`nix develop --command` doesn't work with a flakeref

[colemickens]

Describe the bug

It seems that -c is accepted, but effectively ignored, if the user passes a flakeref at the same time.

Let me show via 3 cases:

Case: -c works with my devShells.x86_64-linux.default (git is coming from the shell):

╭ slynux  ~/code/nixcfg cole-nixcfg-devenv-env 240ms
╰🡒  nix develop --ignore-env -c git --version
warning: Git tree '/home/cole/code/nixcfg' is dirty
git version 2.49.0

Case: it works as expected when I manually enter the devShell, the run a command:

╭ slynux  ~/code/nixcfg shell-ci-env
╰🡒  nix develop .#devenv

╭ slynux  ~/code/nixcfg cole-nixcfg-devenv-env
╰🡒  cargo
Rust's package manager

Case: -c does not work when I use a flakeref to a different devShell:

╭ slynux  ~/code/nixcfg shell-ci-env 2min 37sec 383ms
╰🡒  nix develop .#devenv -c cargo

╭ slynux  ~/code/nixcfg cole-nixcfg-devenv-env 823ms
╰🡒

As you can see, it:

1. does not run my command
2. drops me into the develop environment

Expected behavior

That nix develop -c works similarly with and without a flakeref specified

Metadata

I repro'd this with: 2.29, 2.20.9, 2.24, I'm not sure it has ever worked.

Additional context

Checklist

• checked latest Nix manual (source)
• checked open bug issues and pull requests for possible duplicates

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[colemickens]

Interesting, it seems to be related to specifying the specific devShell output! I can pass a path, and again properly access stuff in the default devShell:

$ nix develop --ignore-env ~/code/nixcfg -c git
usage: git ....