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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
Download patch file Download diff file Expand all files Collapse all files

15
src/libcmd/installable-derived-path.cc
View file

@ -18,14 +18,7 @@ DerivedPathsWithInfo InstallableDerivedPath::toDerivedPaths()
std::optional<StorePath> InstallableDerivedPath::getStorePath()
{
return std::visit(overloaded {
[&](const DerivedPath::Built & bfd) {
return bfd.drvPath;
},
[&](const DerivedPath::Opaque & bo) {
return bo.path;
},
}, derivedPath.raw());
return derivedPath.getBaseStorePath();
}
InstallableDerivedPath InstallableDerivedPath::parse(
@ -42,7 +35,7 @@ InstallableDerivedPath InstallableDerivedPath::parse(
// Remove this prior to stabilizing the new CLI.
if (storePath.isDerivation()) {
auto oldDerivedPath = DerivedPath::Built {
.drvPath = storePath,
.drvPath = makeConstantStorePathRef(storePath),
.outputs = OutputsSpec::All { },
};
warn(
@ -55,8 +48,10 @@ InstallableDerivedPath InstallableDerivedPath::parse(
},
// If the user did use ^, we just do exactly what is written.
[&](const ExtendedOutputsSpec::Explicit & outputSpec) -> DerivedPath {
auto drv = make_ref<SingleDerivedPath>(SingleDerivedPath::parse(*store, prefix));
drvRequireExperiment(*drv);
return DerivedPath::Built {
.drvPath = store->parseStorePath(prefix),
.drvPath = std::move(drv),
.outputs = outputSpec,
};
},