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| author | Eelco Dolstra <edolstra@gmail.com> | 2022-03-30 16:31:01 +0200 |
|---|---|---|
| committer | Eelco Dolstra <edolstra@gmail.com> | 2022-03-31 13:43:20 +0200 |
| commit | 5cd72598feaff3c4bbcc7304a4844768f64a1ee0 (patch) | |
| tree | 4e3f2373bf2a280f19cab7d74101bec108fd8391 /src/libutil | |
| parent | 28309352d991f50c9d8b54a5a0ee99995a1a5297 (diff) | |
Add support for impure derivations
Impure derivations are derivations that can produce a different result
every time they're built. Example:
stdenv.mkDerivation {
name = "impure";
__impure = true; # marks this derivation as impure
outputHashAlgo = "sha256";
outputHashMode = "recursive";
buildCommand = "date > $out";
};
Some important characteristics:
* This requires the 'impure-derivations' experimental feature.
* Impure derivations are not "cached". Thus, running "nix-build" on
the example above multiple times will cause a rebuild every time.
* They are implemented similar to CA derivations, i.e. the output is
moved to a content-addressed path in the store. The difference is
that we don't register a realisation in the Nix database.
* Pure derivations are not allowed to depend on impure derivations. In
the future fixed-output derivations will be allowed to depend on
impure derivations, thus forming an "impurity barrier" in the
dependency graph.
* When sandboxing is enabled, impure derivations can access the
network in the same way as fixed-output derivations. In relaxed
sandboxing mode, they can access the local filesystem.
Diffstat (limited to 'src/libutil')
| -rw-r--r-- | src/libutil/experimental-features.cc | 1 | ||||
| -rw-r--r-- | src/libutil/experimental-features.hh | 1 |
2 files changed, 2 insertions, 0 deletions
diff --git a/src/libutil/experimental-features.cc b/src/libutil/experimental-features.cc index 01f318fa3..e033a4116 100644 --- a/src/libutil/experimental-features.cc +++ b/src/libutil/experimental-features.cc @@ -7,6 +7,7 @@ namespace nix { std::map<ExperimentalFeature, std::string> stringifiedXpFeatures = { { Xp::CaDerivations, "ca-derivations" }, + { Xp::ImpureDerivations, "impure-derivations" }, { Xp::Flakes, "flakes" }, { Xp::NixCommand, "nix-command" }, { Xp::RecursiveNix, "recursive-nix" }, diff --git a/src/libutil/experimental-features.hh b/src/libutil/experimental-features.hh index b5140dcfe..3a254b423 100644 --- a/src/libutil/experimental-features.hh +++ b/src/libutil/experimental-features.hh @@ -16,6 +16,7 @@ namespace nix { enum struct ExperimentalFeature { CaDerivations, + ImpureDerivations, Flakes, NixCommand, RecursiveNix, |