From 60b7121d2c6d4322b7c2e8e7acfec7b701b2d3a1 Mon Sep 17 00:00:00 2001 From: John Ericson Date: Sun, 15 Jan 2023 17:39:04 -0500 Subject: Make the Derived Path family of types inductive for dynamic derivations We want to be able to write down `foo.drv^bar.drv^baz`: `foo.drv^bar.drv` is the dynamic derivation (since it is itself a derivation output, `bar.drv` from `foo.drv`). To that end, we create `Single{Derivation,BuiltPath}` types, that are very similar except instead of having multiple outputs (in a set or map), they have a single one. This is for everything to the left of the rightmost `^`. `NixStringContextElem` has an analogous change, and now can reuse `SingleDerivedPath` at the top level. In fact, if we ever get rid of `DrvDeep`, `NixStringContextElem` could be replaced with `SingleDerivedPath` entirely! Important note: some JSON formats have changed. We already can *produce* dynamic derivations, but we can't refer to them directly. Today, we can merely express building or example at the top imperatively over time by building `foo.drv^bar.drv`, and then with a second nix invocation doing `^baz`, but this is not declarative. The ethos of Nix of being able to write down the full plan everything you want to do, and then execute than plan with a single command, and for that we need the new inductive form of these types. Co-authored-by: Robert Hensing Co-authored-by: Valentin Gagarin --- src/libstore/downstream-placeholder.hh | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'src/libstore/downstream-placeholder.hh') diff --git a/src/libstore/downstream-placeholder.hh b/src/libstore/downstream-placeholder.hh index 97f77e6b8..9372dcd58 100644 --- a/src/libstore/downstream-placeholder.hh +++ b/src/libstore/downstream-placeholder.hh @@ -3,6 +3,7 @@ #include "hash.hh" #include "path.hh" +#include "derived-path.hh" namespace nix { @@ -73,6 +74,17 @@ public: const DownstreamPlaceholder & drvPlaceholder, std::string_view outputName, const ExperimentalFeatureSettings & xpSettings = experimentalFeatureSettings); + + /** + * Convenience constructor that handles both cases (unknown + * content-addressed output and unknown derivation), delegating as + * needed to `unknownCaOutput` and `unknownDerivation`. + * + * Recursively builds up a placeholder from a + * `SingleDerivedPath::Built.drvPath` chain. + */ + static DownstreamPlaceholder fromSingleDerivedPathBuilt( + const SingleDerivedPath::Built & built); }; } -- cgit v1.2.3