From bd8571a5c3724ba5917564a5243af173966515c5 Mon Sep 17 00:00:00 2001 From: Taeer Bar-Yam Date: Wed, 23 Nov 2022 12:06:47 -0500 Subject: add explanation and test --- src/nix/why-depends.cc | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'src/nix/why-depends.cc') diff --git a/src/nix/why-depends.cc b/src/nix/why-depends.cc index 285e36722..723017497 100644 --- a/src/nix/why-depends.cc +++ b/src/nix/why-depends.cc @@ -83,6 +83,17 @@ struct CmdWhyDepends : SourceExprCommand { auto package = parseInstallable(store, _package); auto packagePath = Installable::toStorePath(getEvalStore(), store, Realise::Outputs, operateOn, package); + + /* We don't need to build `dependency`. We try to get the store + * path if it's already known, and if not, then it's not a dependency. + * + * Why? If `package` does depends on `dependency`, then getting the + * store path of `package` above necessitated having the store path + * of `dependency`. The contrapositive is, if the store path of + * `dependency` is not already known at this point (i.e. it's a CA + * derivation which hasn't been built), then `package` did not need it + * to build. + */ auto dependency = parseInstallable(store, _dependency); auto derivedDependency = dependency->toDerivedPath(); auto optDependencyPath = std::visit(overloaded { -- cgit v1.2.3