mirror of
https://github.com/NixOS/nix
synced 2025-06-25 06:31:14 +02:00
c98026e982
This adds a setting 'lazy-trees' that causes flake inputs to be
"mounted" as virtual filesystems on top of /nix/store as random
"virtual" store paths. Only when the store path is actually used as a
dependency of a store derivation do we materialize ("devirtualize")
the input by copying it to its content-addressed location in the
store.
String contexts determine when devirtualization happens. One wrinkle
is that there are cases where we had store paths without proper
contexts, in particular when the user does `toString <path>` (where
<path> is a source tree in the Nix store) and passes the result to a
derivation. This usage was always broken, since it can result in
derivations that lack correct references. But to ensure that we don't
change evaluation results, we introduce a new type of context that
results in devirtualization but not in store references. We also now
print a warning about this.
69 lines
2.1 KiB
C++
69 lines
2.1 KiB
C++
#include "nix/cmd/installable-value.hh"
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#include "nix/expr/eval-cache.hh"
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#include "nix/fetchers/fetch-to-store.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 = fetchToStore(state->fetchSettings, *state->store, v.path(), FetchMode::Copy);
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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->devirtualize(
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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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