--store doesn't work as expected

[zimbatm]

Describe the bug

I don't fully understand the bug yet. When running nix with --store /tmp/foo, things stop working as expected.

Steps To Reproduce

It looks like tools such as builtins.fetchurl return the path to the actual file.

$ nix repl --store /tmp/foo
Welcome to Nix version 3.0pre20200829_f156513. Type :? for help.

nix-repl> builtins.fetchurl "channel:nixos-20.09"
"/tmp/foo/nix/store/nhfagljcxr3idc168k9kfx2w0d5awc5k-nixexprs.tar.xz"

This can lead to issues like this (TODO: include repro):

$ nix develop --store /tmp/foo
error: --- BadStorePath ------------------------------------------------------------------------------------------------------------------- nix
path '/tmp/foo/nix/store/79vpr8pvcf8wlcpjhnsiq2w9nk6467nv-source' is not in the Nix store

Or like this:

$ nix run --store /tmp/foo nixpkgs#hello
error: --- InvalidPath -------------------------------------------------------------------------------------------------------------------- nix
path '/nix/store/5d9nr13b80zlvjwsz9qxx0qq53b8vgzm-nix-3.0pre20200829_f156513' is not valid

Expected behavior

I would expect Nix to bind-mount /tmp/foo/nix to /nix in a user namespace and have all the inherited processed see it the same way.

nix-env --version output
nix-env (Nix) 3.0pre20200829_f156513

[xaverdh]

see #4081

[edolstra]

This works for me:

$ nix run --store /tmp/foo nixpkgs#hello
Hello, world!

[xaverdh]

ah it works from latest master

[xaverdh]

according to my bisect, this was indeed fixed with d9a8619
edit: but that still leaves the issue #4081 linked here; something like it still happens even on recent master

[stale]

I marked this as stale due to inactivity. → More info