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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.
125 lines
4.1 KiB
C++
125 lines
4.1 KiB
C++
// FIXME: integrate this with nix path-info?
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// FIXME: rename to 'nix store show-derivation' or 'nix debug show-derivation'?
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#include "command.hh"
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#include "common-args.hh"
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#include "store-api.hh"
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#include "archive.hh"
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#include "json.hh"
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#include "derivations.hh"
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using namespace nix;
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struct CmdShowDerivation : InstallablesCommand
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{
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bool recursive = false;
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CmdShowDerivation()
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{
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addFlag({
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.longName = "recursive",
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.shortName = 'r',
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.description = "Include the dependencies of the specified derivations.",
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.handler = {&recursive, true}
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});
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}
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std::string description() override
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{
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return "show the contents of a store derivation";
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}
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std::string doc() override
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{
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return
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#include "show-derivation.md"
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;
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}
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Category category() override { return catUtility; }
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void run(ref<Store> store) override
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{
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auto drvPaths = Installable::toDerivations(store, installables, true);
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if (recursive) {
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StorePathSet closure;
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store->computeFSClosure(drvPaths, closure);
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drvPaths = std::move(closure);
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}
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{
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JSONObject jsonRoot(std::cout, true);
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for (auto & drvPath : drvPaths) {
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if (!drvPath.isDerivation()) continue;
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auto drvObj(jsonRoot.object(store->printStorePath(drvPath)));
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auto drv = store->readDerivation(drvPath);
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{
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auto outputsObj(drvObj.object("outputs"));
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for (auto & [_outputName, output] : drv.outputs) {
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auto & outputName = _outputName; // work around clang bug
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auto outputObj { outputsObj.object(outputName) };
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std::visit(overloaded {
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[&](const DerivationOutput::InputAddressed & doi) {
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outputObj.attr("path", store->printStorePath(doi.path));
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},
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[&](const DerivationOutput::CAFixed & dof) {
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outputObj.attr("path", store->printStorePath(dof.path(*store, drv.name, outputName)));
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outputObj.attr("hashAlgo", dof.hash.printMethodAlgo());
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outputObj.attr("hash", dof.hash.hash.to_string(Base16, false));
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},
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[&](const DerivationOutput::CAFloating & dof) {
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outputObj.attr("hashAlgo", makeFileIngestionPrefix(dof.method) + printHashType(dof.hashType));
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},
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[&](const DerivationOutput::Deferred &) {},
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[&](const DerivationOutput::Impure & doi) {
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outputObj.attr("hashAlgo", makeFileIngestionPrefix(doi.method) + printHashType(doi.hashType));
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outputObj.attr("impure", true);
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},
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}, output.raw());
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}
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}
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{
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auto inputsList(drvObj.list("inputSrcs"));
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for (auto & input : drv.inputSrcs)
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inputsList.elem(store->printStorePath(input));
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}
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{
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auto inputDrvsObj(drvObj.object("inputDrvs"));
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for (auto & input : drv.inputDrvs) {
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auto inputList(inputDrvsObj.list(store->printStorePath(input.first)));
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for (auto & outputId : input.second)
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inputList.elem(outputId);
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}
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}
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drvObj.attr("system", drv.platform);
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drvObj.attr("builder", drv.builder);
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{
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auto argsList(drvObj.list("args"));
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for (auto & arg : drv.args)
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argsList.elem(arg);
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}
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{
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auto envObj(drvObj.object("env"));
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for (auto & var : drv.env)
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envObj.attr(var.first, var.second);
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}
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}
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}
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std::cout << "\n";
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}
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};
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static auto rCmdShowDerivation = registerCommand<CmdShowDerivation>("show-derivation");
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