Flakes devShells recently broke with weird error

[NobbZ]

Describe the bug

Trying to enter a devshell for a flake errors weirdly:

error: [json.exception.parse_error.101] parse error at line 55, column 178: syntax error while parsing value - invalid string: ill-formed UTF-8 byte; last read: '" \n    local fn=\"$1\";\n    local fd;\n    local magic;\n    exec {fd}< \"$fn\";\n    read -r -n 4 -u \"$fd\" magic;\n    exec {fd}>&-;\n    if [[ \"$magic\" = '�'

Steps To Reproduce

1. Use nixUnstable with experimental features for flakes and nix-command enabled
2. Use flake.nix from below
3. run nix develop in the flake.

Expected behavior

A dev shell is entered that has gcc

Additional context

This has been observed so far on nixpkgs-unstable, nixos-unstable and master.

Personall I was able to confirm with the following commits (of which I can't say anmore which branch they belong to:

• 2bb5cbf
• cbb9567
• 47eaf67
• 90a37f3

I have to admit though, that we are not sure if this is a problem of nixUnstable or nixpkgs.

What I can say though we had at least 2 versions of nix (nightly as shown below and 2.4pre20210908_3c56f62) in the mix and it broke for both of them.

Metadata

Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

[user@system:~]$ nix shell nixpkgs#nix-info -c nix-info -m
 - system: `"x86_64-linux"`
 - host os: `Linux 5.10.64, NixOS, 21.11 (Porcupine)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.4pre20210915_1ec4efa`
 - channels(root): `"nixos-20.09beta1346.05334ad7852"`
 - channels(demo): `""`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

[holmesmr]

The cause of this seems to be the Flake profile containing a bashFunction for isMachO which contains unescaped bytes which are not valid UTF-8 codepoints: NixOS/nix#4984 (comment)

[winterqt]

The cause of this seems to be the Flake profile containing a bashFunction for isMachO which contains unescaped bytes which are not valid UTF-8 codepoints: NixOS/nix#4984 (comment)

That's correct, yeah.

See #138186 for a temporary fix while the Nix issue is figured out, and NixOS/nix#5262 for details on the underlying Nix issue. (which I now realize is possibly a duplicate of the issue you linked? Not sure.)

[winterqt]

I've made a temporary fix for this issue, which just involves patching Nix (as opposed to patching stdenv and requiring a full rebuild): nix-community/nix-direnv#113 (comment).

[dcarosone]

This reappeared for me recently, after waiting several weeks for the fix to bubble through staging-next, it was finally gone - but now it's back:

$ nix develop
error: [json.exception.parse_error.101] parse error at line 55, column 178: syntax error while parsing value - invalid string: ill-formed UTF-8 byte; last read: '" \n    local fn=\"$1\";\n    local fd;\n    local magic;\n    exec {fd}< \"$fn\";\n    read -r -n 4 -u \"$fd\" magic;\n    exec {fd}>&-;\n    if [[ \"$magic\" = '�'

[winterqt]

@dcarosone What Nixpkgs commit? I cannot reproduce on commit 8e1eab9.

[dcarosone]

It reappeared a couple of days ago, not entirely sure which commit. I had a big update with GNOME 41 that caused a bunch of other issues this morning

21.11pre323079. 2cf9db0

[dcarosone]

Hm. After removing flake.lock it appears to be ok again. Weird.

[winterqt]

@NobbZ I think we should be fine closing this issue by this point.

[NobbZ]

The issue hasn't been mentioned in a while in the discord, thats true.