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60b7121d2c
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>
67 lines
2 KiB
C++
67 lines
2 KiB
C++
#include "installable-value.hh"
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#include "eval-cache.hh"
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namespace nix {
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std::vector<ref<eval_cache::AttrCursor>>
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InstallableValue::getCursors(EvalState & state)
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{
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auto evalCache =
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std::make_shared<nix::eval_cache::EvalCache>(std::nullopt, state,
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[&]() { return toValue(state).first; });
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return {evalCache->getRoot()};
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}
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ref<eval_cache::AttrCursor>
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InstallableValue::getCursor(EvalState & state)
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{
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/* Although getCursors should return at least one element, in case it doesn't,
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bound check to avoid an undefined behavior for vector[0] */
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return getCursors(state).at(0);
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}
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static UsageError nonValueInstallable(Installable & installable)
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{
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return UsageError("installable '%s' does not correspond to a Nix language value", installable.what());
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}
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InstallableValue & InstallableValue::require(Installable & installable)
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{
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auto * castedInstallable = dynamic_cast<InstallableValue *>(&installable);
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if (!castedInstallable)
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throw nonValueInstallable(installable);
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return *castedInstallable;
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}
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ref<InstallableValue> InstallableValue::require(ref<Installable> installable)
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{
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auto castedInstallable = installable.dynamic_pointer_cast<InstallableValue>();
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if (!castedInstallable)
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throw nonValueInstallable(*installable);
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return ref { castedInstallable };
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}
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std::optional<DerivedPathWithInfo> InstallableValue::trySinglePathToDerivedPaths(Value & v, const PosIdx pos, std::string_view errorCtx)
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{
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if (v.type() == nPath) {
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auto storePath = v.path().fetchToStore(state->store);
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return {{
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.path = DerivedPath::Opaque {
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.path = std::move(storePath),
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},
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.info = make_ref<ExtraPathInfo>(),
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}};
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}
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else if (v.type() == nString) {
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return {{
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.path = DerivedPath::fromSingle(
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state->coerceToSingleDerivedPath(pos, v, errorCtx)),
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.info = make_ref<ExtraPathInfo>(),
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}};
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}
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else return std::nullopt;
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}
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}
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