some code might run both in a wrapped
and unwrapped context, so it wouldn't be able to rely on $NIX_PROGRAM_NAME
unambiguously.)

But maybe $NIX_PROGRAM_NAME can be used only in the case where one wrapper
script calls another, so the final wrapper can unset it. However, if we have
wrapper scripts detecting that the wrapped program is also a wrapper script, we
might as well eliminate the execve into the next wrapper (thus preserving the
original argv[0]).

> This, however, doesn't solve the issue with nested wrappers yet

I think in general a) wrappers should be avoided; and b) nested wrappers should
*definitely* be avoided. Wrappers cannot really be avoided for the "delayed
composition" use case (like firefox-wrapper), but in such a case perhaps the
inner wrapper can be eliminated. For example, if the inner wrapper is used to
set $PYTHONPATH, this can be moved into the underlying Python script by setting
sys.path at the start.

-- 
Eelco Dolstra | LogicBlox, Inc. | http://nixos.org/~eelco/