File completion source was replaced with $HOME by unknown reason #18742

I reproduced this on Nushell 0.115.1 (Ubuntu 24.04.4 LTS / WSL2, x86_64). With overlay use inside if true, $env.PWD, /bin/pwd, and ls reflected the new directory, but Tab completion still offered files from the directory where Nu started.

The following worked around it in my tests while keeping the file-existence check. Keep overlay use at the top level of the configuration, and replace the example path with the absolute path to your activate.nu:

const candidate = "/path/to/.venv/bin/activate.nu"
const selected = if ($candidate | path exists) {
    $candidate
} else {
    null
}
overlay use $selected

I tested the same pattern with an existing and a missing file using the minimal overlay. The existing-file case activated the overlay; the missing-file case started without errors and did not activate the test overlay. Tab completion followed both directory changes in each case.

I also tested an environment created with virtualenv 21.7.4 and Python 3.12.3. It selected the virtualenv's Python correctly, and completion followed directory changes while the environment was active.

The important limitation is that this is a parse-time check, not a replacement for arbitrary runtime conditions. const is evaluated during parsing, and overlay use accepts null as a no-op. This does not cover a file created later during execution of the same parsed code.

Separate note about deactivation: in this setup, plain deactivate restored PATH and Python selection but also returned to the startup directory. Completion then agreed with that directory, so this was different from the original completion mismatch.

To deactivate while keeping the current directory, I verified:

overlay hide activate --keep-env [ PWD ]

This disabled the activate overlay and restored PATH, VIRTUAL_ENV, and python3 resolution to their pre-activation values. Both $env.PWD and /bin/pwd stayed in the destination directory, and Tab completion still matched it. The flag is documented for preserving PWD.

I repeated the conditional cases and both deactivation methods in fresh interactive sessions with actual Tab input. I have not tested the original 0.108.0/NixOS environment or established the underlying cause; this is a workaround verified on the setup above.