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/libexpr/eval.hh | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'src/libexpr/eval.hh') diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh index 29d0f05a1..0268a2a12 100644 --- a/src/libexpr/eval.hh +++ b/src/libexpr/eval.hh @@ -22,7 +22,7 @@ namespace nix { class Store; class EvalState; class StorePath; -struct DerivedPath; +struct SingleDerivedPath; enum RepairFlag : bool; @@ -532,12 +532,12 @@ public: StorePath coerceToStorePath(const PosIdx pos, Value & v, NixStringContext & context, std::string_view errorCtx); /** - * Part of `coerceToDerivedPath()` without any store IO which is exposed for unit testing only. + * Part of `coerceToSingleDerivedPath()` without any store IO which is exposed for unit testing only. */ - std::pair coerceToDerivedPathUnchecked(const PosIdx pos, Value & v, std::string_view errorCtx); + std::pair coerceToSingleDerivedPathUnchecked(const PosIdx pos, Value & v, std::string_view errorCtx); /** - * Coerce to `DerivedPath`. + * Coerce to `SingleDerivedPath`. * * Must be a string which is either a literal store path or a * "placeholder (see `DownstreamPlaceholder`). @@ -551,7 +551,7 @@ public: * source of truth, and ultimately tells us what we want, and then * we ensure the string corresponds to it. */ - DerivedPath coerceToDerivedPath(const PosIdx pos, Value & v, std::string_view errorCtx); + SingleDerivedPath coerceToSingleDerivedPath(const PosIdx pos, Value & v, std::string_view errorCtx); public: -- cgit v1.2.3