From 5cd72598feaff3c4bbcc7304a4844768f64a1ee0 Mon Sep 17 00:00:00 2001 From: Eelco Dolstra Date: Wed, 30 Mar 2022 16:31:01 +0200 Subject: 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. --- src/libexpr/eval.cc | 1 + 1 file changed, 1 insertion(+) (limited to 'src/libexpr/eval.cc') diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc index 437c7fc53..b87e06ef5 100644 --- a/src/libexpr/eval.cc +++ b/src/libexpr/eval.cc @@ -436,6 +436,7 @@ EvalState::EvalState( , sBuilder(symbols.create("builder")) , sArgs(symbols.create("args")) , sContentAddressed(symbols.create("__contentAddressed")) + , sImpure(symbols.create("__impure")) , sOutputHash(symbols.create("outputHash")) , sOutputHashAlgo(symbols.create("outputHashAlgo")) , sOutputHashMode(symbols.create("outputHashMode")) -- cgit v1.2.3