I understood your comment. Maybe we're just doing a prescriptivist/descriptivist thing.
The shebang is a good example of a Unixy affordance with creative applications, and I asked for clarification because I (a descriptivist :) don't see why any specific functionality enabled by this affordance is more or less valid.
> Since POSIX doesn't standardize where env is there is no way to know how to launch env ahead of time.
In a fundamental sense, it's impossible to be certain that code written to run on one system will run on any ~other (including the one it was written on, since it may have mutated it in incompatible ways as soon as execution starts). We can try to trust POSIX, but most distros enable users to mutate the system in ways that even it can't protect us from.
> If there is no way to write a generic shebang you might as well just accept that you will need to change it.
I'm of (at least) two minds about this. It's obviously correct that there's no way to write a generic shebang that will work everywhere. But I think it's also obviously a poor use of human time and attention, at scale, for us to all individually waste time ~localizing every third-party script for every system we ever run it on (perhaps repeatedly, as the system changes). The impossibility of a 100% solution isn't a good reason to shun 90% solutions.
(I say this as someone who develops a tool, https://github.com/abathur/resholve, for ~localizing bash/shell scripts--shebang included. In some sense my ego could benefit from end users needing a tool for this, but the task is inherently fraught on stateful systems and is probably best addressed at the package-manager level.)
> Fair point. I am also biased from PRs also trying to insert flake.nix into projects.
Just as fair. They mean well (and generally just want to make the project easier to distribute or contribute to), but they can be a bit ~deaf to reasonable concerns about adding to the maintenance burden.
> My issue is that nix is doing something nonstandard and it feels like projects are having to accommodate nix's oddities instead of nix being the one to accommodate what already exists.
Also fair, though I hope you'll keep your eyes open for cases where people trying to package a project with Nix are shaking loose portability/reproducibility/underspecification problems that are already latent in the project and are worth fixing even if you ultimately reject the .nix file. (This won't be everything. There are certainly cases where Nix is the only one needing the patch and should do the work to keep up with it.)
Anecdotal, but it's reasonably common to run into projects with hardcoded paths that leave the build/test processes working cleanly on exactly one person's mutable system without anything anywhere saying what that system is or how they bootstrap it. I've seen this include ~snapshotted test outputs that will only pass on the authors system because it's affected by files or even dotfiles that may be in the project directory but not committed, or higher up in the directory tree on the system.
This kind of stuff is just as likely to trip up non-Nix contributors. It may also be a big hurdle to the broader OSS community being able to pick up the torch for them if they get burned out, fall ill, change careers, etc.
(Sometimes maintainers are standoffish about fixing these, especially if they distribute their own binaries or directly push artifacts out to package repositories and so on. They may not understand why we want to build from source or run their test suite or build scripts or build the manual. I'm sympathetic on some level, but I must admit I'm flummoxed when people seem actively incurious about reports that suggest they might have trouble building the project if they lost access to their device).
> Not all instances of it in build scripts are properly rewritten.
Any example? There are definitely asterisks (https://github.com/NixOS/nixpkgs/blob/a4d0fe7270cc03eeb1aba4...), and the default behavior here is one driver for people going out to ask for `/usr/bin/env` (because those can get autopatched). But we do still have the tools to patch them. It isn't the end of the world if you tell us to kick rocks.
> Also there would be work in creating a migration plan to not breaking people who currently rely on its existence.
Yes (though, perhaps ironically, the closest I have to a pitch for Nix is what an incredible lever nix/nixpkgs/NixOS are for experimenting with the feasibility of ideas like this at scale).
