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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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15
src/libexpr/primops.cc
View file

@ -56,7 +56,7 @@ StringMap EvalState::realiseContext(const NixStringContext & context)
.drvPath = b.drvPath,
.outputs = OutputsSpec::Names { b.output },
});
ensureValid(b.drvPath);
ensureValid(b.drvPath->getBaseStorePath());
},
[&](const NixStringContextElem::Opaque & o) {
auto ctxS = store->printStorePath(o.path);
@ -77,7 +77,7 @@ StringMap EvalState::realiseContext(const NixStringContext & context)
if (!evalSettings.enableImportFromDerivation)
debugThrowLastTrace(Error(
"cannot build '%1%' during evaluation because the option 'allow-import-from-derivation' is disabled",
store->printStorePath(drvs.begin()->drvPath)));
drvs.begin()->to_string(*store)));
/* Build/substitute the context. */
std::vector<DerivedPath> buildReqs;
@ -95,7 +95,11 @@ StringMap EvalState::realiseContext(const NixStringContext & context)
/* Get all the output paths corresponding to the placeholders we had */
if (experimentalFeatureSettings.isEnabled(Xp::CaDerivations)) {
res.insert_or_assign(
DownstreamPlaceholder::unknownCaOutput(drv.drvPath, outputName).render(),
DownstreamPlaceholder::fromSingleDerivedPathBuilt(
SingleDerivedPath::Built {
.drvPath = drv.drvPath,
.output = outputName,
}).render(),
store->printStorePath(outputPath)
);
}
@ -1251,7 +1255,10 @@ drvName, Bindings * attrs, Value & v)
}
},
[&](const NixStringContextElem::Built & b) {
drv.inputDrvs[b.drvPath].insert(b.output);
if (auto * p = std::get_if<DerivedPath::Opaque>(&*b.drvPath))
drv.inputDrvs[p->path].insert(b.output);
else
throw UnimplementedError("Dependencies on the outputs of dynamic derivations are not yet supported");
},
[&](const NixStringContextElem::Opaque & o) {
drv.inputSrcs.insert(o.path);