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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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59
src/libexpr/eval.cc
View file

@ -1042,7 +1042,7 @@ void EvalState::mkOutputString(
: DownstreamPlaceholder::unknownCaOutput(drvPath, outputName, xpSettings).render(),
NixStringContext {
NixStringContextElem::Built {
.drvPath = drvPath,
.drvPath = makeConstantStorePathRef(drvPath),
.output = outputName,
}
});
@ -2299,7 +2299,7 @@ StorePath EvalState::coerceToStorePath(const PosIdx pos, Value & v, NixStringCon
}
std::pair<DerivedPath, std::string_view> EvalState::coerceToDerivedPathUnchecked(const PosIdx pos, Value & v, std::string_view errorCtx)
std::pair<SingleDerivedPath, std::string_view> EvalState::coerceToSingleDerivedPathUnchecked(const PosIdx pos, Value & v, std::string_view errorCtx)
{
NixStringContext context;
auto s = forceString(v, context, pos, errorCtx);
@ -2310,21 +2310,16 @@ std::pair<DerivedPath, std::string_view> EvalState::coerceToDerivedPathUnchecked
s, csize)
.withTrace(pos, errorCtx).debugThrow<EvalError>();
auto derivedPath = std::visit(overloaded {
[&](NixStringContextElem::Opaque && o) -> DerivedPath {
return DerivedPath::Opaque {
.path = std::move(o.path),
};
[&](NixStringContextElem::Opaque && o) -> SingleDerivedPath {
return std::move(o);
},
[&](NixStringContextElem::DrvDeep &&) -> DerivedPath {
[&](NixStringContextElem::DrvDeep &&) -> SingleDerivedPath {
error(
"string '%s' has a context which refers to a complete source and binary closure. This is not supported at this time",
s).withTrace(pos, errorCtx).debugThrow<EvalError>();
},
[&](NixStringContextElem::Built && b) -> DerivedPath {
return DerivedPath::Built {
.drvPath = std::move(b.drvPath),
.outputs = OutputsSpec::Names { std::move(b.output) },
};
[&](NixStringContextElem::Built && b) -> SingleDerivedPath {
return std::move(b);
},
}, ((NixStringContextElem &&) *context.begin()).raw());
return {
@ -2334,12 +2329,12 @@ std::pair<DerivedPath, std::string_view> EvalState::coerceToDerivedPathUnchecked
}
DerivedPath EvalState::coerceToDerivedPath(const PosIdx pos, Value & v, std::string_view errorCtx)
SingleDerivedPath EvalState::coerceToSingleDerivedPath(const PosIdx pos, Value & v, std::string_view errorCtx)
{
auto [derivedPath, s_] = coerceToDerivedPathUnchecked(pos, v, errorCtx);
auto [derivedPath, s_] = coerceToSingleDerivedPathUnchecked(pos, v, errorCtx);
auto s = s_;
std::visit(overloaded {
[&](const DerivedPath::Opaque & o) {
[&](const SingleDerivedPath::Opaque & o) {
auto sExpected = store->printStorePath(o.path);
if (s != sExpected)
error(
@ -2347,25 +2342,27 @@ DerivedPath EvalState::coerceToDerivedPath(const PosIdx pos, Value & v, std::str
s, sExpected)
.withTrace(pos, errorCtx).debugThrow<EvalError>();
},
[&](const DerivedPath::Built & b) {
// TODO need derived path with single output to make this
// total. Will add as part of RFC 92 work and then this is
// cleaned up.
auto output = *std::get<OutputsSpec::Names>(b.outputs).begin();
auto drv = store->readDerivation(b.drvPath);
auto i = drv.outputs.find(output);
if (i == drv.outputs.end())
throw Error("derivation '%s' does not have output '%s'", store->printStorePath(b.drvPath), output);
auto optOutputPath = i->second.path(*store, drv.name, output);
// This is testing for the case of CA derivations
auto sExpected = optOutputPath
? store->printStorePath(*optOutputPath)
: DownstreamPlaceholder::unknownCaOutput(b.drvPath, output).render();
[&](const SingleDerivedPath::Built & b) {
auto sExpected = std::visit(overloaded {
[&](const SingleDerivedPath::Opaque & o) {
auto drv = store->readDerivation(o.path);
auto i = drv.outputs.find(b.output);
if (i == drv.outputs.end())
throw Error("derivation '%s' does not have output '%s'", b.drvPath->to_string(*store), b.output);
auto optOutputPath = i->second.path(*store, drv.name, b.output);
// This is testing for the case of CA derivations
return optOutputPath
? store->printStorePath(*optOutputPath)
: DownstreamPlaceholder::fromSingleDerivedPathBuilt(b).render();
},
[&](const SingleDerivedPath::Built & o) {
return DownstreamPlaceholder::fromSingleDerivedPathBuilt(b).render();
},
}, b.drvPath->raw());
if (s != sExpected)
error(
"string '%s' has context with the output '%s' from derivation '%s', but the string is not the right placeholder for this derivation output. It should be '%s'",
s, output, store->printStorePath(b.drvPath), sExpected)
s, b.output, b.drvPath->to_string(*store), sExpected)
.withTrace(pos, errorCtx).debugThrow<EvalError>();
}
}, derivedPath.raw());