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Make the Derived Path family of types inductive for dynamic derivations

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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 `<result-from-first>^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 <roberth@users.noreply.github.com>
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
This commit is contained in:
John Ericson 2023-01-15 17:39:04 -05:00
parent d00fe5f225
commit 60b7121d2c
48 changed files with 1136 additions and 267 deletions
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50
src/libcmd/built-path.hh
View file

@ -3,19 +3,60 @@
namespace nix {
struct SingleBuiltPath;
struct SingleBuiltPathBuilt {
ref<SingleBuiltPath> drvPath;
std::pair<std::string, StorePath> output;
std::string to_string(const Store & store) const;
static SingleBuiltPathBuilt parse(const Store & store, std::string_view, std::string_view);
nlohmann::json toJSON(const Store & store) const;
DECLARE_CMP(SingleBuiltPathBuilt);
};
using _SingleBuiltPathRaw = std::variant<
DerivedPathOpaque,
SingleBuiltPathBuilt
>;
struct SingleBuiltPath : _SingleBuiltPathRaw {
using Raw = _SingleBuiltPathRaw;
using Raw::Raw;
using Opaque = DerivedPathOpaque;
using Built = SingleBuiltPathBuilt;
inline const Raw & raw() const {
return static_cast<const Raw &>(*this);
}
StorePath outPath() const;
static SingleBuiltPath parse(const Store & store, std::string_view);
nlohmann::json toJSON(const Store & store) const;
};
static inline ref<SingleBuiltPath> staticDrv(StorePath drvPath)
{
return make_ref<SingleBuiltPath>(SingleBuiltPath::Opaque { drvPath });
}
/**
* A built derived path with hints in the form of optional concrete output paths.
*
* See 'BuiltPath' for more an explanation.
*/
struct BuiltPathBuilt {
StorePath drvPath;
ref<SingleBuiltPath> drvPath;
std::map<std::string, StorePath> outputs;
nlohmann::json toJSON(ref<Store> store) const;
static BuiltPathBuilt parse(const Store & store, std::string_view);
std::string to_string(const Store & store) const;
static BuiltPathBuilt parse(const Store & store, std::string_view, std::string_view);
nlohmann::json toJSON(const Store & store) const;
GENERATE_CMP(BuiltPathBuilt, me->drvPath, me->outputs);
DECLARE_CMP(BuiltPathBuilt);
};
using _BuiltPathRaw = std::variant<
@ -41,6 +82,7 @@ struct BuiltPath : _BuiltPathRaw {
StorePathSet outPaths() const;
RealisedPath::Set toRealisedPaths(Store & store) const;
nlohmann::json toJSON(const Store & store) const;
};
typedef std::vector<BuiltPath> BuiltPaths;