nix-functional-tests:flakes / flake-in-submodule failed

[minhtrancccp]

Describe the bug

as my machine compiled the latest nix commit while rebuilding nixos, nix-functional-tests failed with the flake-in-submodule test

Steps To Reproduce

1. set up nix flake input and configuration.nix as follows:

# `flake.nix`
inputs.nix.url = "github:nixos/nix";
## then include `inputs` as one of `specialArgs` in `outputs`

# `configuration.nix`
nix.package = inputs.nix.packages.${system}.default;

2. run nix flake update and ensure flake.lock looks similar to the following:

    "nix": {
      "locked": {
        "lastModified": 1736979915,
        "narHash": "sha256-GqR1/TryOjTGBQD3I9oQYekARH5GvlZamSx4VAArVuY=",
        "owner": "nixos",
        "repo": "nix",
        "rev": "0c101679b4c23fdcd27c4f5be42586aa0beff00f",
        "type": "github"
      },
    },

3. run nixos-rebuild test

4. the error is encountered, more details here

Expected behavior

no tests in nix-functional-tests should have failed

Metadata

nix-env (Nix) 2.26.0pre

Additional context

this test seems to have failed since commit e02026a, authored by @edolstra and @Ericson2314. here is the exact error log

Checklist

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

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[edolstra]

I think this was caused by a bad interaction between #12107 (which added a test asserting that libfetcher depends on the cwd, which is very wrong) and #12254 (which resolves git+file: paths early). It seems to have gone away magically thanks to #10089 (since flake.cc no longer calls parseFlakeRef() with a baseDir, so relative git+file: paths are preserved).