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author | Maximilian Bosch <maximilian@mbosch.me> | 2023-09-28 11:05:52 +0200 |
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committer | Maximilian Bosch <maximilian@mbosch.me> | 2023-10-04 18:35:30 +0200 |
commit | 53c5f084151264701e6332f1606bb892bf9c3574 (patch) | |
tree | 0ddce6af6b2909166fdc5d4db93522650f5b505b /pkgs/stdenv/generic | |
parent | 1e41c3352bb8de154f85b85c21bfc911f010b777 (diff) | |
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stdenv: refactor `.attrs.sh` detection
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 Please note that we cannot check for `-e "$NIX_ATTRS_JSON_FILE"` because certain outdated Nix minors (that are still in the range of supported Nix versions in `nixpkgs`) have a bug where `NIX_ATTRS_JSON_FILE` points to the wrong file while building[3]. Also, for compatibility with Nix 2.3 which doesn't provide these environment variables at all we still need to check for the existence of .attrs.json/.attrs.sh here. As soon as we bump nixpkgs' minver to 2.4, this can be dropped. Finally, dropped the check for ATTRS_SH_FILE because that was never relevant. In nix#4770 the ATTRS_SH_FILE variable was introduced[4] and in a review iteration prefixed with NIX_[5]. In other words, these variables were never part of a release and you'd only have this problem if you'd use a Nix from a git revision of my branch from back then. In other words, that's dead code. [1] https://github.com/nixos/nix/pull/4770#issuecomment-834718851 [2] https://github.com/NixOS/nix/pull/9032 [3] https://github.com/NixOS/nix/issues/6736 [4] https://github.com/NixOS/nix/pull/4770/commits/3944a120ec6986c723bf36bfade9b331dd4af68a [5] https://github.com/NixOS/nix/pull/4770/commits/27ce722638eeabb987bc9b4a1234c2818c5bf401
Diffstat (limited to 'pkgs/stdenv/generic')
-rw-r--r-- | pkgs/stdenv/generic/setup.sh | 17 |
1 files changed, 2 insertions, 15 deletions
diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh index ad9857fc9d6..419a66261e6 100644 --- a/pkgs/stdenv/generic/setup.sh +++ b/pkgs/stdenv/generic/setup.sh @@ -16,29 +16,15 @@ if (( "${NIX_DEBUG:-0}" >= 6 )); then set -x fi -if [ -f .attrs.sh ]; then +if [ -f .attrs.sh ] || [[ -n "${NIX_ATTRS_JSON_FILE:-}" ]]; then __structuredAttrs=1 echo "structuredAttrs is enabled" -else - __structuredAttrs= -fi -if [ -n "$__structuredAttrs" ]; then for outputName in "${!outputs[@]}"; do # ex: out=/nix/store/... export "$outputName=${outputs[$outputName]}" done - # Before Nix 2.4, $NIX_ATTRS_*_FILE was named differently: - # https://github.com/NixOS/nix/commit/27ce722 - if [[ -n "${ATTRS_JSON_FILE:-}" ]]; then - export NIX_ATTRS_JSON_FILE="$ATTRS_JSON_FILE" - fi - - if [[ -n "${ATTRS_SH_FILE:-}" ]]; then - export NIX_ATTRS_SH_FILE="$ATTRS_SH_FILE" - fi - # $NIX_ATTRS_JSON_FILE pointed to the wrong location in sandbox # https://github.com/NixOS/nix/issues/6736; please keep around until the # fix reaches *every patch version* that's >= lib/minver.nix @@ -49,6 +35,7 @@ if [ -n "$__structuredAttrs" ]; then export NIX_ATTRS_SH_FILE="$NIX_BUILD_TOP/.attrs.sh" fi else + __structuredAttrs= : "${outputs:=out}" fi |