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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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36
src/libcmd/installables.cc
View file

@ -515,6 +515,30 @@ ref<Installable> SourceExprCommand::parseInstallable(
return installables.front();
}
static SingleBuiltPath getBuiltPath(ref<Store> evalStore, ref<Store> store, const SingleDerivedPath & b)
{
return std::visit(
overloaded{
[&](const SingleDerivedPath::Opaque & bo) -> SingleBuiltPath {
return SingleBuiltPath::Opaque { bo.path };
},
[&](const SingleDerivedPath::Built & bfd) -> SingleBuiltPath {
auto drvPath = getBuiltPath(evalStore, store, *bfd.drvPath);
// Resolving this instead of `bfd` will yield the same result, but avoid duplicative work.
SingleDerivedPath::Built truncatedBfd {
.drvPath = makeConstantStorePathRef(drvPath.outPath()),
.output = bfd.output,
};
auto outputPath = resolveDerivedPath(*store, truncatedBfd, &*evalStore);
return SingleBuiltPath::Built {
.drvPath = make_ref<SingleBuiltPath>(std::move(drvPath)),
.output = { bfd.output, outputPath },
};
},
},
b.raw());
}
std::vector<BuiltPathWithResult> Installable::build(
ref<Store> evalStore,
ref<Store> store,
@ -568,7 +592,10 @@ std::vector<std::pair<ref<Installable>, BuiltPathWithResult>> Installable::build
[&](const DerivedPath::Built & bfd) {
auto outputs = resolveDerivedPath(*store, bfd, &*evalStore);
res.push_back({aux.installable, {
.path = BuiltPath::Built { bfd.drvPath, outputs },
.path = BuiltPath::Built {
.drvPath = make_ref<SingleBuiltPath>(getBuiltPath(evalStore, store, *bfd.drvPath)),
.outputs = outputs,
},
.info = aux.info}});
},
[&](const DerivedPath::Opaque & bo) {
@ -597,7 +624,10 @@ std::vector<std::pair<ref<Installable>, BuiltPathWithResult>> Installable::build
for (auto & [outputName, realisation] : buildResult.builtOutputs)
outputs.emplace(outputName, realisation.outPath);
res.push_back({aux.installable, {
.path = BuiltPath::Built { bfd.drvPath, outputs },
.path = BuiltPath::Built {
.drvPath = make_ref<SingleBuiltPath>(getBuiltPath(evalStore, store, *bfd.drvPath)),
.outputs = outputs,
},
.info = aux.info,
.result = buildResult}});
},
@ -691,7 +721,7 @@ StorePathSet Installable::toDerivations(
: throw Error("argument '%s' did not evaluate to a derivation", i->what()));
},
[&](const DerivedPath::Built & bfd) {
drvPaths.insert(bfd.drvPath);
drvPaths.insert(resolveDerivedPath(*store, *bfd.drvPath));
},
}, b.path.raw());