Previously, it would not generate any lint messages for nix 2.5.
Moreover, it would cause this error whenever the nix command is
invoked, when paired with a custom `g:ale_command_wrapper`:
Error detected while processing function <SNR>92_NeoVimCallback[29]..<lambda>27[
1]..<SNR>90_ExitCallback[28]..ale_linters#nix#nix#Command:
line 1:
E684: list index out of range: 0
In the (unreleased) Nix 2.4 the error-messages have been reformatted[1].
This patch aims to retain proper `.nix`-support in `ale`, for both
stable Nix (2.3 and older) and unstable Nix (2.4 and newer).
[1] https://github.com/NixOS/nix/pull/3590
Antonio Gurgel
Jeffrey Lau
Maximilian Bosch
w0rp