Hash prefetching commands (sometimes?) need the flakes experimental feature

[therealpxc]

Try running

nurl --hash -f fetchPypi https://pypi.org/project/semgrep 1.32.0 -A format wheel -A dist cp37.cp38.cp39.cp310.cp311.py37.py38.py39.py310.py311 -A python cp37.cp38.cp39.cp310.cp311.py37.py38.py39.py310.py311 -A platform macosx_11_0_arm64

on Nix 2.15 or 2.16.1, and you'll see a message saying that the flakes feature needs to be enabled, like this:

error:
       … while calling the 'import' builtin

         at «string»:1:2:

            1| (import(<nixpkgs>){}).fetchPypi{pname="semgrep";version="1.32.0";hash="sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";format="wheel";dist="cp37.cp38.cp39.cp310.cp311.py37.py38.py39.py310.py311";python="cp37.cp38.cp39.cp310.cp311.py37.py38.py39.py310.py311";platform="macosx_11_0_arm64";}
             |  ^

       … while calling the 'findFile' builtin

         at «string»:1:9:

            1| (import(<nixpkgs>){}).fetchPypi{pname="semgrep";version="1.32.0";hash="sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";format="wheel";dist="cp37.cp38.cp39.cp310.cp311.py37.py38.py39.py310.py311";python="cp37.cp38.cp39.cp310.cp311.py37.py38.py39.py310.py311";platform="macosx_11_0_arm64";}
             |         ^

       error: experimental Nix feature 'flakes' is disabled; use '--extra-experimental-features flakes' to override
       ```
       
Since I already have flakes enabled, changing the `nix-build` invocation to `--extra-experimental-features` instead of `--experimental-features` fixes the problem for me.

[figsoda]

not sure why <nixpkgs> would use flakes, but c5a8c3c should fix the issue for now

[therealpxc]

Yeah, seems like this might really be an upstream bug. I'm glad that workaround was agreeable and thankful for its speedy addition!

[figsoda]

released v0.3.13, feel free to reopen this if this is not an upstream bug