Not even when I make sure this configuration is enforced with an environmental variable:
[nix-shell:~]$ NIX_CONFIG='extra-experimental-features = flakes' nix-prefetch fetchurl --urls --expr '[ https://github.com/graalvm/mx/archive/refs/tags/7.25.9.tar.gz ]'
error:
… <borked>
at «none»:0: (source not available)
… in the left operand of the update (//) operator
at /nix/store/2qs4049i0kihlwva9hxk5ywiqk5bigzn-nix-prefetch-0.4.1/lib/nix-prefetch/prelude.nix:3:46:
2|
3| let prelude = with prelude; import ./lib.nix // {
| ^
4| fetcher = if orig.fetcher == null || elem orig.fetcher.type [ "file" "attr" ]
(stack trace truncated; use '--show-trace' to show the full trace)
error: experimental Nix feature 'flakes' is disabled; use '--extra-experimental-features flakes' to override
[nix-shell:~]$ nix-prefetch --version
0.4.1
How to enable the feature? Thanks.