structuredAttrs $NIX_ATTRS_JSON_FILE points to the wrong location in sandbox #6736
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i worked around this with https://github.com/NixOS/nixpkgs/blob/d85d5f1723a0fd37577a09620be9527ed368f74b/pkgs/stdenv/generic/setup.sh#L30-L33 but nix develop still has a broken location because NIX_BUILD_TOP is wrong(/build) when setup.sh is sourced easy way to test |
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The bug seems to be in |
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I'll resume that PR later; meanwhile, help is of course appreciated. |
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Fixed in #8053 -- sorry I missed that there was already work happening on this! |
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sternenseemann
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Nix does not (as far it is documented) guarantee that NIX_ATTRS_*_FILE is set, the only [documented] guarantee seems to be: > […] made available to the builder via the file .attrs.json in the > builder’s temporary directory. This guarantee is of course affected by NixOS/nix#6736, so it seems to be prudent to fall back to the Nix 2.3 style ATTRS_*_FILE env vars before defaulting to the expected location in case neither is available. See also: - NixOS#214937 (comment) - NixOS@afef6588e250 [documented]: https://nixos.org/manual/nix/stable/language/advanced-attributes.html#adv-attr-structuredAttrs
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Nix does not (as far it is documented) guarantee that NIX_ATTRS_*_FILE is set, the only [documented] guarantee seems to be: > […] made available to the builder via the file .attrs.json in the > builder’s temporary directory. This guarantee is of course affected by NixOS/nix#6736, so it seems to be prudent to fall back to the Nix 2.3 style ATTRS_*_FILE env vars before defaulting to the expected location in case neither is available. See also: - #214937 (comment) - afef6588e250 [documented]: https://nixos.org/manual/nix/stable/language/advanced-attributes.html#adv-attr-structuredAttrs (cherry picked from commit 1a29857)
Ma27
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Relying on `.attrs.sh` to exist in `$NIX_BUILD_TOP` is problematic
because that's not compatible with how `nix-shell(1)` behaves. It places
`.attrs.{json,sh}` into a temporary directory and makes them accessible via
`$NIX_ATTRS_{SH,JSON}_FILE` in the environment[1]. The sole reason that
`nix-shell(1)` still works with structured-attrs enabled derivations
is that the contents of `.attrs.sh` are sourced into the
shell before sourcing `$stdenv/setup` (if `$stdenv` exists) by `nix-shell`.
However, the assumption that two files called `.attrs.sh` and
`.attrs.json` exist in `$NIX_BUILD_TOP` is wrong in an interactive shell
session and thus an inconsistency between shell debug session and actual
builds which can lead to unexpected problems.
To be precise, we currently have the following problem: an expression
like
with import ./. {};
runCommand "foo" { __structuredAttrs = true; foo.bar = [ 1 2 3 ]; }
''
echo "''${__structuredAttrs@Q}"
touch $out
''
prints `1` in its build-log. However when building interactively in a
`nix-shell`, it doesn't.
Because of that, I'm considering to propose a full deprecation of
`$NIX_BUILD_TOP/.attrs.{json,sh}`. A first step is to only mention the
environment variables, but not the actual paths anymore in Nix's
manual[2]. The second step - this patch - is to fix nixpkgs' stdenv
accordingly.
Please note that we cannot check for `-e "$NIX_ATTRS_JSON_FILE"` because
certain outdated Nix minors (that are still in the range of supported
Nix versions in `nixpkgs`) have a bug where `NIX_ATTRS_JSON_FILE` points
to the wrong file while building[3].
Also, for compatibility with Nix 2.3 which doesn't provide these
environment variables at all we still need to check for the existence of
.attrs.json/.attrs.sh here. As soon as we bump nixpkgs' minver to 2.4,
this can be dropped.
Finally, dropped the check for ATTRS_SH_FILE because that was never
relevant. In nix#4770 the ATTRS_SH_FILE variable was introduced[4] and
in a review iteration prefixed with NIX_[5]. In other words, these
variables were never part of a release and you'd only have this problem
if you'd use a Nix from a git revision of my branch from back then. In
other words, that's dead code.
[1] NixOS/nix#4770 (comment)
[2] NixOS/nix#9032
[3] NixOS/nix#6736
[4] NixOS/nix@3944a12
[5] NixOS/nix@27ce722
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Describe the bug
it points to
/comp-temp/nix-build-bison-3.8.2.drv-2/.attrs.jsonSteps To Reproduce
these commands were run in postPatch of bison on the NixOS/nixpkgs#175649 branch
nix/src/libstore/build/local-derivation-goal.cc
Lines 1093 to 1100 in 6cb4128
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