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/nix/show-derivation.cc | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'src/nix/show-derivation.cc') diff --git a/src/nix/show-derivation.cc b/src/nix/show-derivation.cc index 0d9655732..fb46b4dbf 100644 --- a/src/nix/show-derivation.cc +++ b/src/nix/show-derivation.cc @@ -77,6 +77,10 @@ struct CmdShowDerivation : InstallablesCommand outputObj.attr("hashAlgo", makeFileIngestionPrefix(dof.method) + printHashType(dof.hashType)); }, [&](const DerivationOutput::Deferred &) {}, + [&](const DerivationOutput::Impure & doi) { + outputObj.attr("hashAlgo", makeFileIngestionPrefix(doi.method) + printHashType(doi.hashType)); + outputObj.attr("impure", true); + }, }, output.raw()); } } -- cgit v1.2.3