nix-super/src/libstore/path-with-outputs.hh
John Ericson 60b7121d2c 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 `<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>
2023-08-10 00:08:32 -04:00

47 lines
1.3 KiB
C++

#pragma once
///@file
#include "path.hh"
#include "derived-path.hh"
namespace nix {
/**
* This is a deprecated old type just for use by the old CLI, and older
* versions of the RPC protocols. In new code don't use it; you want
* `DerivedPath` instead.
*
* `DerivedPath` is better because it handles more cases, and does so more
* explicitly without devious punning tricks.
*/
struct StorePathWithOutputs
{
StorePath path;
std::set<std::string> outputs;
std::string to_string(const Store & store) const;
DerivedPath toDerivedPath() const;
typedef std::variant<StorePathWithOutputs, StorePath, std::monostate> ParseResult;
static StorePathWithOutputs::ParseResult tryFromDerivedPath(const DerivedPath &);
};
std::vector<DerivedPath> toDerivedPaths(const std::vector<StorePathWithOutputs>);
std::pair<std::string_view, StringSet> parsePathWithOutputs(std::string_view s);
class Store;
/**
* Split a string specifying a derivation and a set of outputs
* (/nix/store/hash-foo!out1,out2,...) into the derivation path
* and the outputs.
*/
StorePathWithOutputs parsePathWithOutputs(const Store & store, std::string_view pathWithOutputs);
StorePathWithOutputs followLinksToStorePathWithOutputs(const Store & store, std::string_view pathWithOutputs);
}